Sharp-faced Frog (Rana Arvalis)

The sharp-faced frog, or marsh frog (Rana arvalis), is the most common amphibian species. It lives in a wide variety of areas, as well as in all the main green areas of the city, gardens, parks. The general tone of the color depends on the weather, for example, on a sunny day, frogs brighten significantly. Frogs are most active in the evening, but they can often be found during the day. It feeds on land on various invertebrates. This is the only species of tailless amphibians found in the tundra.

Area

The most common amphibian species everywhere. Inhabits various zones: tundra, forest-tundra, forest, forest-steppe and steppe; as well as in all the main green areas of the city, gardens, parks.

Appearance

The sharp-faced frog belongs to the group of brown frogs. The muzzle is slightly pointed. The shins are 1.9-2.6 times shorter than the body. The inner calcaneal tubercle is high, 1.1-2.3 times shorter than the first toe of the hind leg, laterally compressed. The temporal spot is large, extending from the eye through the eardrum almost to the shoulder, gradually narrowing. The dorsomedial stripe that reaches the middle or end of the muzzle is often found. The male differs from the female by the presence of mating calluses on the 1st toe of the front foot, a paired throat resonator and, during mating season, a light blue body color (the female is brown or reddish brown). The skin on the sides and thighs is smooth. On the back and sides of the frog there are dark spots of 1-3 mm, which vary greatly in number, location and size.

Color

The general tone of the color depends on the weather, for example, on a sunny day, frogs brighten significantly. The color is gray, light olive, yellowish, brown or reddish brown. The belly of a sharp-faced frog is white or yellowish without a pattern, or with pale, brownish or grayish spots on the throat and chest.

The size

Adult frogs grow up to 36-80 mm.

Related article Grass Frog (Rana temporaria)

Habitat

At the northern borders of the range, the sharp-faced frog keeps in water bodies or in the coastal zone. It is active at dusk, at night and during the day (during rain). With decreasing temperature, activity decreases. Dry air is destructive for frogs.

Enemies

Enemies include vipers, snakes, marsh frogs, storks, little bitters, river gulls, lesser spotted eagles, crows, badgers, minks, ferrets, foxes, weasels, and hedgehogs.

Sharp-faced frog, male in breeding plumage

Nutrition / food

The sharp-faced frog hunts only for mobile insects, instantly grabbing prey with a long sticky tongue. The diet depends on the habitat: beetles, spiders, filly, bedbugs, caterpillars, mosquitoes, ants, The forage areas of different frogs living in the neighborhood overlap. The size of the feeding area and the adherence of frogs to it is determined by its feeding capacity. If food becomes scarce or moisture conditions change, the marsh frog begins to migrate to other places. Movements are made gradually at a speed of 3-20 m per day, while not only feeding areas, but also biotopes can change. Such movements can be made for several weeks, and for two or more seasons.

Behavior

The marsh frog lives most of its life on land, breeding in water in early spring. Going on land, he chooses a suitable, usually 200-300 sq.m. area, where he hunts and which protects from relatives. Lives on this site until winter. It goes hunting in the evening and actively feeds between 20-22 hours. After midnight, activity begins to decline, and from 4:00 to 18:00, activity is low. In inactive time, it hides at the bottom of reservoirs, in summer it hides in more humid places (under fallen trees, in stumps, etc.) The sharp-faced frog leaves for wintering from the beginning of September to the end of October. The duration of hibernation is 165-170 days. Young frogs hibernate later than adults. It hibernates on land in groups: in pits covered with leaves, in heaps of foliage and brushwood, in holes of rodents, etc.

Reproduction

Reproduction and early development take place in stagnant bodies of water (lakes, ponds, swamps, puddles, ditches). It comes to spawning reservoirs from a distance of up to 1 km in 3-4 days. The sharp-faced frog, having come to the reservoir without delay, begins to reproduce. Males gathered for breeding in a reservoir form large clusters. For a long time, males spend in reservoirs, trapping females that have not yet swept away their eggs. Individual males can remain in the reservoir for up to 20-25 days. Females not only come into the reservoir later than males, but, having swept away the eggs, immediately leave it. The water temperature at which the spawning begins is 12.0-14.8 ° C. Eggs are laid both during the day and at night, in shallow, well-warmed places with a depth of 5-30 cm. Females lay eggs in the form of lumps near the shore. Caviar lies at the bottom for about a day,then pops up. In one place, a huge amount of eggs is often formed, laid by many females.

Season / period of breeding

The breeding season begins in March-June, usually a few days after the end of wintering. One female lays 500-2700 eggs (depending on age). The diameter of an egg with shells is 7-8 mm, without shells 1.2-2 mm.

Sharp-faced frog, male and female

Puberty

Maturation occurs when the size is: in females - 42.5 mm, in males - 43.4 mm.

Courtship ritual

Axillary amplexus. Mixed pairs of Rana arvalis and Rana temporaria are not uncommon.

Incubation

Caviar of sharp-faced frogs develops in 5-10 days.

Development

The tadpoles are 5-8 mm long, 35-48 mm before metamorphosis. In the newly hatched larva, body parts are barely marked. The head is separated from the body by a slight interception, and the posterior end of the embryo is extended into a long tail. The tail is surrounded by a wide fin running along the back of the larva. The tadpoles are black. In the area of ​​the mouth in a magnifying glass, they can see three rows of keratinized teeth. External gills of considerable length develop shortly after hatching. In the first half of the larval development, before the appearance of the rudiments of the extremities, when the processes of formation of various organs are intense, the tadpoles of the sharp-faced frog increase by 0.4 mm per day. All larval development takes 60-65 days on average, but in exceptional cases it can take up to 120 days. Duration of metamorphosis is 4 days. Tadpoles eat cladoceransdiatoms and other algae, higher plants, detritus and in a small number of aquatic invertebrates. They feed around the clock, but they form food accumulations only during the day. During the period of metamorphosis, food stops for a short time and is resumed even before the end of the metarmophical climax. Recently metamorphosed underyearlings prey on ticks, springtails, and other small arthropods.