Is a frog an animal or an insect? A detachment of tailless amphibians. Frog animal. The frog's lifestyle and habitat What group do frogs belong to?

The frog (Rana) is a representative of the class of amphibians belonging to the order Tailless, the family of true frogs.

Description of the frog

All representatives of frogs do not have a pronounced neck; their head seems to have grown together with a wide and short body. The absence of a tail is reflected in the very name of the order to which these amphibians belong. On the sides of the large and flat head are bulging eyes. Like all land vertebrates, frogs have upper and lower eyelids. Under the lower eyelid you can find a nictitating membrane, the so-called third eyelid.

Behind each eye of a frog there is a place covered with thin skin (tympanic membrane). Two nostrils, which have special valves, are located slightly above the huge mouth with small teeth.

The front legs of the frog, equipped with four toes characteristic of all amphibians, are quite short. The hind legs are highly developed and have five toes. The space between them is covered with a leathery membrane; the fingers of the limbs do not have claws.

The only excretory opening located in the back of the body is the cloacal opening. The frog's body is covered with bare skin, thickly lubricated with mucus, which is secreted by special subcutaneous glands.

The frog's size ranges from 8 mm to 32 cm, and the coloring can be either single-color (brown, yellow, green) or variegated.

Types of frogs

The entire diversity of these amphibians is represented by subfamilies:

• toad frogs;
• shield-toed frogs;
• African wood frogs;
• real frogs;
• dwarf frogs;
• disc-toed frogs.

In total, there are more than 500 species of frogs in the world. In the territory Russian Federation the most common are pond frogs and grass frogs. The world's largest frog reaches a length of 32 cm - this is the Goliath frog. The smallest frog in the world is the leaf frog, measuring 2 cm. In general, all types of frogs amaze with their diversity in size and color.

Where does the frog live?

The distribution area of ​​frogs is huge. Due to the fact that representatives of this species are cold-blooded, it does not include areas with a critical climate. You will not find a frog in the sandy deserts of Africa, on the ice fields of Taimyr, Greenland and Antarctica. Some New Zealand islands were once not part of the frog's native areas, but now have distinct populations of the animals. The distribution of some species of frogs can be limited by both natural causes (mountain ranges, rivers, deserts, etc.) and man-made ones (highways, canals). In tropical conditions, the diversity of species is much greater than in areas with temperate or cold climates. There are certain species of frogs that are quite capable of living in salt water or even in the Arctic Circle.

Frogs are a very large group of tailless amphibians; this word often means any amphibian without a tail. But from a scientific point of view, it would be correct to use this word only for representatives of the family of true frogs: amphibians from other families usually have different names (toads, tree frogs, dart frogs, etc.). There are 555 species of true frogs in the world, and their closest relatives are representatives of the copepod family, of which there are 230 species.

Sardinian disc-tongue frog (Discoglossus sardus).

In general, frogs have a body structure typical of tailless amphibians: a large head, a wide toothless mouth, bulging eyes, and long hind limbs. Swimming membranes are located between the toes of the front and hind paws, and there is no tail. In general, these animals look more graceful and thin-bodied compared to toads; in some species, the dorsal side of the body has a characteristic kink (“hump”), by which frogs can be unmistakably distinguished from toads.

The leopard frog (Rana pipiens) has a characteristic kink in its back.

At the same time, different types of frogs differ greatly in structural details. For example, copepods have a flattened body, as if crushed, but piglet frogs, on the contrary, look bloated.

Chocolate white copepod (Nyctixalus pictus).

In some species the snout is oblong, in others it is rounded and looks blunt, and in Darwin's rhinoderma it is generally elongated into a pointed proboscis.

Hairy frog (Astylosternus robustus).

The toes of real frogs have small, prehensile claws; copepods have suction cups. This structure of their paws brings them closer to poison dart frogs and tree frogs. A hairy frog whose thighs are covered with... fur looks very unusual. Of course, this fur is not real wool, but an accumulation of thin skin outgrowths that improve gas exchange. The ability to breathe through the skin is inherent not only in hairy frogs, but also in all other frogs, although to a somewhat lesser extent.

Like all amphibians, the skin of these amphibians is thin and constantly moist due to the mucus secreted. The composition of mucus is species-specific and has very different chemical properties among different species. In all frogs, mucus performs a protective function, as it contains bactericidal substances that kill pathogens. In some species it can also be conditionally toxic (unpleasant to the taste for predators), but real frogs are not deadly poisonous (this is typical of other amphibians - dart frogs). By the way, modern research tropical frog species have shown that their mucus can be used to produce antibiotics.

Spotted piglet frog (Hemisus guttatus).

Most often, frogs have a protective color - brown, gray, green, with dim spots and streaks that perfectly camouflage them among the greenery, in the thickness of silt or fallen leaves. But among them there are also very bright species. For example, the tomato frog is bright orange or red in color. This coloring is not accidental, because this species is classified as conditionally toxic. The mucus of the tomato frog is irritating and very sticky; there are known cases where a snake that attacked this frog had its jaws stuck together.

Tomato frog, or tomato frog (Dyscophus antongilii).

But the glory of the tomato frog pales in comparison to even more amazing creatures - glass frogs. This genus of frogs has several species, which are united by one amazing property - the skin of their abdomen is completely transparent!

Through the transparent skin of the abdomen of the dotted gecko frog (Centrolene prosoblepon), internal organs and maturing eggs are visible.

The sizes of these amphibians vary widely: most species have a body length of 7-15 cm, the smallest frog is the Cuban whistler, or Cuban dwarf, which reaches only 8.5-11.8 mm, and the largest species is the goliath frog up to 32 cm long. The average weight of a goliath frog is 3-3.5 kg, but specimens up to 6 kg are known!

The goliath frog (Conraua goliath) is used as food in Cameroon and Equatorial Guinea. Due to widespread extermination, it has become very rare.

Males are always 1.5-2 times smaller than females; in addition, they can be brighter in color and have special resonator sacs for producing sound signals.

Frogs can be found on all continents except Antarctica: in Europe, for example, their range reaches the Arctic Circle, and they are also found on remote oceanic islands (Hawaiian, Seychelles, etc.). They live in a wide variety of landscapes: on the banks of fresh water bodies (rivers, lakes, ponds, swamps), in forests, mountains, partly in the tundra and deserts. Moreover, frogs living in tropical forests can live in the litter or on tree branches and are not tied to bodies of water, since they make do with moisture from the soil or that accumulated in the leaves of plants. Frogs living on the banks of reservoirs spend part of their time on land (for hunting), and part of their time in the reservoir (for rest and protection from enemies). Different species of frogs have different peaks of daily activity: some species are active primarily at night, others are active throughout the day to approximately equal degrees.

Frogs are solitary animals with no social connections. For the most part, they live sedentary lives, but during the mating season they can make short migrations to bodies of water for spawning. Species living in the temperate zone hibernate during the winter. To do this, amphibians hide in rodent holes, piles of fallen leaves, or lie at the bottom of reservoirs. Frogs hibernate, depending on their habitat, in September-October, and wake up in March-April (in the tundra in May).

The pond or edible frog (Rana esculenta) simultaneously hunts and hides. Frozen motionless in anticipation of prey, it remains invisible to predators thanks to its camouflage green coloration.

Typically, frogs sit motionless, looking for prey. By the way, their brain is designed in such a way that it picks up signals only from moving objects, so these animals spend a lot of time in ambush, waiting for flying insects. Seeing prey, the frog throws out a long sticky tongue, and, if necessary, makes a jump towards the prey. Compared to toads, frogs are much more mobile; they move in fast jumps up to 3 m long! Copepod frogs that live in trees, thanks to the suction cups on their legs, can stay on vertical surfaces and... fly! It was not for nothing that they were called copepods, because these animals have especially wide membranes between their toes, with the help of which they glide from tree to tree.

what group do amphibians belong to and got the best answer

Reply from (*:*)[guru]
The group of amphibians belongs to the most primitive terrestrial vertebrates, occupying an intermediate position between terrestrial and aquatic vertebrates...

What animals are called amphibians? Why?
- Another name for amphibians - amphibians - comes from the Greek word meaning “living a double life.” They can live both on land and in water.
There are three groups or orders of amphibians: frogs, salamanders and caecilians. Different kinds Newts are classified as salamanders.
Worms are creatures that live in burrows. They are blind, they have neither legs nor tail. Amphibians breathe with gills when they are young, and then many of them develop lungs.
Amphibians have smooth and sticky skin, supported by wet special mucous glands. Water easily penetrates their skin, so most amphibians dry out and die if they are taken out of the water for too long.
Some frogs take rather strange care of their eggs. A female tree frog from Brazil builds a nest of mud for her eggs while the male sits and croaks. The Suriname toad carries eggs on its back.

Answer from 2 answers[guru]

Hello! Here is a selection of topics with answers to your question: what group do amphibians belong to?

One of the largest families of the order of tailless amphibians, uniting more than 400 species included in 32 genera. The extremely diverse amphibians of this family are characterized by the presence of teeth on the upper jaw, cylindrical, unexpanded (or slightly expanded) transverse processes of the sacral vertebra, and the absence of intercalary cartilages between the phalanges of the digits. The eastern hemisphere should be considered the probable center of origin of amphibians of this family, with Africa becoming the place of their greatest differentiation. Nowadays they are distributed throughout the world, with the exception of the Arctic regions, Australia and the extreme south of South America.

The most extensive genus - true frogs (Rana) unites more than 200 species. This includes both very small species with a maximum body length of up to 30 mm, and the largest of the tailless amphibians - the goliath frog, reaching 326 mm.

lake frog(Rana ridibunda) is the largest species among the amphibians of our fauna. Its largest size is 170 mm. Females are always larger than males. However, in different places In their habitat, the sizes of animals change noticeably. Lake frogs reach their maximum sizes, living between 45-50° N. w. and 30-50° E. d. In other words, the largest individuals live in the center of the range, which apparently has the most favorable living conditions for the species. As it moves towards the boundaries of its range, the size of the lake frog decreases. Thus, in the Volga delta, the largest females reach 149 mm, and males 128 mm. To the north, in the Voronezh region, the largest females have a body length of 1P mm, and males 112 mm. In Turkmenistan, whose territory lies in the desert zone, along the southern border of the species’ distribution, the largest lake frog caught reached 88 mm. The sizes of animals change not only in different parts range, but also in different habitats, slightly distant from each other. For example, lake frogs inhabiting the outskirts of Astrakhan turned out to be larger than frogs of the same age living about 80 km away from them - in the lower zone of the Volga delta. The difference in body length in young females was 20-25 mm, and in males 30 mm. Apparently, smaller frogs were in worse nutritional conditions.

The stationary lake frog is not easy to notice among aquatic or coastal vegetation due to the fact that it is colored green, olive or dark brown color with more or less black or dark green spots. Sometimes she has a light stripe along her back. Below it is off-white or yellowish in color, usually with dark spots. During mating time, males develop gray thickenings on the first toe of the front leg - nuptial calluses. In croaking males, gray resonators are visible at the corners of the mouth.

The lake frog is distributed throughout Europe and within our country, penetrating Asia, reaching east to Lake Balkhash. The northern border of its distribution almost coincides with the southern border of the taiga. Here she lives in Kazakhstan, Central Asia, in the Caucasus, in Crimea; outside our country, this species is found in Iran, Asia Minor, Jordan, the United Arab Republic and Algeria, finding here the southern limit of distribution. The lake frog is characteristic of both deciduous forests and steppes. In the south it penetrates into the desert zone, and in the north the edge of its range enters the taiga. Rise into the mountains up to 2500 m.

This frog spends its entire life in or near water, inhabiting a wide variety of types of bodies of water, including large, deep, fast-flowing rivers. When there is high air humidity and high temperatures, for example in Southern Dagestan, it hunts further from the water than in the middle zone. In the vicinity of Yerevan, lake frogs move away from the reservoir by 2-3 m, sometimes up to 15-20 m, and young specimens by 4-5 m.

The close connection with bodies of water allows the lake frog to colonize landscapes that are inaccessible to amphibians, such as deserts.

The lake frog belongs to numerous species. In the Volga delta, in some ilmens used for fish farming, up to 60 thousand lake frogs live. In the Colchis, Alazan-Avtoran and Lenkoran lowlands, the number of these animals reaches several dozen per 100 square meters. m. In Turkmenistan, along a kilometer-long route along the bank of the Karasu River (Baghira region), there were up to 141 individuals of this species. The average population density of frogs in the vicinity of Almaty is from 1000 to 2000, and in the vicinity of Iliysk from 450 to 1000 individuals per 1 hectare. However, obtaining accurate data on the abundance of the lake frog in different parts of its range is a task for future research.

The peculiarities of the daily activity of the lake frog were observed in detail in Southern Dagestan in the summer in the shallow oxbow lake of the Samura River, not far from the place where this river flows into the sea. At any time of the day, the total number of lake frogs floating on the surface of the water and jumping in the thickets of coastal vegetation along the banks of the oxbow lake remains approximately the same. However, twice a day they move to land and back. There are many of them on the shore from 21:00 to 7:00 and from 11:00 to 17:00. The most larger number frogs on land are observed at 1 am and 1 pm. The number of frogs in the water decreases as it increases on land. During the frogs' stay on the shore, their stomachs are filled to the maximum. Coastal thickets turn out to be their main hunting ground. In water, animals lie calmly on the surface or move lazily. During this time, food is digested and the stomach is emptied. A pond is a resting place with the most favorable conditions of temperature and humidity, which at the same time provides reliable shelter from enemies. Appearing on land both night and day, lake frogs turn out to be animals with round-the-clock activity. During daytime activity, frogs constantly go into the reservoir for a short time to replenish the supply of moisture in the body, thanks to this during the day a certain number of frogs are found not only on land, but also in water. At night, during the hours of greatest activity, all frogs are on land and do not go into the reservoir, since at lower temperatures they are not in danger of drying out.

The daily rhythm of behavior of lake frogs is not the same in different parts of their range. Thus, in Turkmenistan in summer, lake frogs are most often found on the shores of reservoirs in the early morning hours, in the evenings and at night. During hot daytime hours, the majority of animals are in the water. Those on land also stop hunting, remaining in the shade and in moist areas among coastal vegetation. The stomachs of most individuals do not contain food at this time. In early March, when the mornings are still fresh, frogs usually crawl ashore no earlier than 9 o’clock, and by 10 o’clock the number of individuals basking in the sun increases noticeably. Between 10 and 16 hours the animals feed intensively, and at this time there are two to three times more of them on land than in the reservoir. By evening, on the contrary, the number of frogs is greater in the water than on the shore. However, already in the second half of March the nights are warm and frogs become active throughout the day.

Consequently, the nature of daily activity also changes between seasons. These changes concern not only the time when animals hunt most vigorously, but also the intensity of hunting. In the Volga delta, immature lake frogs feed little in April, and their stomachs are very slightly full. Gradually they begin to feed more and more often, and until the beginning of August the feeding intensity continuously increases, and then sharply decreases. The same picture is observed in males. They differ from juveniles only in that until the end of May their feeding activity increases very slightly. At this time, activities related to the processes of reproduction prevail in males over all others. Even if they do not fully observe the so-called marriage fast, they eat significantly less than at other times of the year. The activity of females is peculiar. In spring they begin to feed later than young and males, but greatest degree Their stomachs were full in the second half of May. From this time on, their activity begins to decline and by the end of August differs little from the activity of males. On average, young, immature frogs are characterized by the greatest activity in obtaining food during the summer; it is only slightly, about 1/5, less in females, while in males the feeding activity is almost half that of females.

As the temperature drops environment The activity of lake frogs decreases and they go into hibernation. In the southern part of Armenia, hibernation begins at average temperature air 11.5° and average water temperature 8°. Lake frogs overwinter at the bottom of reservoirs, migrating in the fall either to deeper ones or to springs. When moving to wintering sites in autumn, frogs can travel considerable distances. Wintering frogs often accumulate under overhanging banks or hide in underwater vegetation. In different climatic zones, lake frogs go to winter at different times. In the mountains, hibernation begins earlier than on the plain. Thus, in Southern Armenia, lake frogs go to winter in the second half of October, and in the vicinity of Makhachkala they stay until mid-November. Populations living further north also hibernate earlier. Near Kursk, lake frogs cease to be found on land in September - October. In Turkmenistan, a sharp reduction in their activity is noticed by the end of November. However, here it is difficult to talk about real hibernation in the lake frog. Some of them remain active. In the non-freezing spring source in Bagheera, awake frogs were not uncommon even at negative air temperatures (-4°) throughout the year. Most fall into a shallow sleep; Although they are sluggish, they are not deprived of the ability to swim and jump. Disturbed animals move without much difficulty and take refuge in another place. Lake frogs do not hibernate near artesian wells and springs in Southern Armenia either.

The time when lake frogs leave their wintering grounds also varies. In Turkmenistan this is the end of February - beginning of March. Also in early March, lake frogs wake up near Odessa and in the vicinity of Makhachkala, and in the second half of March - near Yerevan. At this time, the average air temperature is about 10°. This species appears near Kursk in April, near Moscow - in May. The timing of frogs' awakening is significantly affected by altitude. So, in the Borjomo-Bakurian region, at an altitude of 1143 m above sea level, they wake up in early May, and at an altitude of 1655 m above sea level - in early June. The young leave for the winter later. Near Yerevan, they linger until the end of November, while the bulk of adults hibernate until the first half of November. In the spring, they wake up from winter sleep somewhat earlier than adults. As a result, the duration of wintering in the lowlands of the Caucasus is 60-90 days, in Turkmenistan - 90-95, near Kiev - 150-180, near Moscow - 210-230.

From the time the frogs first appear until the start of spawning, it takes from one week to a month. In southern populations this interval is apparently smaller than in northern ones. During the breeding season, males stay on the surface of the water, forming large aggregations. They are very active and loud. Their “mating songs” attract females. Egg laying is preceded by mating. The manner of grasping the female is unique in all frogs, including the lake frog. The male grabs her behind his front paws so that his paws converge on the female's chest. This peculiar pairing has great biological significance. It stimulates the simultaneous release of eggs and sperm into the water, increasing the percentage of fertilized eggs during external fertilization. The eggs are deposited in the form of a lump formed due to the gluing of the mucous membranes of the eggs.

The diameter of the lake frog egg is 1.5-2.0 mm, and the entire egg is 7-8 mm. The upper half of the egg is dark brown and the lower half is white.

The number of eggs laid by one female increases to a certain size with increasing body length. Thus, in the Volga delta, frogs with a length of 91-95 mm lay an average of 3916-3989 eggs; in frogs with a size of 106-109 mm, the number of eggs increases to 4540-5195.

The average number of eggs with a female body length of 110-115 mm reaches 5408 - 6818 pieces, with 116-119 mm - 7969-9360 pieces. In frogs measuring 120-126 mi, in some years, fertility decreases sharply, reaching a level characteristic of young females (3614 eggs) just beginning to breed. In other years, the fertility of this size group continues to increase (11,237 eggs), but then it decreases in larger females, reaching 128 mm. The number of eggs in such a female was 2935. As the above figures show, fertility depends not only on the size of the animal, since the number of eggs laid by females of the same size varies from year to year. Apparently, in these cases, the living conditions of the species are affected, which do not remain constant from year to year. The fertility of lake frogs from other parts of the range does not exceed the limits obtained for it in the Volga delta.

Lake frogs spawn eggs in one lump or in separate groups of 3 to 10. The spawning period is extended. It is especially long-lasting in southern populations. This elongation can be determined by the laying of eggs in portions or their non-simultaneous maturation in different individuals. In Turkmenistan, there are probably two clutches per year.

Spawning begins when the average water temperature reaches 15.6-18.6°. This indicates that the lake frog is highly thermophilic. In accordance with the heat-loving nature of these animals, their sperm have high heat resistance. They can withstand heating up to 41.4° without harm. Thermal resistance of sperm does not change in frogs living in different parts of their range.

The rate of development of eggs is closely dependent on the ambient temperature. In Armenia in June, with an average water temperature of 20.4° and air temperature of 21.9°, egg development lasts 7-8 days. In May, with an average water temperature of 16.4° and air temperature of 11.2°, development lasts 9-10 days. On average, based on these two observations, lake frog eggs require 154.4 degree days to develop. In the southeast of Kazakhstan, normal development of eggs occurs at a temperature of 18-24°. In the same area, in reservoirs that are heated differently, the period of development of eggs is not the same.

The length of a tadpole of a lake frog that has just emerged from an egg in Armenia is 7-8 mm, in Turkmenistan - 4.8-5 mm. They already have a rather long tail surrounded by a well-developed fin. The external gills are divided into a series of lobes. These structural features indicate that the tadpoles of the lake frog leave the egg at a later stage of development than in some other tailless amphibians, such as the sharp-faced frog. At this time, the body color of the tadpoles is light yellow or brown. Having reached approximately 30 mm in length, the tadpoles turn noticeably green.

The larvae of lake frogs at first remain in the places where they were born and stay in a group, but then very soon spread throughout the entire reservoir. They can be found in the water column both in shallow and deeper places, both in thickets of plants and in clean water. In deep and large bodies of water, tadpoles usually stay near the shores, where the water is warmer and where it is probably easier for them to forage. They lead a diurnal lifestyle and feed most intensively at 10-12 o'clock. At night, the tadpoles sink to the bottom and hide under stones and vegetation.

Eruption of the mouth and transition to active feeding in Turkmenistan occurs when the larva reaches 16 mm in length. In the Volga delta, tadpoles by this time are 16.8 mm long. In different bodies of water their sizes are not the same. On the hollows they reach 22.2 mm, in the ilmens - 16.7 mm, and in the avant-delta - 11.3 mm.

The nutrition of lake frog tadpoles has been studied using precise methods of analyzing stomach contents in a way that is not possible in any other species of our amphibians. They do not feed on higher plants, as was commonly believed, but mainly on algae. The predominant group of their food consists of diatoms and green algae, most of which are tiny plant organisms, often unicellular. The largest of them are filamentous green algae, very thin and delicate, but have a significant extent. Diatoms and green algae were found in tadpoles in all stomachs examined, accounting for approximately 60% of the weight of the contents. Minor foods include protozoa, rotifers, blue-green algae and flagellates. Random food includes the fruiting bodies of lower fungi (molds), the epidermis (skin) of higher plants, the smallest representatives of round and annelids, mollusks, crustaceans, bryozoans and insects. All of them do not play any noticeable role in the diet of tadpoles.

The organisms fed to tadpoles belong to the group of fouling organisms that live on underwater plants or lead a benthic lifestyle in shallow water. Tadpoles eat few inhabitants of the water column. Most likely, they get into their food when, dying, they fall to the bottom or settle on underwater plants. The unique structure of the mouthparts of tadpoles is perfectly adapted to scraping food from plants or from the bottom. Their small mouth is surrounded by protruding, fringed lips that form a small conical proboscis. The upper lip is smaller and less mobile than the lower lip. The lower one is longer and wider, much softer and more mobile. Along its free edge there are small fleshy papillae in several rows, which apparently have a tactile function. They accumulate mainly in the corners of the mouth. The mouth opening is limited by two strong horny “jaws” resembling a beak. The inner surface of both lips, between their free edge and the beak, forms transverse folds, on the ridges of which, as well as along the free edge of the lips, small black horny denticles appear. Each of the tadpole teeth is one modified epithelial cell. It wears out quickly and is immediately replaced by exactly the same one.

The weight of food eaten by tadpoles increases with their body weight, but not proportionally. While body weight increases 40 times, the amount of food consumed increases only 15 times. This happens because with age the gluttony of these animals decreases. In the Volga delta, in tadpoles 17 mm long, the weight of food averages 5.9% of their body weight, with a length of 35 mm - 5.4%, and with a length of 63 mm - 2.3%, i.e. consumption food during development decreases by about 3 times.

The larval period of development of the lake frog is one of the longest among our tailless amphibians. Despite the fact that their external gills disappear earlier than in other frogs, by 7 days, the buds of the hind limbs appear late - on the 32nd day. The hind limbs are divided into sections by the 59th day and acquire mobility by the 74th day. The forelimbs appear on the 82nd day, and on the 84th day the tail begins to reabsorb. In general, the larval period of development takes 80-90 days, and can be much longer.

But the tadpoles of the lake frog grow faster than those of many other species. Their average growth per day from hatching to metamorphosis is artificial conditions is 1.0 mm. Before metamorphosis, the length of the tadpole in the middle zone is 70-90 mm, in the Volga delta - 55-69 mm, in Armenia and Turkmenistan - 50-52 mm. They are only 15 - 25% smaller than young, mature frogs. During intensive organ formation, the growth rate of tadpoles slows down, amounting to 0.5 mm per day (weight gain is no more than 4.9 mg).

During the period of intensive growth, the increase in tadpole length per day is 0.7-1.5 mm (weight gain 7.6-11.2 mg). In deep reservoirs, growth occurs somewhat slower than in shallow ones.

There is a number of data indicating that the timing of larval development depends on temperature. Thus, in the lake frog in the Moscow region the larval period lasts 80-85 days, in the Kyiv region - 70-75 days, in the Caucasus (lowland) - 55-60 days. In cold mountain reservoirs, tadpoles do not have time to metamorphose and overwinter at this stage of development. Sometimes in deep reservoirs this is also observed near Moscow - at the northern border of the species’ distribution.

The best water temperature for the existence of tadpoles of lake frogs is 18-28°. Maximum temperature water in which they can exist is 43°. At a water temperature of 5-6°, the development of tadpoles stops, and at 1-2° they die.

The speed of metamorphosis is also related to the feeding pattern of the larvae. Under experimental conditions, it was possible to delay the onset of metamorphosis in animal-eating tadpoles by feeding them with algae. Probably, due to the herbivorous nature of lake frog tadpoles, they are characterized by a long period of development.

The amount of food eaten also matters, which is apparently determined not only by the needs of the body, but also by the food supply of the reservoirs. Thus, by the period of metamorphosis, tadpoles developing in the Volga delta front turn out to be larger than those developing in ilmen and hollows. Moreover, throughout the entire time after breaking through the mouth and switching to an active method of feeding, they eat more food per gram of body weight than tadpoles in other habitats.

From the first days of their existence, tadpoles are in a state of metamorphosis, every day acquiring more and more new features characteristic of an adult animal leading a terrestrial lifestyle, and at each previous stage organ systems develop that begin to function at the next one. However, metamorphosis is usually called those changes that occur in direct connection with a change in habitat and lead to the complete loss of larval organs. Metamorphosis in tadpoles of the lake frog, like all others, begins with changes in the intestines, as the body stops feeding, then they are released, breaking through the gill covers, and the forelimbs. Further, the order of changes in the structure of tadpoles in frogs, which, like lake frogs, live in a reservoir all their lives, and in those that come to it only for the breeding season, are not the same. The differences are apparently due to the fact that in the former, when the larvae transform into an adult form, the change in habitat is very insignificant, since the underyearlings remain in the reservoir and come out onto land only to feed. In the larvae of the lake frog, the tail first begins to disappear, the structure of the eyes changes, the mouthparts are rebuilt, and only after that, when the larva takes on the appearance of an adult animal, the organs of water respiration - gills - disappear. In the larvae of terrestrial tailless amphibians, the disappearance of the gills occurs much earlier, following the appearance of the forelimbs. Finally, the structure of the skin changes, and the former tadpole becomes a frog, differing from adults only in size and underdevelopment of the genital organs. Metamorphosis in the lake frog lasts about 5 days.

Newly metamorphosed fingerlings are usually much smaller in size than tadpoles. In Armenia they have a length of 14-15 mm. In the Volga delta, their average size immediately after metamorphosis in July is 26 mm. They go to winter after reaching 30-39 mm in length, and some specimens reach 55 mm. In the Voronezh region, the average size of young of the year leaving for the winter is 20-30 mm, and the largest ones are 32-34 mm. During hibernation, frogs hardly grow at all.

The following year, at the end of May, overwintered fingerlings in the Volga delta have a body length of 40-49 mm, at the end of June - 50-59 mm, and at the end of July - 70-79 mm. Until the end of August, females and some males remain the same size. Some males grow to 80-89 mm. During the following summer, two-year-old males reach a length of more than 90 mm, and females - 90-99 mm. By the age of 5, females are 130-139 mm in length. With age, growth slows down, although it does not stop completely throughout life.

Lake frogs reach sexual maturity in the third year of life, when the body length of males is 80-89 mm, and females - 90-99 mm. In the Voronezh region, sexual maturity occurs in frogs with a length of 70-80 mm, and near Kazan - 60-70 mm. The lifespan of a lake frog in nature is 6-7 years. The mortality rate of underyearlings is especially high. In the summer after metamorphosis, they represent the bulk of the population. In Turkmenistan, in reservoirs near Bagir, it was estimated that in June, young of the year accounted for 62.5% of the entire population. However, in March of the following year their share was only 14.5%.

The number of lake frogs in the same places in different years may change, but this issue has been studied very little. A particularly important role in their life should be played by the drying up of reservoirs during drought, which interferes with the normal growth and development of tadpoles and frogs. However, for those lake frogs that live in fairly deep, permanent bodies of water, this factor is of very little importance. In some cases, young of the year, which go to winter later than adults, die en masse when caught unexpected frosts. Death is also possible in wintering grounds due to lack of oxygen in the reservoir.

The feeding habits of the lake frog display all the characteristic features characteristic of frogs in general. These are animal-eating organisms. The list of foods they eat is very large, most of them are invertebrates, mainly insects. Among them, the first place almost everywhere, wherever the nutrition of this species is studied, is occupied by beetles. Only in the vicinity of the city of Libechov (Czechoslovakia) were Hymenoptera in first place. Diptera are in second place here, as well as near Kazan. Near Makhachkala and in Turkmenistan, second place is occupied by Hymenoptera, and in Armenia - Orthoptera. Be that as it may, the predominant food of the lake frog everywhere turns out to be the most abundant animals.

Existing mainly at the expense of insects, the lake frog, unlike other tailless animals of our fauna, also attacks vertebrates. In some cases, this species preys on small mammals, such as shrews or young voles. There are numerous indications of a frog sitting near the water grasping small birds; its attack on the chicks of a grebe nesting in the water is described. One day a dead frog was found with a downy lapwing chick sticking out of its mouth. They are found in the stomachs of lake frogs and constrictors, and small amphibians (frogs, frogs), and tadpoles, and frogs, including their own. However, mammals, birds and reptiles are rare food items for the lake frog. Tadpoles, frogs and fish fry are the opposite. In some cases, they may constitute a certain proportion in the diet of this amphibian. Thus, their own tadpoles become the main food during heavy floods in the Volga delta, when other food is carried away by water or becomes unavailable. A significant number of fry can be destroyed by the lake frog in fish farms and in rice fields where fish are bred. In a word, with large, artificially created concentrations of juveniles. However, according to observations in Armenia, in the presence of a mass of fish fry and tadpoles, lake frogs continued to eat mainly insects.

Despite the fact that the lake frog is closely associated with water bodies all its life, the importance of terrestrial organisms in its diet is much greater than that of aquatic ones. In the middle zone, ground food makes up 68% of all food found in stomachs, in the Ciscaucasia - 86%, in the vicinity of Makhachkala - 73-95% and in Turkmenistan - 95%. This indicates that the lake frog hunts mainly on land. As we move south into more optimal temperature conditions, the role of terrestrial forms in nutrition increases. This phenomenon is in good agreement with the fact that at high temperatures the lake frog spends more time on land, and at high environmental humidity it moves further away from water bodies.

The diet of the lake frog also contains a high percentage of flying forms (24%). In this regard, among amphibians of the central zone, it is second only to the pond frog (27%). In Turkmenistan, the importance of flying animals in the diet of the lake frog increases sharply. They make up more than 60% of all forms encountered. The ability to grab a flying animal is associated in frogs with the ability to make large jumps, as well as with a unique hunting style. They can quickly throw out an elongated sticky tongue, which is attached to the mouth not by its base, but only by its front end, at lightning speed. Prey stuck to the tongue is pulled to the mouth and grabbed by jaws equipped with small teeth, noticeable only to the touch. In lake frogs, the share of flying food also increases due to their daytime activity, since the activity of flying forms during the day is also greatest.

The range of food consumed by lake frogs varies somewhat not only in different geographical locations, but often also in nearby places. For example, in the vicinity of Makhachkala, aquatic animals accounted for 27% of frogs from a reservoir lying in a semi-desert landscape. The predominant foods here were insects, found in 78% of the opened stomachs (of which 67% were beetles, 39% were dipterans) and 33% were vertebrates. In another reservoir on the mountainside, aquatic animals were rarely found in the diet of frogs (5%). Insects were found in all opened stomachs, of which beetles, Diptera and Hymenoptera were found in 60% of the stomachs. These frogs did not feed on vertebrates. It is interesting that the average degree of stomach filling, calculated as a percentage of body weight, in frogs from the first reservoir turned out to be approximately twice as high as in the second reservoir. Observations were carried out between 12 and 13 hours in one reservoir on May 25, and in the other on May 27.

The diversity of feed composition can vary significantly at the same place in different years. The list of food items for the lake frog in the Volga delta in 1956 included 67 animals, in 1957 - 36, in 1958 - 44, and in 1959 - 21.

Dietary habits also change in different months. For example, in the Volga delta at the beginning of May and at the end of August, insects are found in 30% of stomachs, and the rest of the time - in 70-74%; fish in early May are found in 14% of stomachs, and in other months - in 1-3%. . The occurrence of amphibians in the stomachs of lake frogs is especially high in June - early July (28%), while at other times they are found in 16-20% of stomachs. During the summer, the proportion of aquatic inhabitants in the diet also increases.

Different age groups of the lake frog differ among themselves and in the size of the animals eaten. In all of them, beetles will be the dominant food, but young frogs, and especially fingerlings, feed on smaller forms. Young of the year eat leafhoppers in large quantities, which are 3-4 mm long. These animals are not present in the food of older frogs. Under certain conditions, the lake frog destroys mole crickets in large quantities, and immature frogs and young of the year eat mainly the larvae of this insect. The diet of young frogs, more than that of adults, includes ants and spiders.

Young of the year feed almost exclusively on land. Aquatic organisms make up only 6% of the total food encountered in their food. In immature frogs of older ages they account for 26%, and in adults 38%.

On average, young of the year have the least variety of food - 30 forms, versus 34-55 for older ages. The proportion of their predominant food is slightly higher (90%) than that of frogs of other ages (82-88%). The reasons for these age-related feeding characteristics are apparently that juveniles are limited only to smaller forms, while older ones can eat both small and large animals. In addition, immature frogs hunt mainly on land and only as they increase in size begin to obtain food in large quantities in water. Perhaps the young are more selective about food and less dexterous in hunting. However, these assumptions have not yet been confirmed.

Among all our amphibians, lake frogs attract the most attention from the point of view of assessing their importance in human production activities. This is because they cause harm by eating fish fry. It is necessary to assess the extent of the harm they cause. It turned out that lake frogs in natural conditions eat a very small amount of fish. Their propensity for this food increases significantly where the population density of fry is increased. This happens in reservoirs of artificial fish farming and in rice fields where fish fry are raised, and here, too, any significant number of fry are eaten only in certain places where they are concentrated, for example, at the locks. Consequently, the impact of lake frogs on the productivity of fish farms is very small.

It was assumed that lake frog tadpoles could compete for food with juvenile fish. But the study of this issue showed that these assumptions have no basis.

The tadpoles of the lake frog, forming huge clusters, play a significant role in the cycle of substances in nature. The following numbers give an idea of ​​the number of tadpoles in individual reservoirs: in the ilmen of the Volga delta, there are an average of 9,000 tadpoles per 1 m3 of reservoir. The average seasonal biomass of tadpoles in these reservoirs is 400 g/m3. The biomass of tadpoles in one ilmen can reach a weight of 11.5 tons, and in all ilmens of the Damchiksky section of the Astrakhan Nature Reserve it reaches approximately 2282.5 tons.

This entire mass of tadpoles lives off of diatoms and green algae, which are inaccessible to other vertebrates. Tadpoles, in turn, are eaten by some predatory fish, and from terrestrial inhabitants by snakes and various birds: herons, gulls, terns, ducks, some waders, kingfishers and even birds that are not associated with water bodies in their diet. For example, tadpoles of the lake frog are readily eaten by rollers, magpies, and thrushes.

Tadpoles of the lake frog can play a significant role in feeding poultry.

Many animals also eat adult frogs. These, for example, include catfish, pike perch, pike, ottomans, grass snakes, storks, herons, gulls, terns, grebes, rails, kites, marsh harriers, short-eared snake eagle, buzzards, buzzards, buzzards, house owls, eagle owls, crows, rooks, rollers, shrikes, shrikes, foxes, jackals, badgers, otters and even domestic cats.

Lake frogs, which feed mainly on terrestrial food and are in turn eaten by fish, increase the food supply of reservoirs precisely due to these terrestrial invertebrates, playing the role of an intermediate link. Becoming food for fur-bearing animals and commercial fish, the lake frog turns out to be a useful animal from the point of view economic activity person.

If we add to this the destruction of harmful insects by lake frogs, then this species as a whole will turn out to be much more useful than harmful for humans.

pond frog(Rana esculenta) is clearly distinguished from the lake one by the high internal calcaneal tubercle, more or less laterally compressed. It is usually bright green with a light stripe along the back and more or less black spots. The occurrence of a longitudinal dorsal stripe increases towards the north and east. Unlike lake frogs, among pond frogs there are sometimes individuals with a dark temporal spot (9%). Below, the pond frog is white or yellowish in color with or without dark spots.

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During mating time, males have a dark bump on the first toe of the front leg - nuptial calluses; in the corners of the mouth there are external white or yellowish resonators. In spring, the swimming membranes on the hind legs of males grow significantly less (by 35%) than in brown frogs, and in females they grow slightly more - by 13% instead of 2-8%.

The pond frog, or, as it is often called, the edible frog, is significantly smaller in size than the lake frog. Its maximum length is 100 mm. Towards the north and east, the size of the pond frog decreases.

Inhabits Europe, with the exception of the Iberian Peninsula, Southern France, Greece and the Balkan Peninsula. Within our country, it has a wedge-shaped habitat, tapering towards the east and barely crossing the Volga in its middle course.

Inhabits water bodies mainly of deciduous and mixed forests. In some places, for example in Belovezhskaya Pushcha, it is found in damp forests and away from water. In the steppes it lives only in reservoirs among river Urema.

It almost does not penetrate into the taiga, inhabiting only reservoirs of open landscapes in its southern regions. It rises up to 1100 m in the mountains.

At night in the middle zone, outside the breeding season, only individual pond frogs occasionally appear on the surface of the water. The bulk of animals are located at the bottom of the reservoir, where temperature conditions at this time are most favorable. They float to the surface en masse by 8 a.m. and disappear by 10 p.m. The greatest number of individuals are active between 12 and 16 hours - during the warmest time of the day. During these hours, as observations have shown, frogs feed most of the time. At 6-8 hours, the weight of the stomach contents does not exceed 1.1% of body weight; the maximum occurs at 12-16 hours, when the contents of the stomach make up 14% of body weight. Starting from 20 o'clock, the weight of food eaten drops sharply and by 22 o'clock does not exceed 2% of body weight. The activity of the pond frog, which is constantly in conditions of optimal humidity, depends on the ambient temperature, and on warm nights it may not stop.

In spring, the pond frog is numerous on the surface of reservoirs from 10 a.m. to 10 p.m. The activity curve of this species has a two-peak character. The first peak occurs at 14-16 hours, the second at 20-22 hours. During almost the entire active time, most frogs are in the water, and only in the warmest time of the day do they migrate to the shore or objects floating in the water. Here they are busy hunting, as evidenced by the filling of their stomachs, which amounts to almost 20% of their body weight. This first peak of activity is related to nutrition. During the second peak of activity, at 20-22 hours, the largest number of mating and singing individuals is observed, and the weight of food in the stomach does not exceed 4% of body weight. Consequently, the revival of frogs at this time is associated with the processes of reproduction.

The difference between the spring and summer activity of the pond frog is that in the summer the duration of feeding is longer than in the spring. This is favored by higher air and water temperatures.

During the active period, the pond frog obtains most of its food on land. Aquatic food is of less importance in its diet than that of lake frogs, but many times greater than that of brown frogs. In addition to beetles and dipterans, dragonflies and ants play a significant role in the diet of these amphibians. These predominant foods make up 66% of all those found. Approximately 9% of young pond frogs have mosquitoes, in the destruction of which this species is more important than other frogs. Food common to the pond frog accounts for 43% of all animals found in the pond frog's stomachs. Interestingly, in the lake frog they are 69%. This difference is apparently explained not only by the greater or lesser adherence of species to water bodies, but also different types reservoirs in which pond and lake frogs live. For example, stoneflies and mayflies, which are part of the diet of the lake frog, are absent from the pond frog. This must be due to the fact that these insects lay their eggs in fast-flowing bodies of water occupied by the lake frog, but avoided by the pond frog. The size of the prey also matters. Larger frogs eat larger animals. The pond frog, among our other amphibians, preys on the maximum number of flying insects; more than 26% of animals found in the stomachs of this species belong to them.

Winter hibernation for a pond frog lasts an average of 100 days, 15-25 days longer than for a brown frog, but somewhat shorter than for a lake frog. This is the most heat-loving species among our frogs.

After waking up, pond frogs, like all green frogs, do not immediately begin to reproduce. They usually spawn in the second half of May, later than the lake ones, 15-20 days after awakening. One female lays 2000-3000 eggs with a diameter of 1.5-2 mm. Reproduction is extended, as eggs are laid in several portions. The temperature of the water in which pond frog eggs develop, as a rule, does not fall below 16° and does not rise above 31°. Its development is much faster than that of brown frogs that spawn in early spring. However, the rate of egg development in the experiment under the same conditions in the grass frog is somewhat higher than in the pond frog. Pond frog eggs are more resistant to high temperatures than grass frog eggs. The larvae hatch from the egg at relatively late stages of development, their tail is surrounded by a well-developed fin and has an elongated shape, the external gills are divided into a number of blades. On the 6th day, earlier than in all other frog species, pond tadpoles lose their external gills. On the 30th day, the rudiments of the limbs appear, on the 50th the hind limbs are divided into joints, on the 62nd they acquire mobility, on the 69th the forelimbs become visible, and on the 71st the resorption of the tail begins. Development can take up to 133 days. There are known cases of tadpoles overwintering. Their growth is characterized by significant intensity (on average 0.9 mm per day). By the time of metamorphosis, the length of the tadpole reaches the body length of a sexually mature female. The average size of fingerlings is 30-32 mm, weight 3.4 g.

Pond frog populations are divided into three age groups. The sex ratio is as follows: males 31.4%, females 68.6%. Sexual maturity occurs in the 3rd year.

Fluctuations in the number of this species have been little studied. Unlike brown frogs, they suffer less from drought. However, in the Darwin Nature Reserve for 1947 - 1949. The number of pond frogs has changed significantly, decreasing by 4 times. To a certain extent, this is explained by the local specifics of living conditions. The number of pond frogs falls here in years with low reservoir levels, when the decline in water in June leads to the drying out of small reservoirs and, as a result, the death of tadpoles. According to some reports, when water bodies dry out, pond frogs bury themselves at the bottom and, covered with dried mud, seem to hibernate.

The eggs of the pond frog are eaten by mallards, tadpoles are found among the food of the common gull, adults are destroyed by white-winged terns, bitterns, buzzards, eagle owls, and moorhens.

Also belongs to the group of green frogs black-spotted frog(Rana nigromaculata). Her inner calcaneal tubercle is high, laterally compressed, between the dorsal-lateral folds big number longitudinal cutaneous ribs. On top it is grayish-olive in color with a large number of sometimes merging black spots. A longitudinal light stripe runs along the middle of the back. The underparts are white. Sometimes there are individuals with a dark temporal spot (about 4%). In the corners of the male's mouth, the external resonators are gray or almost white. Maximum body length 95 mm. It decreases as the view moves north and west. The black-spotted frog lives in China, Eastern Mongolia, Korea, Japan and within our country on Far East, north to 55° N. w. It is interesting that in this eastern species large specimens inhabit the eastern part of the range, while in the western species - the pond frog - they live in the west.

The black-spotted frog lives in bodies of water, often in rice fields. Wakes up in late March - early April. Spawning occurs in March - April, usually in the morning. The female lays about 5,000 eggs with a diameter of 1.7 mm. The tadpole before metamorphosis is about 71% of the length of the adult. They leave for the winter in October. In its lifestyle it is close to the lake frog.

Pointy-faced frog(Rana terrestris) is a numerous species in our fauna, belonging to the group of brown frogs. Its inner calcaneal tubercle is high, laterally compressed, and its muzzle is pointed. Above it is brown or grayish with dark spots and dots. This makes it inconspicuous among the grass, rotting leaves, pine needles, sticks and twigs in the places where it usually lives. From the eye through the eardrum almost to the shoulder she has a dark, gradually narrowing temporal spot. This spot well camouflages the frog's eye, which is most easily visible in a hidden animal and betrays its presence. The throat of the sharp-faced frog is whitish, mostly with a marbled pattern. The belly is white or yellowish, in the vast majority of cases without spots. The overall color tone of the sharp-faced frog can vary significantly depending on the temperature and humidity of the environment. In dry and sunny weather, its noticeable lightening is observed. In the north of the Gorky region, there is a popular belief that frogs lighten up when the weather is good. In spring, males develop a bright silver-blue coloration and their entire body becomes swollen and swollen. Among the tailless amphibians of the middle zone, the sharp-faced frog is the only one with such a pronounced mating plumage. On the first toes of the male's front paws there are dark, rough nuptial calluses that are not divided into parts. The swimming membrane on their hind legs is better developed during the breeding season than after it, when the frogs leave the reservoirs. Their relative foot area (foot area divided by body length and multiplied by 50) increases by 80% during the breeding season. In females, the growth of the membrane is much less pronounced. The area of ​​her foot changes by only 8%.

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The maximum size that the frog can reach is 78 mm. However, the usual length of mature individuals is from 51 to 70 mm. Geographical patterns of changes in body length of this species have not been established. However, the body proportions of frogs from different habitats are not the same. For example, the relative length of the hind legs in males increases from south to north; in females such changes do not occur. Frogs from the forest-tundra and tundra do not obey this pattern. They are distinguished by short hind limbs. The body proportions of animals change not only depending on their habitat or gender, but also on age. Thus, in males, the relative length of the legs becomes longer with age. However, in the oldest males, in some cases, the opposite changes are observed; the relative length of the limbs becomes shorter. It is interesting that animals born in different years may differ from each other in body proportions more than those living in different geographical locations. In other words, there are changes in body structure over the years. All this characterizes the complex relationships of organisms with the environment and is important for studying the evolution of a species.

The sharp-faced frog is distributed west to North-Eastern France, lives in Belgium, Holland, Denmark, then the western border of its range gradually turns into the northern, passing through Southern Sweden, Finland, Karelia, and reaches the shores White Sea, passes through the lower reaches of the Pechora, the south of the Yamal Peninsula, passes into the lower reaches of the Yenisei and descends south to Tuva. The southern border runs along Altai, through Northern Kazakhstan, crosses the Ural River at Uralsk, the lower reaches of the Volga, Don, Dnieper, passes through Romania, Hungary, the upper reaches of the Danube and Rhine. Absent in Crimea and the Caucasus.

The sharp-faced frog inhabits forest, forest-steppe and steppe zones. In Northern Kazakhstan it enters the semi-desert and is also found in the tundra. It rises up to 700 m into the mountains. Most of the range of the sharp-faced frog coincides with the range of the grass frog, but the boundaries of its distribution are extended to the south.

Compared to the grass frog, it has slightly lower moisture requirements. Planted in a terrarium on dry sand, grass frogs die on the second or third day, while sharp-faced frogs live for more than a week. In places where humidity is 81-90%, the grass frog is rare (23% of encounters), and the sharp-faced frog is much more common (40.9% of encounters). Apparently, this to a certain extent explains the wider penetration of the sharp-faced frog into the steppe zone.

In the tundra, the sharp-faced frog is much less common than the grass frog. It does not climb the mountains in the Polar Urals. Apparently, its resistance to low temperatures is less than that of grass.

In the forest zone, both of these species should be classified as numerous. On a 100-meter route in coniferous forests, on average you can meet two sharp-faced frogs, and in deciduous forests - four. In the north, the sharp-faced frog is less common than the grass frog, but in the south it predominates over it.

Both species share territory to a certain extent. This is shown by simultaneous calculations of the numbers of sharp-faced and grass frogs on the same routes passing through different biotopes. These observations were carried out in the Kostroma, Vladimir and Gorky regions. In various types of forests and on the steppe slopes, only sharp-faced frogs were encountered; grass frogs were not found here. In the spruce-fir forest, in the rye field among the spruce-fir forest, in the oak forest and in the ravines with small bushes, on the contrary, sharp-faced frogs were absent, but grass frogs were found. And in the Yaroslavl region, as well as in the Darwin Nature Reserve, sharp-faced frogs are more numerous in the green moss forest than in the green moss spruce forest.

The significantly greater association of the sharp-faced frog with pine, rather than with spruce, again confirms its lower demands on moisture. Pine usually grows on sands, the moisture capacity of which is close to 2%, while in loamy and clayey soils, characteristic of spruce and mixed forests, the moisture capacity reaches 15%.

Where the grass frog dominates the common frog, the latter occupies drier habitats. Where the sharp-faced frog is more numerous than the grass frog, it also occupies its biotopes, first of all Various types deciduous forests.

Within its distribution, it is found in very diverse types of deciduous forests, in aspen, linden-oak, oak, beech forests and alder forests. Inhabits floodplain forests and birch groves. Sticks to edges and clearings. In the Volzhsko-Kama Nature Reserve, the largest number of sharp-faced frogs was observed in the aspen forest. Here, in 10 days, up to 165 frogs were caught in a trap ditch, in an oak-linden forest with an admixture of birch, maple, elm, spruce and with abundant grass - 86, and in a birch forest - 32. In a pine-spruce forest, more than 15 frogs were not caught.

In open biotopes of the forest zone, in dry meadows and on steppe slopes, the sharp-faced frog is less common than in forests. Here there is less than one frog per 100 m of the route. However, in floodplain meadows the number of this species is significant - up to 4 frogs per 100 m of the count line. Quite often, the sharp-faced frog lives in swamps, especially on their outskirts; it prefers sedge, but does not avoid sphagnum. In sphagnum bogs, the number of this species is approximately the same as in dry meadows.

The sharp-faced frog belongs to the group of terrestrial frogs and not only spends most of the active period on land, but also, as a rule, overwinters. However, within the limits of its distribution in the steppes and tundra, it does not break connections with water bodies even after the breeding season.

It goes hunting in the evening and actively feeds between 20-22 hours, despite the fact that the air temperature drops at this time. This is due to the fact that the humidity is higher at night. After midnight, activity begins to slowly decline. From 4 a.m. to 6 p.m. it stays at a low level. However, the sharp-faced frog is more likely than other terrestrial vertebrates to be seen active during the day.

In the spring, during the breeding season, when frogs stay in bodies of water or along their banks, the nature of their behavior changes. The period of reduced activity is shortened and lasts from approximately 4 to 10 hours. Frogs are inactive only in the coldest time of the day, and during the day and in the first half of the night they are active. The maximum of their activity, as in summer, develops between 20-24 hours. At this time, the maximum number of mating individuals is observed, the mating song sounds more often and more eggs are laid. In spring, activity associated with reproduction processes suppresses all other activities. Frogs feed little; they experience a “mating fast.”

During the inactive time of day, frogs in the spring hide at the bottom of reservoirs, where temperature fluctuations are less sharp than in the air, and in the summer they hide in wetter places, under fallen trees, in stumps, etc.

In the steppe and tundra, where lake frogs do not leave water bodies even after the breeding season, their spring pattern of activity continues in the summer.

The main diet of the sharp-faced frog consists of beetles. Other foods have different meanings for frogs from different geographical locations. In some cases, a significant proportion of the diet, in addition to beetles, consists of spiders, fillies, bugs and caterpillars; in others, mosquitoes join this food, but the importance of bedbugs decreases, or both mosquitoes and bedbugs disappear, but ants appear. Sometimes all other foods, except beetles, differing in significant diversity, are not often found in the stomachs, in small quantities, and it is difficult to give preference to any of them.

The composition of feed can change not only in different geographical locations, but also in neighboring biotopes. In the forests near Kazan, the dominant food items include beetles (48.9%), spiders (29.2%), grasshoppers (27.7%), caterpillars (15.4%) and bedbugs (14.9%). In the same places in the floodplain, the range of predominant foods is decreasing. These include beetles (72.0%), spiders (44.0%) and caterpillars (16.0%). The rest of the food was found in only 4% of the examined stomachs.

In the diet of sharp-faced frogs, terrestrial animals are very important. In the middle zone they make up 91.2% of all food found in stomachs. It is interesting that in the steppe zone, where the frog constantly stays near water bodies, it feeds exclusively on terrestrial organisms. In the tundra, the importance of aquatic food in the diet of this species increases.

The difference in the food of the sharp-faced frog and the grass frog is determined by the fact that the first lives in drier places than the second. For example, the grass frog eats more terrestrial mollusks, which also stick to more humid places.

Using tagging of sharp-faced frogs, it was possible to establish that the feeding area of ​​an individual individual occupies an area of ​​up to 0.2-0.3 hectares. Usually frogs do not go further than 25-30 m from the place where they were marked. Within this area, the animal constantly moves in search of food. The feeding areas of different frogs living in the neighborhood overlap. The size of the feeding area and the adherence of frogs to it are determined by its feeding capacity. If food supplies become scarce or humidity conditions change, limiting animal activity, frogs undertake migrations, moving to other places. Movements occur gradually at a speed of 3 to 20 per day, and not only feeding areas, but also biotopes can change. Such movements can take place over several weeks or over two or more active seasons.

The feeding intensity of frogs, like other amphibians, depends on the degree of their activity, which is limited by temperature and humidity conditions. The decrease in temperature in the fall leads to the fact that frogs are more and more often found with weakly filled or completely empty stomachs. A gradual weakening of activity ultimately leads to hibernation.

Summer feeding migrations invariably turn into migrations in the fall to wintering areas, which in this species are not clearly expressed.

Most sharp-faced frogs winter on land: in holes covered with leaves, in piles of leaves and needles, under piles of brushwood, in rodent burrows, etc. A smaller number of wintering grounds are found in non-freezing streams, forest rivers rich in springs, and in peat bogs.

They go to winter in the northern regions at the beginning of September, in the south - at the end of October, about two weeks earlier than the grass ones. Term hibernation on average 165-170 days, 10-15 days more than herbal. This is apparently due to the lesser resistance of the sharp-faced frog to low temperatures. The young leave for the winter later than the adults.

Sharp-faced frogs wake up near Kiev in mid-March, near Moscow in mid-late April. In cold springs, leaving the wintering area may be delayed until early May. In the tundra, activity begins much later; sharp-faced frogs begin breeding only in mid-June. Immatures appear later than adults. The activity period of this species during the year in the Moscow region takes 135 days, and in Northern Bukovina - 210.

Sexually mature individuals move from wintering areas to water bodies. These movements take place very quickly in large numbers - within 3-4 days. When gathering in spawning reservoirs, frogs travel considerable distances - up to 800 m. They can walk up to 300 m in a day.

Frogs that come to the pond immediately begin to reproduce. The minimum length of females participating in reproduction is 42.5 mm, males - 43.4 mm. Sexual maturity occurs in the 3rd year. It has been noted that frogs living in humid and warm climates begin to reproduce, reaching smaller sizes compared to frogs living in other climates. Males spend more or less long periods of time in reservoirs, lying in wait for females that have not yet spawned eggs when they come to the reservoir. Some males can remain in the reservoir for up to 20-25 days. Females not only come to the reservoir later than males, but also, having laid eggs, immediately leave it. This explains the fact that in reservoirs there are usually a larger number of single males and only mating females that have not laid eggs. In the midst of breeding on land, you can find either individual females that have not yet laid eggs, moving towards a reservoir, or, on the contrary, females already moving away from it. Males are not found on land at this time.

Frogs leaving reservoirs again travel long distances, but since they feed intensively at this time, restoring the energy expended during the breeding season, their movement speed is low - up to 16 m per day.

In steppe frogs, which do not leave water bodies during the entire active breeding period, the spawning period extends to up to a month, while in forest-steppe and forest populations this takes 10-15 days.

Males gathered in a reservoir to breed form large aggregations. Sometimes in shallow water you can count up to 25 of them per 1 m2. The gurgling cry of these animals creates the illusion of a running spring stream or seems similar to the distant barking of dogs. In some cases, females that have laid eggs are injured after a strong mating embrace. The area of ​​skin torn off by the paws of the male on the chest of the female reaches 4 cm2.

Masonry in the form of one, less often two or three lumps is deposited near the shore in small, unshaded, well-warmed places. It usually lies at the bottom for about a day and then floats up. Often accumulates in one place a large number of eggs laid by many females.

The reservoirs in which sharp-faced frogs spawn are varied, often forested, with a grass-covered bottom. Peat bogs often serve as spawning reservoirs.

One female lays 504-2750 eggs. Their number depends on the age of the animal. As it increases, the number of eggs laid increases. However, this only happens up to a certain limit. In females reaching a size of 69-70 mm, fertility decreases again.

The diameter of the egg is 6-8 mm, the diameter of the egg is 1.5-2.0 mm, but it can be less - up to 1.0 mm.

The water temperature at which egg laying begins is 12.0-14.8°. The emergence of larvae from eggs was observed in Ukraine 3 days after its laying. In Tataria this happens after 5-10 days. When the water temperature changes from 4 to 23°, the tadpoles emerge from the eggs after 8-10 days. Fluctuations in the temperature of the water in which the eggs of the frog develop are very large. It happens that she lies in water, covered with a crust of ice on top. In such cases, the development of eggs is delayed, but they do not die. This is due to the great resistance of eggs to low temperatures. It is also important that the temperature in a lump of eggs during the day is on average 3° higher than the ambient temperature. The minimum difference attributable to the coldest time of day is 1.5°. A fully swollen egg shell contains only about 1% dry matter, the rest is water, which has the highest heat capacity among all other substances. Possessing a large heat capacity and concentrating light and heat rays on themselves, like collecting lenses, the transparent mucous membranes of eggs accumulate a large amount of heat. Thermal inertia in a lump of caviar is also explained by the low thermal conductivity of the shells. The caviar heats up more and faster than water, but it takes longer to cool down. Enhanced absorption of heat rays is also facilitated by the accumulation of dark pigment on one pole of the egg, facing the light. At the same time, the pigment serves as a screen, protecting the egg from the harmful effects of ultraviolet rays.

The hatching of a tadpole from an egg occurs thanks to an enzyme that dissolves the egg shells, which is secreted by the unicellular glands of the embryo.

Throughout their life, the tadpoles of the sharp-faced frog form clusters and do not spread throughout the reservoir, sticking to shallow waters.

Very little is known about their diet. They probably prefer animal food. Their oral funnel is less deep, the fringe along its edges is shallow, and the horny jaws are much narrower than those of the herbivorous tadpoles of the lake frog. The teeth on the lips are usually small.

A newly hatched larva has barely defined body parts. The head is separated from the body by a slight interception, and the posterior end of the embryo is extended into a short tail. The tail is surrounded by a wide fin that runs along the back of the larva. The tadpoles are colored black and reach 5.5-7.5 mm in length.

Soon after hatching, external gills develop and are of considerable length. They are highly branched and last longer than those of our other frogs. All this is apparently due to the fact that, living in large aggregations, tadpoles experience a lack of oxygen.

In the first half of larval development, before the appearance of the rudiments of the limbs, when the processes of formation of various organs are intensively underway, the tadpoles of the sharp-faced frog increase by 0.4 mm per day. The growth of an animal reaches its greatest intensity in the period of time from the appearance of the rudiments of the limbs to the division of the hind limbs into sections, that is, just at the time when the processes of morphogenesis are approaching the end and weakening. At this time, the larvae increase by approximately 0.7 mm per day. Then the growth rate drops again, and before metamorphosis, the tadpoles grow by 0.4 mm per day.

Among our other frogs, the sharp-faced frog is characterized by the least intensive growth.

Before metamorphosis, the body length of tadpoles (35-45 mm) is about 67% of the body length of an adult female. Their: relatively small sizes are in accordance with the short larval development. The entire larval development takes an average of 60-65 days, but in exceptional cases it can stretch up to 120 days. Duration of metamorphosis is 4 days. Tundra populations of sharp-faced frogs are distinguished by very rapid development. Its maximum duration is 45-55 days, despite the fact that the temperature of the water in which the tadpoles live is far from optimal.

Newly metamorphosed fingerlings have a body length of 13-20 mm. The northern forms in this respect apparently do not differ from the southern ones. Sex in different zones is differentiated at different stages of development. In populations living in the steppe Trans-Urals, it is already distinguishable in young of the year 19-20 mm long. In the forest-steppe, forest, forest-tundra of the Trans-Urals and in the mountains of the Southern Urals, sex can be distinguished only in the second summer of their life, and in the tundra even later. Apparently, the formation of sex is influenced by the ambient temperature. The lower it is, the later the sex of the animal is differentiated.

From the moment of metamorphosis until leaving for the winter, frogs in the Volzhsko-Kama Nature Reserve grow by an average of 3.4 mm, and in 6 winter months- only 1.1 mm. Their growth in winter is 8 times slower than in summer. In the Southern Urals, young frogs grow from 13 to 24-25 mm in the first summer of life. Frogs from the Polar Urals that have just completed metamorphosis also have body sizes of about 13 mm, but during the first summer they do not have time to reach the size of their southern relatives. And in the future they apparently grow more slowly than them. This is indicated by the maximum sizes of sharp-faced frogs noted in the tundra: frogs (55.4 mm) and southern frogs (60.2 mm).

The resettlement of young fish from water bodies, as a rule, begins at the end of June - in July and occurs at a relatively high speed. These tiny animals cover 25-60 m per day.

In the spring frog population, three age groups are clearly distinguished by size: one-year-old frogs with a length of 25 mm, two-year-old frogs with a length of up to 42 mm, and older ones with a size of more than 42 mm. The ratio of the numbers of these age groups is apparently not the same in different years. In Darwinian and Volzhsko-Kama Nature Reserves in 1947 and 1950 The predominant group was the second. However, in 1936, near Zvenigorod, the third group was the most numerous. The ratio of these age groups also changes within one season. All these changes are explained by different rates of death of frogs, which occur under the influence of various causes.

Adult frogs are eaten by lake frogs, snakes, vipers, storks, loaves, little bitterns, river gulls, lesser spotted eagles, buzzards, crows and even wood grouse. In badgers, these frogs are found in 56% of the examined stomachs and attack frogs and otters, minnows, weasels, foxes, hedgehogs and even common shrews and moles. However, in these animals they are found in only 0.6-19% of stomachs.

In folk medicine, dried frog caviar is used to treat erysipelas of the face.

grass frog(Rana temporaria) by appearance very similar to the sharp-faced one, but differs from it more large sizes(up to 100 mm), dark marble-like pattern on the belly, blunt muzzle and low internal calcaneal tubercle. During mating time, the male’s throat turns blue, and on the first toe of the front legs four-part black rough tubercles become clearly visible.

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Inhabits all of Europe, excluding the Iberian Peninsula, reaching the north to the continent, the southern borders of its distribution are the south of France and Italy. Absent in Crimea, the Caucasus and the lower reaches of the Volga. To the east it barely crosses the Urals. It rises up to 3000 m into the mountains. A typical forest form, in Europe the grass frog is also found in the forest-steppe, entering the steppes only along river floodplains. This numerous species spends the entire summer on land, moving considerable distances away from bodies of water, but inhabiting only wet biotopes.

The distribution of grass frogs on land is determined by their dependence on humidity. In this respect they occupy an intermediate position between green frogs and toads. They are able to lose more water without harm than pond frogs, but significantly less than toads, especially green ones. The permeability of their skin to water is also less than that of toads, but greater than that of the pond frog. The degree of permeability of the skin to water regulates its release by the body into the environment. The skin of animals that have been exposed to the sun allows the least water to pass through, when a thin film of dried mucus forms on top of the body. Skin permeability also varies geographically. Grass frogs from areas with higher humidity have skin that is more permeable to water.

At the northern limits of its habitat, due to low air temperatures and in the south, where there is great dryness, the grass frog stays near the water.

Like other amphibians, it avoids salty bodies of water and cannot live more than a day in water whose salinity reaches 0.07%.

The distribution of the grass frog among biotopes was discussed when characterizing the lifestyle of the sharp-faced frog. Let us only add that the sharp-faced frog pushes the grass frog in the general direction from southeast to northwest. The main reasons for the retreat of the grass frog appear to be some climate warming and the impact of anthropogenic factors, especially deforestation. As a result, the temperature and humidity change in a direction more favorable for the sharp-faced frog. In this sense, the sharp-faced frog can be considered to follow a cultural landscape that is less favorable for the grass frog.

Grass frogs are rarely seen during the day. At this time, they sit hidden in dense bushes, under stones, in stumps, in thick grass - in a word, where there is more humidity. Often, when you lift fallen trees, you can see one or more frogs underneath them. They sit tightly pressed to the ground, and are in a state of slight stupor. Some time passes before the disturbed animals take flight. During the day, in search of wetter shelters, frogs can move from one biotope to another. Thus, more grass frogs were observed in the wet aspen forest during the day than in the neighboring dry watershed meadow. At night, most of them went out to hunt in the meadow.

Active activity in grass frogs begins with the onset of twilight, it reaches a maximum from 23 to 2 o'clock, then the number of active animals decreases, reaching a minimum at 11 o'clock. Frogs that are awake at night feed intensively. Their stomachs are most full at 4-8 hours, that is, immediately after the night period of activity.

According to some observations, the activity curve of grass frogs, as well as sharp-faced frogs, has a two-peak character. The first peak is observed at 21 - 22 o'clock, then the activity decreases sharply and again reaches the peak at 3 o'clock, after which it gradually falls to reach a minimum by the morning. The break at night occurs at the darkest time, and maximum activity corresponds to evening and morning twilight. This pattern of activity is apparently associated with long nights and, therefore, depends on the time of year and geographical location terrain. On days when the air temperature is higher, there are more hunting frogs. Their greatest activity is observed on July and August nights, which are characterized by the highest air temperatures.

Despite the fact that grass frogs prefer high temperatures, their activity does not occur during the warmest period of the day. This happens because for brown frogs, which are not associated with a body of water outside the breeding season, environmental humidity is crucial. During their activity, the humidity is the highest observed during the day. A good confirmation of this is the well-known fact that after rain and heavy dew, frogs show much more active activity and go hunting during the day. In the Arctic, the grass frog is equally likely to be found active during the day and at night. Young of the year are usually active during the day.

The main role in the nutrition of the grass frog (73%) is played by beetles and Diptera, followed by terrestrial mollusks and Orthoptera. These animals obtain the vast majority of their food on land (94.2%). Consequently, although the list of foods of the grass frog is large (87 forms), the basis of nutrition is made up of an incomparably smaller number of mass organisms.

The grass frog's diet contains about 16% flying animals, i.e., slightly less than that of the sharp-faced frog. This is apparently due to the fact that the sharp-faced frog hunts more often than the grass frog during the day, when there are more active flying insects. At the northern border of the species' range, grass frogs, which are more closely associated with the reservoir, eat a larger number of aquatic organisms. The intensity of nutrition varies at different times of the year. In the spring, during the breeding season, they observe a “marriage fast.” However, this phenomenon has not yet been studied and it has not been clarified whether nutrition is completely absent, how males, females and immature individuals behave in this regard.

With the onset of autumn, the number of frogs with food in their stomachs also gradually decreases. This happens faster in adults than in young people. Grass frogs cease to be active with the onset of regular frosts, when the average daily temperature the air becomes below 6°, and the water temperature exceeds the air temperature and ranges from 6 to 10°.

The young leave for the winter one to two weeks later than the adults. They are also found in mid-November at daytime temperatures of 0°. The different behavior of adults and young of the year is explained by their different resistance to low temperatures. While adults under experimental conditions cannot tolerate body hypothermia below minus 0.4-0.8°, young of the year turn out to be resistant to cooling down to minus 1-1.1°, and perhaps even lower. At lower temperatures, the number of respiratory movements per minute in juveniles is significantly greater than in adults, but with increasing temperature these differences are smoothed out.

Among our amphibians, grass frogs are distinguished by their short period of hibernation. On average it lasts 155 days. Only common newts and toaded firebirds sleep less. The duration of hibernation is related to the animal's relationship to temperature. The body temperature of grass frogs in nature ranges from 6.0 to 24.5°, in sharp-faced frogs - from 10.5 to 27.5°. The range of body temperature fluctuations in the first is 18.7°, in the second - 17°. The grass frog sleeps less in winter, apparently because it lives in the range of lower temperatures and can tolerate a wider range of temperature fluctuations.

The duration of hibernation varies depending on the geographical location of the area. Near Kiev it is 130-10 days, near Moscow - 180-200, near Arkhangelsk - 210-230.

In autumn, when the average daily air temperature ranges from 8 to 12°, and the minimum drops to minus 5°, grass frogs group in places close to their future wintering grounds: in wetlands adjacent to water bodies, in roadside ditches, in thickets sedges along the banks of rivers, etc. They move to wintering places along ditches, streams or heavily moist places, avoiding dry and open spaces. Along streams and ditches, animals move both with the current and against it, and migrate mainly during the day. On the path of their movement, frogs often stop. Their speed of movement on land is on average 3-4 m per minute. The distance covered during the entire migration period, according to available observations, does not exceed 1.5 km. The frogs travel this path in one day. The entire process of accumulation of frogs near wintering sites usually lasts no more than 2-3 days. Autumn aggregation sites are usually connected to wintering grounds by water and lie no further than 100-150 m from them.

During years of high abundance of the grass frog, movements to wintering sites can take the form of noticeable migrations.

The autumn movements of frogs are obviously caused not only by a drop in air temperature below the temperature of water bodies, but also by seasonal changes in the food supply. By this time, terrestrial insects begin to disappear and the role of aquatic invertebrates in the nutrition of frogs increases.

Almost any body of water that does not freeze to the bottom can serve as a wintering place for the grass frog. However, she prefers, first of all, not very rocky, fast-flowing, non-freezing rivers, then peat ditches and swamps with rich silt. The fewest wintering grounds can be found in big rivers, if they do not have quiet backwaters. A strong spring flood makes it very difficult for frogs to exit such rivers onto land. Finally, in large rivers there is more predatory fish, exterminating a significant number of frogs in winter. There are also few wintering grounds in lakes and ponds, especially in heavily polluted, small, stagnant ponds, where animals die from lack of oxygen and large amounts of harmful gases released.

The commonly described burrowing of frogs in mud only applies to the pond frog. Herbal ones are located either simply at the bottom of the reservoir, or under overhanging banks, or in thickets of vegetation, and in running waters and under the stones.

During the winter, the grass frog sits in a very typical position, with its hind legs tucked in, and its front legs seemingly covering its head, with their palms turned outward. At the same time, a dense network of blood vessels is very clearly visible on the palms, as a result of which the palms are always bright pink.

Wintering areas in stagnant bodies of water are usually located near non-freezing drains or springs. Here better conditions aeration and less hydrogen sulfide. In some cases, when wintering conditions turn out to be unfavorable, its location changes during the winter. Movement can occur at a distance of up to 120 m.

In running waters, non-freezing runoff is not a necessary condition for wintering. However, even there, a concentration of frogs is usually observed at the place where a stream or tributary flows into the river.

This arrangement of wintering areas protects amphibians from death - the main danger threatening their well-being in water bodies. Deaths occur as a result of a sharp decrease in the oxygen content in water, which is consumed in the processes of decay of organic residues. Frogs wintering in water can also die when reservoirs freeze to the bottom.

However, if the reservoir does not freeze, then wintering conditions there are optimal for amphibians. There is no threat of drying out here at all, and the temperature never drops below zero, and its fluctuations are insignificant. In peat ditches and pits, the temperature does not fall below 3°, and in some springs where frogs spend the winter, the temperature stays within 6-8° all winter.

The number of grass frogs wintering in one place varies. In some cases these are single individuals, in some cases their number can reach several hundred. Most often there are wintering grounds consisting of two to three dozen specimens. Males, females and juveniles spend the winter together.

Wintering frogs are lethargic, but not without the ability to move. Their stomach is not always empty. In some cases, up to 10% of the animals studied had in their stomachs various aquatic invertebrates, scraps of Elodea, Spirogyra and other algae, as well as seeds and their own skin shed during molting. The assumption that the winter contents of the stomachs of grass frogs represents the remains of food swallowed in the fall is unlikely, since their digestion rate at a temperature of 0.5-2° is 72-120 hours, and the body temperature does not fall below during wintering. Despite the fact that the growth of grass frogs slows down sharply in winter, it, like the development of reproductive products, still does not stop completely. Consequently, the vital processes of frogs during winter sleep do not stop, but only slow down extremely. When body temperature drops, the number of respiratory movements decreases by almost 2 times. Oxygen consumption at the same temperature (20°) during hibernation is 2 times less than during activity. At 0°, the release of carbon dioxide is 20 times less than at 25.5°.

However, slowing down of life activity alone cannot ensure survival in wintering areas under water. In the summer, a frog kept at 2°C dies without pulmonary respiration after 8 days, despite the fact that the animal is depressed and its vital activity is greatly reduced. During hibernation, frogs live only by skin respiration for five months or more. This is possible due to a number of changes in the body. IN summer months By lowering the temperature to 0°, it is not possible to induce hibernation in frogs precisely because of the existence of differences in the structure and physiology of “winter” and “summer” animals. So, since the fall, a reserve nutrient - glycogen - has been deposited in their liver. In winter, the number of capillaries in the skin increases and the affinity of hemoglobin for oxygen almost doubles, the conductivity and excitability of the nerve pathways decreases, positive heliotropism gives way to negative, etc. It is known that at a temperature of about 0° the water content in the tissues of frogs increases, since Its secretion by the kidneys stops, but its entry through the skin continues. Apparently, due to this, the weight of amphibians does not decrease during the hibernation period, and in some cases even increases.

All these facts show that the phenomenon of hibernation is not a simple reaction to a decrease in temperature or humidity, but a complex chain of interrelated changes in the body, developed historically as an adaptation.

Wintering conditions for amphibians in a reservoir are more favorable than on land, however, even here, a significant part of wintering animals die without surviving the difficult season. For example, in 1938, about 20% of the wintering grounds of the grass frog that were under observation in the vicinity of Moscow died completely.

The grass frogs that wake up earlier than others lay their eggs first. On average, they begin laying eggs near Moscow on April 22. Over eleven years of observations, the very first clutches were observed on April 7, the latest - on May 3. Spawning begins very soon after waking up, after 3-5 days. Mating in the grass frog begins on the way to the spawning reservoirs. At this time, in females, all the eggs have already ovulated and are in the last thin-walled, stretched section of the oviduct, ready for laying. In all mature individuals of the species, maturation and oviposition occur more or less simultaneously. Having spawned, the frogs do not stay in water bodies for long, dispersing to their summer habitats. During the breeding season, the size of the swimming membranes on the hind legs increases by more than one and a half times in males. In females, as well as in other frogs, the membranes increase slightly.

The clutch of the grass frog has the typical shape of a lump for all frogs, formed by gluing together the mucous membranes of the eggs and containing from 670 to 1400 eggs. Freshly laid eggs in a reservoir are easy to recognize, since they are a small lump of eggs closely adjacent to each other. Gradually, as the mucous membranes swell, the distance between individual eggs increases and the entire lump acquires a significantly larger volume. The eggs stick together only where they touch; in other places there are channels between them, so that a lump of caviar is similar in structure to a bunch of grapes. The spaces between the eggs facilitate the free penetration of oxygen to each of the developing embryos. These channels are preserved only when the lump is suspended in water. In lumps that have sunk to the bottom, at least part of the channels are disrupted, and the normal development of eggs in these areas is impossible. This is important to consider when developing eggs in laboratory conditions. There should be such an amount of water in the vessels that is necessary for the lump to float freely in it. The oxygen regime of developing eggs is also improved by the fact that algae settle on their mucous membranes, releasing oxygen during photosynthesis.

The early reproduction of grass frogs leads to the fact that their clutches can sometimes be observed in reservoirs that have not yet been completely freed from ice. It has been established that eggs of this species can withstand hypothermia down to minus 6° and do not lose their ability to develop. Despite this, the development of eggs of grass frogs in early spring is possible only thanks to those adaptations that they have in common with the sharp-faced frog.

Having the ability to develop at low temperatures, the eggs of the grass frog cannot withstand temperatures of about 24-25° for a long time without harm to themselves. Some researchers believe that the southern limit of the distribution of the grass frog is determined precisely by this circumstance. Thus, studying it in the Pyrenees, where single representatives of this species live, led to the conclusion that the southern limit of the distribution of the grass frog coincides with the July isotherm of 21°. In England, there are cases where the onset of hot weather during spawning delayed spawning. As a result, a large percentage of dead eggs was observed in late-laid overripe lumps of eggs. It is assumed that with a significant increase in ambient temperature, the embryos die from a lack of oxygen, since the need for it increases with an increase in metabolism, and the shape of the clutch in the form of a large lump prevents the aeration of each egg. However, given the structure of the egg ball described above, this is unlikely. The eggs of grass frogs living in the south of their range are more resistant to high temperatures than those of northern populations.

The rate of development is directly dependent on temperature. The higher it is, the faster development occurs. On average, grass frog tadpoles hatch from eggs 8-10 days after they are laid. In deep, shaded reservoirs, eggs develop approximately four times slower than in well-warmed reservoirs. However, under the same temperature conditions in the experiment, the rate of development of grass frog eggs in comparison with our other frogs turns out to be the greatest.

The development of tadpoles in the grass frog takes 50-90 days. At higher temperatures it happens faster. The temperature optimum lies in the range of 21-26°. However, like the sharp-faced frog, the development of the grass frog in the Polar Urals proceeds very quickly, 43-50 days. The temperature of the water in which tadpoles live ranges from 0 to 22° and is most often 10-15°, i.e., far from optimal. The rapid pace of development in northern populations is an adaptation to existence in places where summer is very short.

In the experiment, under the same developmental conditions, the growth of tadpoles of grass frogs, as well as in other species, reaches a maximum during the period of weakening of the processes of organ differentiation, which occurs mainly during the time from the appearance of the buds of the limbs to the complete division of the hind limbs into sections. On average, the growth rate of grass frog tadpoles is only slightly greater than that of the sharp-faced frog (0.6 mm per day). The size of tadpoles of this species before metamorphosis is small. Their length is only 55% of the length of sexually mature females.

The life of grass frog tadpoles under natural conditions was studied in more or less detail in England in different parts of various reservoirs over the course of three years. Observations were carried out weekly.

For most of their lives, tadpoles live in colonies, forming large aggregations. Their density inside the colony can reach 100 pieces per 100 mm2.

About a month and a half after hatching, they disperse throughout the reservoir, beginning to lead a solitary lifestyle. In some cases, mainly when the number of tadpoles is small, their accumulations disappear much earlier. They feed in shallow waters, among algae, on the plant film covering water bodies, and at their bottom. Colonies move in search of more feeding areas that are not occupied by others. Thus, at the spawning sites, tadpoles either disappear or appear again. It is possible that larger individuals occupy best places habitat, pushing out smaller ones. Over the course of three years, it turned out that tadpoles kept among the algae weighed more than those collected from other parts of the same pond. Precipitation, which contributes to the flooding of shallow waters, such as where spawning usually occurs, also affects the increase in the weight of the larvae feeding here. Typically, tadpoles at spawning sites weigh less than those that have moved to other areas.

With the development of vegetation in ponds, the growth rate of tadpoles accelerates. At the beginning of their lives, they grow more slowly and apparently feed mainly on the bottom.

The number of tadpoles in different years in the same pond, with more or less the same amount of eggs laid, can vary significantly. Thus, the tadpoles inhabiting the pond in 1948 accounted for only 1% of the population in 1947. Their growth rate, even in the same reservoir, also varies from year to year. Despite the fact that in 1948 the tadpoles hatched earlier than in 1947, their maximum weight by May 10 was 2 times less than the weight of tadpoles at the same time in 1947. The highest weight of tadpoles before metamorphosis, according to observations , in all ponds over all years varies from 500 mg to 1 g. In some cases, tadpoles weigh more than 1 g.

As a rule, growth continues until the end of June, and then the weight gain curve of tadpoles sharply declines. At this time, the bulk of the larvae metamorphose and remain in the larval state, apparently lagging behind in growth and development. Weight loss during metamorphosis is a phenomenon characteristic of amphibians. By the end of July, tadpoles cease to be found in water bodies.

However, this most typical course of development can be significantly disrupted. In 1947, in one of the ponds, tadpoles had already reached significant sizes by May 20, 400-500 mg. At the beginning of June, the first fingerlings began to appear. Nevertheless, metamorphosis did not occur in the mass, and the weight of the tadpoles either decreased or increased, remaining at approximately the same level from May 21 to June 29. Then it increased significantly (up to 700 mg), mass metamorphosis began, and by August 1 there were no longer any larvae in the pond. In the same year, in another pond, the development of tadpoles was delayed even more, taking on a catastrophic character. With the exception of a small number that metamorphosed at the end of June, most of the population remained in the larval stage until October, gradually becoming depleted and losing weight. In other years, the number of tadpoles in this pond was very sparse, but they grew and developed quickly. However, the number of metamorphosed fingerlings in this reservoir was small throughout the years. The low productivity of this reservoir is apparently explained by poor feeding conditions for tadpoles. In some ponds, metamorphosis was delayed, despite the immediate growth rate.

The reasons that determine the diversity of tadpole development are still very little known.

After metamorphosis, growth of grass frogs continues for up to three years or more. Sexual maturity occurs in the third year. There are cases where grass frogs in captivity lived to 18 years of age. However, their life expectancy in nature is much shorter - 4-5 years.

The mortality rate is especially high during this period; development. The mortality rate of eggs and tadpoles in total is 80.4-96.8%.

The number of grass frogs varies significantly from year to year. Thus, from 1939 to 1942 in the central zone of the European part of the USSR it increased more than 45 times; on the contrary, from 1936 to 1939 it fell steadily. Changes in numbers can occur simultaneously over a large area. A comparison of the boundaries of the territory where the population of the grass frog decreased in 1936-1939 with the boundary of the drought that occurred during these years showed that drought turned out to be the main cause of death of the animals. The cracked beds of dry ponds were littered with withered black corpses of tadpoles. Drying out of the swamps, early leaf fall and dry forest floor led to the death of a large number of underyearlings and adult frogs.

Another reason determining the decline in the number of grass frogs was severe frosts during the little snow winter of 1938/39. This year, wintering grounds were often found that were frozen to the bottom. The death of amphibians in winter can apparently reach significant proportions. There are indications of a large percentage of their death in the winter of 1928/29. Finally, it is known that the harsh winter of 1828/29 led to a sharp decrease in the number of amphibians in almost all of Europe and their complete disappearance in Iceland.

The grass frog is less sensitive to harsh winters than the sharp-faced frog. This is explained by the fact that it winters in water bodies. However, the sharp-faced frog, as a more dry-loving form, turned out to be somewhat more resistant to drought.

Since drought and frost have different effects on the numbers of these closely related species, changes in their numbers do not always coincide in time and scale.

Grass frogs also die from predators. Frog eggs are eaten by some birds: gray duck, wigeon, mallard, moorhen, godwit, black tern. Tadpoles have been observed in the food of rollers, magpies, fieldfares and white-browed thrushes; adults are included in the food of the common gull, black stork, goshawk, buzzard, honey buzzard, spotted eagle, marsh harrier, eagle owl, great owl, raven, gray shrike, and shrike.

Of the brown frogs, distinguished by a well-developed dark temporal spot extending from the eye through the eardrum, 5 more species live in our country: Siberian(Rana cruenta, or R. chensinensis), Transcaucasian(R. cameroni), Asia Minor(R. macrocnemis), kicking(R. dalmatina) and Far Eastern(R. semiplicata). The biology of these species has been little studied. All of them have a low inner calcaneal tubercle, not laterally compressed. The color of the body above is light brown with more or less dark spots. Siberian and Transcaucasian frogs often have a light stripe along their back. The Siberian frog has blood-red spots on its belly, which is where it gets its Latin name (cruenta means “splattered with blood”). Other species have a plain, red or pink belly. The smallest of them is Siberian, with a maximum length of 66 mm, slightly larger is the Far Eastern one - 79 mm, even larger is the Asia Minor and Quick, reaching 80 mm in length, and the largest is the Transcaucasian, having a length of up to 90 mm. The Asia Minor and quick frogs are also distinguished by the considerable length of their hind legs.

Siberian frog inhabits Siberia, North-Eastern Kazakhstan, Northern Kyrgyzstan, in the Far East it is found in Primorye, Amur Region, Sakhalin and the Shantar Islands. In the west, the border of its distribution runs between 70 and 80° east. d. To the south it descends to Central China, to the north it reaches the tundra. To the east of the Urals along the forest and forest-steppe belt, it seems to replace the grass and sharp-faced frogs. Like the latter, it is found in steppes and semi-deserts. In the southern parts of its range it lives only near water bodies. Available information on the biology of this species was collected mainly in Kazakhstan. The number of Siberian frogs in the vicinity of Almaty is from 500 to 800 individuals per 1 hectare. The main food is insects. In early spring Aquatic insects are often found; at other times of the year, as a rule, only terrestrial ones. Harmful insects make up 50-70%.

The Siberian frog goes to winter in the second half of October - early November. It overwinters in the thickets of swampy reservoirs, in wells-kopans and on land near the water: in pits with rotting vegetation, in soil crevices, in rodent burrows, etc. In the spring it appears in March - early April. Vital for 7-8 months a year. Soon after waking up, no more than 10 days later, it begins spawning. The mating season lasts from two weeks to a month. Males rarely make quiet sounds. Mating takes place underwater. Lays 1000-1600 eggs. The egg is dark brown in color. The diameter of the egg is 1.7-2.3 mm, and the diameter of the eggs is 5-7 mm. The spawning grounds are reservoirs located in river floodplains, shallow, slightly swampy, slow-flowing springs, wells and ditches. Eggs are usually laid at a water temperature of 18°. Tadpoles hatch after 6-10 days, at which time they reach a length of 7-12 mm. Tadpoles, already leading an active lifestyle, are dark gray on top with small spots and specks of brown color; on the underside they are single-colored, gray and their body is very transparent. By the end of development, the length of tadpoles ranges from 37 to 60 mm. They feed on phyto- and zooplankton and detritus. Stern plant origin make up 20-25%. The length of newly metamorphosed fingerlings is 13-17 mm. The young frogs emerge on land in the last days of May. Development takes from 25 to 40 days. Over the course of a month, the size of the fingerlings increases by 7-10 mm and by the end of summer their length reaches 33 mm.

In the southeast of Kazakhstan 20-30 years ago Siberian frog was numerous, but has now noticeably decreased in number. This may be due to the fact that over the past 50 years the lake frog has penetrated into the Balkhash basin, displacing the Siberian frog.

Transcaucasian and Asia Minor frogs are very similar to each other, and the question has repeatedly arisen as to whether they can be considered different species. However, a detailed analysis of their structural features confirms that they belong to different species. This is also evidenced by their physiological characteristics. The muscle tissue of these two species loses excitability at different temperatures, and the Transcaucasian frog turns out to be more resistant to high temperatures. The controversy surrounding these two species has led to the fact that it is still not always possible to decide which of them belongs to certain biological features cited in the literature.

Transcaucasian frog distributed from Southern Dagestan through Eastern Transcaucasia, including Talysh, to the plateaus of Armenia. It rises into the mountains to a height of 3210 m above sea level. Adapted to a land-based lifestyle, the Transcaucasian frog can live with a water loss of up to 29.5% of its total body weight. It stays away from bodies of water, gathering near them only during the spawning period and in the fall before leaving for the winter.

The main food of the Transcaucasian frog belongs to terrestrial forms, 70-80% comes from Coleoptera. About 10% of all specimens encountered are caterpillars. More than 50% of animals eaten are pests.

Transcaucasian frogs overwinter in reservoirs, usually in several copies, burrowing into the silt to a depth of 30-40 cm. Concentration near reservoirs in the fall occurs when the average air temperature reaches 6-7°. Transcaucasian frogs begin to leave for bodies of water at a temperature of 4-5° and disappear completely at 3-4° below zero. In the mountains at an altitude of 1760-2000 m above sea level this happens in early November; at an altitude of 1300 m in the second half of November. Young frogs go to winter later, meeting until the beginning of December at an average air temperature of minus 1-2°.

In spring, Transcaucasian frogs appear at the beginning, and in high mountain areas at the end of March. The duration of their hibernation in different geographical locations varies from 100 to 140 days.

Like other brown frogs, Transcaucasian frogs exhibit greater resistance to low temperatures than green frogs. This is manifested in the fact that they hibernate later than lake frogs and wake up earlier, and also go higher into the mountains. Accordingly, they are more sensitive to high temperatures. Their muscle tissue is more likely to lose excitability when the temperature rises than that of lake frogs. However, if we compare Transcaucasian and grass frogs in this indicator, the former turn out to be more resistant to high temperatures, which is due to their more southern distribution.

Transcaucasian frogs participate in reproduction when they reach 50-55 mm in length. Males make up 60% of the population. This species has a very unique expression of sexual dimorphism, which develops during the spawning period and is expressed in the fact that the mating color of the female is brighter than that of the male. The female's upper body becomes pinkish and her abdomen turns bright orange-red. Males at this time are gray or brownish. Only their lower thighs and the rim of their abdomen are pink. The first toe of the front legs of males is black. Females are larger than males.

During the day, these frogs are invisible in reservoirs. The eggs are spawned at night, in one or less often in two portions. One female lays from 3500 to 5000 eggs. In females with a length of 85 mm, the diameter of the egg is 2 mm, in smaller ones - from 1.5 to 1.8 mm. The water temperature during spawning ranges from 4 to 14°. At an altitude of 980 m above sea level, spawning begins in the second half of March, and at an altitude of 1940 m - at the end of April.

The development of the embryo at a water temperature of 5-8° lasts about 10 days. The dark brown tadpoles that have left the egg shell are 9-10 mm long. On the 2-3rd day after hatching, external gills appear, then the mouth breaks through and the internal gills begin to function. Approximately on the 20-25th day of development, when the tadpoles become 23-25 ​​mm long, the rudiments of the limbs appear. On the 50-55th day, the left forelimb emerges through the gill opening, and the right forelimb breaks through the operculum. The tail resolves within 6-7 days. When water temperature fluctuates from 5 to 23°, development in the Transcaucasian frog lasts 60-70 days. The length of the frog after metamorphosis is 14-15 mm, and before leaving for the winter - 30-35 mm. In lowland areas, fingerlings appear in mid-May, in highland areas - in the second half of June.

Asia Minor frog found in Asia Minor, on the Black Sea coast of the Caucasus and in the Ciscaucasia. Occasionally it is found at altitudes up to 3500-4000 m. In the Borjomo-Bakurian region it is most numerous at altitudes from 1500 to 1700 m. In Azerbaijan, this frog usually lives at an altitude of 700-1200 m. They inhabit mountain forests and forest-steppes, and are found in gardens.

Asia Minor frogs most often gather in water bodies only during the spawning period and for wintering, however, apparently, they do not avoid them at other times. So, in the vicinity of Stavropol during the day they can only be seen in cold water forest streams. In the Borjomo-Bakurian region, they leave the reservoir at 9-10 o’clock, move 40-60 m from the shore and hunt on land until 17-18 o’clock, then gather again on the shore of the reservoir. Young frogs return to the water an hour and a half later.

Asia Minor frogs, to a greater extent than other brown frogs, eat aquatic animals (23.9%), being on a par with green frogs in this indicator. Their predominant food consists of beetles, dipteran larvae and aquatic crustaceans. Among beetles, the first place in the diet of this frog is occupied by the genus Bimbidion, whose representatives always stay near water.

The total percentage of their predominant food is high (72.3%), just like other brown frogs. Flying insects are rarely eaten. However, all this may be characteristic only of young frogs, whose nutrition has been analyzed to a greater extent than that of adults.

During the breeding season, a “marriage fast” is observed.

Asia Minor frogs go to winter in the vicinity of Stavropol and in the Borjomo-Bakurian region at the end of September, in Azerbaijan - in October, and occasionally in early November. They overwinter in large concentrations in quiet springs in gorges. However, there are indications that this frog may overwinter on land.

In the lowlands they appear in mid-March, in the mountains - at the end of April. For this species, the same color changes during the mating season are described as for the Transcaucasian species. During breeding, males rumble quite loudly, reminiscent of grass frogs in their voice.

Fast frog It is distinguished by a slender body, a narrow head and unusually long hind legs. If its hind leg is extended forward, the ankle joint extends well beyond the end of the muzzle. The frog's eyes are large and convex; the eardrum is located very close to the eye and is barely smaller in size. On top, the frog is pinkish-beige or light brown in color with dark spots. On the hind legs, dark spots are arranged in fairly clear stripes. The belly is always white, with a noticeable pink tint in living ones. Some time after being caught, it turns bright pink. During the breeding season, males develop gray nuptial calluses on the first toe. They do not have resonators. The voice is weak.

Agile frogs are extremely mobile. They make jumps of 1-1.5 m in length and up to 1 m in height. When escaping pursuit, they are able to make leaps of up to 3 m.

The frog inhabits the western, middle and southeastern parts of Europe from northeastern Spain and France east to Asia Minor. The northern limits of distribution are Denmark, the islands of Rügen, Bornholm and the extreme south of Sweden; southern limits - the island of Sicily, the Apennine Peninsula and the Peloponnese. In the USSR, the frog is found only in areas adjacent to the Eastern Carpathians. It goes to the mountains up to 1500 m above sea level, but is more often found on the plain. Throughout its range, the frog is not numerous. Leads a land-based lifestyle. Females move further from the water than males. Favorite habitats are meadows with thick and tall grass, forest clearings in beech and mixed forests, thickets of bushes in valleys and, less often, gardens. Does not avoid dry areas, but prefers places with humidity from 65 to 80%. Active at dusk, and in damp places during the day.

The diet of this species is dominated by beetles, spiders, Diptera, Homoptera and Hymenoptera. It forages almost exclusively on land. Aquatic forms are represented by dipteran larvae and cladocerans. Harmful insects make up 41.5% of the number of individuals eaten.

They leave for the winter in mid or late October. They overwinter buried in the silt at the bottom of reservoirs.

In Transcarpathia in the spring they appear in the second half of March, a little later than the grass and sharp-faced ones, which indicates the great heat-loving nature of this species. Caviar does not tolerate low temperatures. Fast frogs begin to mate only when the water temperature rises to 4-5°. One female lays from 600 to 1400 eggs. The diameter of the egg is 2-3 mm, and the diameter of the entire egg is 9-12 mm. The upper half of the egg is brown or blackish, the lower half is yellowish or off-white.

The sperm of the frog are similar to the sperm of the grass frog and are very different from the sperm of the frog, which the frog is more similar to in appearance and anatomical structure.

The development of the tadpole lasts 2-3 months. The maximum length of a tadpole is 55-60 mm. Metamorphosis ends in August. Young frogs that have just completed their metamorphosis have a body length of 13-20 mm.

Like other representatives of the genus, it leads an aquatic lifestyle and tuberous frog(Rana rugosa), living in Japan, Korea and the southern part of Primorsky Krai. It reaches 56 mm in length, its skin is tuberous on top. The upper side of the body is painted a dull gray-brown color, turning into green in the back of the body. The belly is dirty white with black marble streaks. The voice of this frog is a quiet grunt that is heard night and day, both during the spawning period and after it.

Another aquatic frog tropical coastal frog(Rana limnocharis) is widespread in Southeast Asia. It rises up to 2000 m in the mountains. Its length rarely exceeds 50 mm. The upperparts are olive green or olive brown; spotted pattern grass-green or dark brown; the stripe running along the midline of the back is sometimes narrow yellow or grass-green, sometimes wide orange; sometimes it is completely absent. The underside is white, the lips are spotted with dark brown. In tropical Yunnan, it is the most abundant frog species in open landscapes. On the outskirts of rice fields they are found 4 times more than in the adjacent forest. They are active at night when there are more active insects. The population of these frogs is represented by two age groups: young of the year (18-32 mm) and adults (over 34 mm). This species is characterized by rapid growth and early onset of sexual maturity - at one year of age. It is likely that the bulk of the population is renewed after a year, since frogs older than one year make up less than 2% of the population. Reproduction is confined to the rainy season - from May to August. It has very high fertility. The eggs, the size of millet grains, form oval clumps. The tadpoles hatch after 48 hours.

Indian tiger frog(Rana tigrina), which can reach a size of 150 mm, is very similar in color and appearance to the previous species, but differs from it in better developed longitudinal folds on the back, which often protrude acute angle. Used for food. There is a farm near Canton that breeds this frog in artificial ponds.

One of the most beautiful frogs - red-eared frog(R. erythraea) lives on the Malay Peninsula and adjacent islands. It has a slender build and has distinct adhesion plates on the toes of both pairs of limbs. It is green with a metallic sheen on top and dark brown on the sides. The longitudinal folds of the back of this frog are silvery-white, the eardrum is red; The upper half of the iris is golden yellow, the lower half is fiery red. This numerous species lives in ponds, swamps and rice fields. Seasonality in reproduction is not expressed. In males, changes in the intensity of spermatogenesis and in the development of nuptial calluses during the year are insignificant. Eggs at different stages of maturation were also found in females throughout the year. However, the percentage of females and males ready to breed varies in different months from 10 to 50.

U short-legged frog(Rana curtipes), common in the forests of Western India, tadpole development continues from July to March. They feed exclusively on plant foods. By October, their body length reaches 5 cm, and the intestinal length reaches 20 cm. In October - January, morphological differentiation does not occur in tadpoles, but they grow vigorously and in January reach 11 cm (intestinal length 28 cm). By the end of January, the rudiments of the hind limbs appear and intestinal reduction begins. In February, the formation of the limbs ends and the resorption of the tail begins.

Throughout the South and Tropical Africa, as well as in Madagascar and North-East Africa leading an aquatic lifestyle is common Nile frog(R. mascareniensis), reaching 40-48 mm in length. The upper side of her body is olive-green, brown or gray-green with darker spots, the lower side is white; the back of the thighs is white with marble streaks. There may be a light stripe along the back. The Nile frog played a large role in Egyptian mythology. The deity Ka, who had the head of a frog, was one of the modifications of the god of truth Ptah. In addition, there was also the frog-headed goddess Heka, who, together with her husband, the god Khnum, personified water. The frog was a symbol of resurrection. The tadpole represented the number one hundred thousand in hieroglyphic writing. Even embalmed Nile frogs were found in ancient Thebes.

Africa is home to the largest species of frogs known - goliath frog(Rana goliaph), having a length of 250 mm or more and reaching a weight of 3.25 kg. It has a very limited distribution, inhabiting an area approximately 100 km wide along the coast of the Republic of Cameroon and the Rio Muni.

The frogs that inhabit the waters of North America have been studied better than others.

The largest of them is bullfrog(R. catesbeiana) has a length of 200 mm. The strength of the bullfrog's voice is approximately in the same ratio to the strength of the voice of our green frogs as the size of these amphibians. The bullfrog is distinguished by its large size eardrum, which is not inferior in size to the eye, and in males even exceeds it. The olive-brown or olive-green upper surface of the body is covered with large dark brown and black spots; The lower part of the body is yellowish-white, plain or marbled. The iris is reddish with a yellow rim. This species has well-developed swimming membranes and the hind legs reach a length of 25 cm. There are no longitudinal dorsal folds. The bullfrog is common in eastern North America, being more numerous in the south than in the north. Nowhere does it form such large concentrations as our green frogs. Prefers densely bushy banks of rivers that differ clean water. He escapes danger by jumping into the water. The main food is insects, spiders, and mollusks. Depending on gender and by month, the composition of food does not change. As frogs grow, the number of insects in their food decreases, and the proportion of plant residues increases. In reservoirs in open areas, the average weight of stomach contents is greater than in reservoirs located in the forest. Probably, in the first case, prey is more accessible to frogs.

Due to its size, the bullfrog is also a real predator, eating all other animals that it is able to overpower: fish, other amphibians, chicks, etc.

In Canada, tadpole development lasts 2 years. After metamorphosis, in different populations the growth rate, time of puberty, and, accordingly, maximum body sizes are not the same.

Similar to a bullfrog but much smaller in size loud frog(Rana clamitans). The upper side of the body of this frog is colored gray in front and olive green in back; the throat is lemon yellow, the belly is white; the back and front legs are spotted with brown, and the hind legs are in bands of the same color. The skin is rough, rough. Unlike the bullfrog, there are dorsal-lateral folds. The average size of the noisy frog reaches 47 mm. The maximum growth rate is observed in the first year of life, and further increase in its size is insignificant. These inhabitants of reservoirs are not found further than 18 m from the water. Metamorphosis is observed in the first half of July.

Leopard frog(R. pipiens), colored in different shades of green and, like other green frogs, does not have a dark temporal spot running through the eardrum, leads a terrestrial lifestyle, preferring damp places. In this respect it is similar to brown frogs. Its dimensions reach 75-90 mm. It has a wide range, covering most of North and Central America. Due to its high mobility, survival rate and relatively lower requirements for moisture, the leopard frog apparently spreads to the north, northeast and northwest along river valleys, dry valleys and interfluves, displacing a species similar to it in its lifestyle - spotted frog(Rana pretiosa). The latter is more demanding on humidity, but is more tolerant of low temperatures. The penetration of the leopard frog to the north is hampered by its adherence to higher temperatures. Together, these two similar species cannot live long and represent a typical case of sibling species.

In the stomachs of leopard frogs, 15% of the food volume consists of lepidopteran larvae, 9% - snails, 4% - woodlice. There are known cases of bats being in her stomach. In summer, in good weather, leopard frogs usually remain in their shelters 95% of the time of the day, some stay there for more than 24 hours and even up to 5 days. Their movement in individual areas usually does not exceed 5-10 m. Such movements occur at any time of the day, but almost 2/3 of the total distance passes in the dark. The movement of frogs within an individual area forms a complex network of intersections, loops and doubling of routes. During night rains, frogs sometimes undertake significant movements, walking 100-160 m. At dawn, migrations stop, but can continue the next night. One frog walked 240 m in two nights. During heavy, prolonged rains, almost the entire population of frogs migrates. Of the 30 frogs captured and marked during or after the rains outside their individual areas, 25 were later found again in their original places or on the way to them. The highest recorded migration speed is 46.5 m per hour. The distance traveled and the speed of movement are highly dependent on temperature. Metamorphosis in the first half of July.

R. pipiens and R. pretiosa have a low growth rate.

Sticking to damp places, the small brown frog also leads a terrestrial lifestyle - wood frog(R. silvatica), penetrating north in America further than all other amphibian species. Winters on land. IN temperate climate it begins to reproduce earlier than all other species of frogs. In Alaska, its breeding period for 12 years began between April 24 and May 18. During the three days immediately preceding the start of breeding, the average daily temperature is 6.1°. Near the headwaters of the Mississippi River, it breeds in ponds at higher elevations and then disperses into low-lying swamps. Metamorphosed fingerlings also come here.

The sizes of individual plots where they remain all summer average 69.5-72.3 m2. Many frogs, re-captured a year later, were located near the places of last year’s capture: at a distance of 14-29 m. In a spruce-larch, peat bog, the wood frog leads a diurnal lifestyle. The maximum of its activity is observed between 8 and 10 and between 16 and 18 hours. The degree and duration of its activity are directly proportional to air humidity. Young frogs prefer wetter places than older frogs. The growth of these animals is especially intense at a young age and almost stops by the time of puberty. During the breeding season, growth stops. Its pace also slows down when the temperature drops and there is a lack of food. Females, like most other amphibians, grow somewhat faster and reach larger sizes at maturity.

- (Ranidae) family of tailless amphibians. Widely distributed; absent only in South America, South Australia and New Zealand. 6 subfamilies: dwarf, African forest, toad-like, N. l. proper, corymbocactae and discopactaceae... ... Great Soviet Encyclopedia

Frogs (Ranidae), a family of tailless amphibians. Dl. from 3 to 20 and even 32 cm. Teeth on the top, jaws, terminal phalanges of the fingers without intercalary cartilages. The body is usually slender, with long (jumping) hind limbs. 46 genera, 555 species... Biological encyclopedic dictionary Wikipedia

True frogs Scientific classification Kingdom: Animals Type: Chord... Wikipedia

True frogs Scientific classification Kingdom: Animals Type: Chord... Wikipedia

Frogs belong to amphibians, or amphibians. They are poikilothermic (cold-blooded) animals with variable internal temperature body, changing depending on the environment. The frog family is numerous. It includes more than 500 species. It is believed that the homeland of frogs is the eastern hemisphere, and more specifically, Africa. The most species of frogs are found there. Representatives of this family are found almost anywhere on the globe, excluding the Arctic snows, Australia and some areas of South America. The sizes of frogs vary greatly - from 1 to 32 cm. Their color can also be different - from brown, inconspicuous to extremely bright.
Frogs feed on small insects, but sometimes they can eat their own relatives. For hunting, they have a long sticky tongue, with which they knock down dragonflies, midges and other flying creatures in flight.
Frogs are close relatives of toads and toads. All of them form a detachment of tailless amphibians, which is opposed by a second large detachment - tailed amphibians (newts and salamanders).
Frogs have a lot interesting features. So, back in the 18th century. Scientists have found that they absorb oxygen through their skin. Moreover, this process can occur with equal success both on land and under water. On land, frogs breathe through their lungs. However, they also take oxygen through the skin. All amphibians have bare skin containing various glands that secrete mucus and moisturize the skin. But nevertheless, amphibians are attached to a humid environment, although they can be seen not only in water or near water. For example, the widespread European grass frog - like the common toad - appears near water only to lay eggs.
Many species of frogs have special poisonous glands in their skin that produce poisonous mucus. It causes respiratory paralysis in those who try to attack the frog. In other cases, even a small amount of mucus that gets on the skin leads to ulcers and burns.
Frogs have cells in their skin that allow them to change the color of their skin so as not to stand out from the surrounding vegetation. This helps them escape from enemies. Frog skin is very sensitive to sunlight, but at the same time it is not a necessary organ for this amphibian. This is evidenced by the fact that a frog without skin continues to live. Periodically, the frog molts, shedding its old skin, which it immediately eats.
The lungs of a frog, unlike other living creatures, are not used at all to extract oxygen from the air, but to make sounds, which we call croaking, which is produced using sound bubbles in the throat. For better “singing”, frogs also have a pair of resonators. They look like a pair of bags swelling on the sides of the head. Only males “sing” to attract a female.
Frogs lay eggs. Its quantity is amazing! Some species can lay up to 20 thousand eggs at a time. Its frogs lay in water. They often do this in large groups. Frog eggs form large clumps, which in grass and pond frogs contain several hundred eggs. Developing from an egg into an adult, frogs go through a stage of transformation: tailed tadpoles that breathe through gills emerge from the eggs. Gradually, their hind limbs grow first, then their forelimbs. Finally, the rudder tail disappears, and the little frog is ready for life on the shore. Tadpoles hatch after 7-10 days. After 4 months, they become small frogs. At 3 years old they become sexually mature.
If European frogs are rarely larger than 10 cm, then in North America there lives a bullfrog, reaching a length of 20 cm. And the record holder among frogs is the goliath frog living in Africa - its total length is 90 cm, and it can weigh up to 6 kg !

The African tree frog is a champion jumper. With the help of its long and strong hind legs, it can jump 5 m in length.
The African burrowing frog lives in Africa. It can grow up to 25 cm long and weigh up to 2 kg. She lives a long time - up to 25 years. Its large mouth is equipped with sharp and large teeth, with which it grabs its prey - other frogs, small rodents, snakes, lizards, etc. When trying to grab it, it can bite. The hind limbs of this frog are very strong. She needs them to dig deep holes in which she spends time during drought.
Lives in Borneo interesting view frogs. There are membranes stretched between her fingers. With their help, she can glide in the air like a flying squirrel.
All these species belong to the family of true frogs. In addition to them, there are frogs with such exotic names as long-fingered, banana, grasping, Congolese five-lined, hairy, horned. Most of them live in Africa.
The edible frog (Rana kl. esculenta) belongs to the family True frogs, order Tailless amphibians. Coloring - the upper part is green, gray-green or green-yellow with an unclear dark spotted pattern; the belly is light, usually with dark spots. The male is up to 9 cm long, the female is up to 11 cm.
The edible frog appeared in Central Europe after the last ice age as a result of crossing the lake frog with the pond frog. The offspring of two edible frogs are not viable, so the only way for them to continue their lineage is to mate with a pond frog. Edible frogs are often found together with their parent species in their habitats - in forests, swamps, parks and gardens rich in vegetation.
The pond frog (Rana lessonae) belongs to the family True frogs, order Tailless amphibians. Coloring - the upper part is grass-green or yellow-green, sometimes blue-green, with dark spots. Body length 5-10 cm; the muzzle is sharper than that of the lake frog. The male differs from the female by the presence of paired resonators behind the corners of the mouth and dark nuptial calluses on the first toe of the forelegs; The inner calcaneal tubercle is large. It feeds on insects, small crustaceans, worms, tadpoles, frogs and young lizards.
Pond frogs overwinter in water, less often on land in earthen burrows that they dig themselves. They appear on reservoirs from the end of March. During the mating season from late April to early June, males often gather in groups in shallow water, where they make a loud chorus croak - "arr-arr-arr-kwa-kwa". Males at this time are colored yellow, their irises are also golden yellow. Females lay about 4,000 eggs in shallow water. Tadpoles appear after 7 days; development into a frog after 3-4 months.
Active day and night, pond frogs become sexually mature in most cases after the second winter. Pond frogs live on average 10 years, although not many manage to live to that age due to their enemies - snakes, water birds and predatory fish.
The lake frog (Rana ridibunda) belongs to the family True frogs, order Tailless amphibians. This is the largest domestic frog with a body length of up to 12 cm (males) or up to 17 cm (females). Coloring - olive-brownish, grass-green or dark brown above, in most cases with rather large, unevenly shaped, black or dark brown spots; belly with marble pattern; the first finger is very long; The inner calcaneal tubercle is small and flat. Habitat - from the Rhine to the Baltic in the north, the upper reaches of the Ural River in the east, to Mesopotamia and Iran in the south.

Lake frogs are always found in or near bodies of water, inhabiting a wide variety of types of bodies of water, including large, deep, fast-flowing rivers. Lake frogs are active mainly during the day, but also at night. The rhythm of daily activity changes with age and during the season, stopping when the water temperature drops to +6-9 °C. They spend the winter in the bottom mud. Calls made during the mating period by males who gather in large groups, sound like a loud, abrupt yelp. Large balls with eggs, formed by gluing the mucous membranes of the eggs, are attached to aquatic plants. During the peak of metamorphosis, large tadpoles, due to lack of nutrition, partially switch to feeding on the young of their species - they eat eggs and larvae.
The grass frog (Rana temporaria) belongs to the family True frogs, order Tailless amphibians. Body length 7-9 cm, maximum 11 cm; It is a clumsy brown frog with a short, blunt snout. The color of the upper body is from dark brown to reddish with dark stripes; the belly is white or grayish with a dark marble-like pattern. The hind limbs are shorter in relation to the body than those of a frog (if the hind leg is extended forward along the body, the ankle joint usually reaches the level of the eye).
Along with the gray toad, the most common amphibian in Europe, found in the mountains up to an altitude of 2500 m. Absent only in a number of areas of the Iberian and Apennine peninsulas, as well as on the Balkans and islands of the Mediterranean Sea. Feeds mainly on insects, snails and earthworms.
Reproduction in March-early June. As amphibians that spawn early, grass frogs often travel to their spawning grounds as early as late February, with many females carrying smaller males on their backs. Mating begins on the way to the spawning reservoirs. For spawning, animals look for small ponds, ditches and puddles. In grass frogs, large balls with eggs consist of 700-4500 eggs, which, with sufficient depth of water, sink to the bottom; older balls of eggs often float on the surface of the water.

grass frog

The sharp-faced frog (Rana arvalis) belongs to the family True frogs, order Tailless amphibians. Body length 5-6 cm. Coloring - brown or olive-gray above with dark spots and dots; belly white or yellowish; Unlike the grass frog, the front part of the head is sharp. During the mating season, males are colored light blue or bluish-violet, often with a wide light stripe on the back.
Inhabits large areas of Central, Northern and of Eastern Europe, as well as in western Asia; absent from Great Britain, Ireland, most of France, the Iberian Peninsula, Italy, Switzerland and the Balkans.
Sharp-faced frogs prefer river valleys, swamps, floodplain forests and ponds on the plains, but are also found in the mountains. They arrive at the spawning reservoir early (from early March to early May). Females, having spawned, immediately go to land, males remain in the water (up to several weeks). Males gathered for breeding in a reservoir form large clusters in shallow areas of the reservoir and make sounds reminiscent of the gurgling of water from a bottle.
A polyphonic choir sounds in the evenings tropical forest. These are thousands of tiny dart frogs serenading the rising moon. Their multi-colored bodies seem to be carved from precious stones by a skilled craftsman. Poison dart frogs spend their entire lives among branches and foliage. When the time comes to spawn, they choose plants that have accumulated in the axils of the leaves. rainwater. Most often these are various bromeliads. Above such a “pond” the frog hangs several eggs, wrapping them in a rich foam cocoon. Soon the tadpoles will break through the soft shell and fall straight into the water.
But such a body of water may not be a safe cradle at all. If there is a predator lurking at the very bottom, the newborn tadpoles will have no chance to survive. However, even without such “neighbors” there are still many dangers. Severe storm a tree can fall down - and the small “pond” with all its inhabitants will die.

pond frog