Common frogs hibernate through the winter, either at the bottom of ponds (breathing through their skin) or on land under refuges such as compost heaps (5). During the rest of the year they hunt on land on damp nights; they feed on snails, slugs, worms and a range of insects (5). In spring, males arrive at breeding areas before females, and it is thought that individuals return to their natal ponds by following scents (5). There is typically heavy competition amongst males for females, involving much croaking and wrestling. Males grab a female and remain clasped to her body for days or weeks before spawning takes place. All of the frogs in a pond tend to spawn roughly within a few days of each other. The female releases 1000 to 2000 eggs, the male then releases sperm. The eggs are coated in jelly, and are popularly known as 'frogspawn'. After 10-14 days, the tadpoles hatch, becoming free-swimming a few days later, and undergoing metamorphosis into adults 10-15 weeks after hatching. Tadpoles are vulnerable to predation by a range of aquatic creatures, including water beetles, newts and fish (5).

Vomerine teeth present. Posterior part of the tongue free and forked. Toes webbed. Omosternum and sternum ossified. Pupil of the eye horizontal. Body chunky (corpulent); snout rounded. Male with internal vocal sacs. Shin shorter than body by 1.76-2.0 times. When the shins are positioned perpendicularly to the body axis, the heels overlap. When the hind leg is stretched along the body, the tibio-tarsal articulation commonly reaches the eye. Inner metatarsal tubercle shorter than the 1st toe by 2.2-4.4 times. Dorsal coloration grey-brown, brown, olive-brown, olive, grey, yellowish or rufous. Chevron-shaped (^) dark glandular spot on the neck. Small dark spots on the dorsal and lateral surfaces. Temporal spot large. Light middorsal band usually absent. If present, this band is unclear and does not reach the middle part of the head. Flank and thigh skin often granular. Belly and hind legs white from below, yellowish or greyish with blotched-like pattern formed by brown, brownish-grey or almost black spots. Male differs from female by having nuptial pads on the first finger, paired vocal sacs and, during the breeding season, a bluish throat. During the breeding season, the male is light and greyish, whereas the female is more brownish or even rufous.

Undoubtedly Britain's most well-known amphibian, the common frog is often found in garden ponds (2). They are typically brown or greyish in colour, but some individuals may be yellow or reddish. The flanks are usually yellow, the underside white, and the upper surfaces feature variable blackish markings (5). The large hind legs feature webbed feet; they power strong jumps and an excellent swimming ability, and are covered with dark bands, which provide camouflage (5). Males tend, on average, to be slightly smaller than females, and they can be identified by whitish swellings on the inner digits of the front feet, which support dark pads during the breeding season that allow the male to effectively grasp a female (5).

It is widespread throughout most of Europe, ranging from northern Spain to the Urals (absent from southern and central Iberia, much of southern Italy [scattered Appenine populations] and the Caucasus), and eastwards to the western part of West Siberia and northern Kazakhstan through northern Greece and Bulgaria. It has a patchy distribution in the mountainous parts of the Balkans. Recorded from sea level to elevations approaching 2,700m asl (Pyrenees).

Rana temporaria is a common terrestrial frog in Great Britain, Europe and northwestern Asia. In continental Europe they are referred to as "grass frog" or "brown frog". They are resistant to cold climates and live as far north as the Arctic circle in Scandinavia, farther north than any other amphibian in the region.

(Britannica 1999-2001)

Biogeographic Regions: palearctic (Native )

The frog inhabits Europe from the Pyrenees to the Urals and West Siberia. The species inhabits almost all of western Europe except for Portugal, Central and Southern Spain and Italy, Greece (except for the most northeastern part), Southern Ukraine, and Southern European Russia. Southern margin of the range runs eastwards from Central Moldavia to the south of Ukraine (eastwards approximately along the line Odessa Province - Nikolaev Province - Kirovograd Province - Zaporozhie Province), then northeastwards approximately along the line: center of Dnepropetrovsk Province - Kharkov Province (Kharkov City, 50º00'N, 36º15'E), then in Russia: Byelgorod Province - south of Kursk Province. Then the margin runs eastwards to Voronezh Province, then northeastwards through Tambov Province to Penza and Ulyanovsk provinces, then southeastwards in Samara Province (Samara City: 53º12'N, 50º10'E) and Orenburg Province in the Southern Urals. From there, the frog penetrates Northwestern Kazakhstan (Uralsk Province, Dariinsk Settlement in the middle stretch of the Ural River: ca. 51º10'N, 51º40'E). From Orenburg Province of Russia, the margin rounds the Ural Mountains from the south and runs eastwards to northern Kazakhstan (Kustanai and Kokchetav provinces). At the southern limit of its range, the Common Frog is distributed unevenly and there is a tendency towards decline and extinction of some geographical populations and isolation of others. The northern range limit extends from the southern shore of the Barents Sea and the northern shore of the White Sea. In the Kola Peninsula, the margin corresponds to the Barents Sea coast from the Norwegian border to the area between Kharlovka and Voyatka rivers, then southwards to the northern coast of Kandalaksha Bay. Southeastwards, in Arkhangelsk Province, the margin corresponds to the coast of the White Sea, including the Kanin Peninsula. From the latter, it runs southeastwards and eastwards through Komi Republic in Russia, approximately along the line: lower Shapkina River in Ust-Tsilma District (ca. 67ºN, 53ºE) - Vorkuta City (67º29'N, 64º00'E), then to the Polar Urals, then southwards along the Ob River and the lower Irtysh River, then to Kurgan Province and Northern Kazakhstan (North-Kazakhstan Province, surroundings of Petropavlovsk City: 54º52'N, 69º09'E). It should be noted that the known localities of the Common Frog in West Siberia (east of Sverdlovsk and south of Tyumen provinces) are distributed quite sporadically, so the range margin is poorly known. At least some areas in the southeast of Sverdlovsk Province (adjacent to Tyumen Province) are inhabited by only one brown frog, the Moor Frog (Rana arvalis), and another brown frog, the Siberian Frog (Rana amurensis), is known eastwards. The eastern margin of the distribution of R. temporaria needs elucidation.

Rana temporaria inhabits lowland and mountain deciduous, coniferous and mixed forests, through which it penetrates tundra and the forest steppes. In the forest zone, it lives in quite diverse habitats: under forest cover, in glades, bushlands, dry and swampy meadows, swamps and different kinds of anthropogenic landscape (fields, gardens, parks, settlements, cities etc.). In general, in the forest zone, it inhabits quite different landscapes from dry and open areas to overmoistened, dense fir forests. In the northern and southern parts of its range, the frog tends to occur near ponds, lakes and rivers, spending more time in water, a habit typical for this species also in the forest zone in periods of droughts. At the northern limit of its distribution, R. temporaria lives in the forest and true tundras, usually on the shores of permanent lakes. At the southern limit of its range, the frog lives in insular forests in the forest and true steppes, riverside bushlands and plavni (dense riparian vegetation in southern arid regions). In these areas, the species lives only in very moist sites, particularly near the outcrops of ground waters, and behaves as a more hygrophilous species than sympatric R. arvalis. Reproduction and early development occur in the shallow (5-50 cm) waters of lakes, ponds, swamps, ditches, river- and stream pools and puddles with stagnant or semi-flowing water. Aquatic habitats are more diverse in the centre of the species range than on its periphery.

Found throughout Britain and Ireland (2). Elsewhere, the common frog occurs in most of Europe, with the exception of Portugal, most of Spain, Italy and Greece (4).

Rana temporaria is a small animal that has a squat body and no tail. They have a wide, flat head connected to a short, solid body. The lower segments of the frogs backbone are fused, forming a stiff rod called the urostyle. Their urostyle and their pelvic bones help provide firmness and strength to the rear of the body, which is where the muscles used for jumping attach to the skeleton. Their powerful legs are not only used for jumping but for swimming as well.

They have a brown-black triangular area around their eardrum, and brown shades covering the rest of their body, though there is a lot of variation in color, with gray, olive, even yellow or pink hues as well. Females are typically yellower and may have patches of red on their sides. Males develop blue patches on their back and throat during breeding season. For the most part females tend to be larger than males. The common frog is approximately 7.5-8 cm long. They lack vocal sacs and therefore can only be heard approximately 50 meters away.

(Mattison 1982; Britannica 1999-2001)

Average mass: 22.7 g.

Habitat and Ecology

Systems

• Terrestrial
• Freshwater

Rana temporaria can be found in just about any damp habitat within its range, though they are more common in cooler upland forests and wet meadows. They are the most common frog in mountain lakes.

Terrestrial Biomes: taiga ; forest ; mountains

Aquatic Biomes: lakes and ponds; rivers and streams

Found in a wide range of habitats, and breeds in puddles, ditches, ponds and large lakes as well as urban and rural garden ponds (5). They have even been recorded breeding in running water (5).

Rana temporaria eats insects, their larvae, wood lice, spiders, snails and worms. They are able to detect worms by smell. Eating habits are greatly influenced by the time of year.

(Duellman and Trueb 1986; Mattison 1993)

In Great Britain and/or Ireland:
Animal / dung saprobe
Basidiobolus ranarum is saprobic in/on dung or excretions of dung of Rana temporaria

Range lifespan

Status: wild: 14 (high) years.

Maximum longevity: 27 years Observations: An age-related decline in the immune system has been described in the common frog (Plytycz et al. 1995). In the wild, these animals may live up to 14 years (Smirina 1994).

Mating is by means of external fertilization and takes place in water. The male climbs on the back of the female and grasps her body with his forelegs. He releases his sperm as she lays her eggs. Once the male mounts a female he will not release her until egg-laying is complete. The eggs are in gelatinous envelopes (about 400 eggs) and are laid in thick groupings. It takes approximately 30-40 days for their eggs to hatch. A relatively cold spring initiates mating behavior and maturation of eggs. During metamorphosis the tadpole grows legs-the hind legs are the first to grow. Its tail is absorbed into its body and it loses its gills and grows lungs. The structure of the digestive system, heart and skeleton change as well.

Rana temporaria breeds in warmer lowlands in February & March and in the north and at high altitudes as late as June. The breeding period is much shorter in this species than in others; in 3 nights these frogs will lay hundreds of eggs.

Average age at sexual or reproductive maturity (male)

Sex: male: 1095 days.

Average age at sexual or reproductive maturity (female)

Sex: female: 1095 days.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Species: 1
Species With Barcodes: 1

This common species is currently in no danger of extinction, but local populations can be very unstable. Disturbance of breeding ponds, unusually hard freezes, and pollution by herbicides are all known to wipe out the species in a region.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

Protected in Britain under Schedule 5 of the Wildlife and Countryside Act (1981), with respect to sale only (3). Listed under Annex III of the Bern Convention (4).

Population

Population Trend

In the center of the forest zone, the Common Frog is usually the most common amphibian. For example, in mixed forests in the centre of European Russia, abundance varies depending on habitat and activity period approximately within the range of 1-250 specimens per 1000 m². Rana temporaria is common also in agricultural areas and even settlements and cities. In the forests of the center of European Russia, it usually prefers denser parts of forest habitats than the sympatric Moor Frog, and is rarer than the latter in the south, whereas the proportion gradually changes to the north and northwest in favor of R. temporaria. The proportion of the two species varies also by years and in some areas the dominance of one or another species alternates. Density-dependent regulation is important in overcrowded tadpole groups, where several hundred individuals per liter sometimes occur, as well as in the dense groups of recently metamorphosed froglets. However, habitat peculiarities and fluctuations in weather and climate appear to be more important in terms of the overall population dynamics. The Common Frog in the European region is probably a less thermophilous species than the sympatric Moor Frog. It frequently occurs in cooler and wetter microhabitats. The frog usually hibernates in water: rivers, channels, ditches, springs, streams and lakes, primarily with a current. In underwater hibernacula, the Common Frog occurs in groups of many, sometimes few thousand individuals. Hibernation occurs from August - November to February - early June, depending on latitude and altitude. Reproduction occurs from March - late June, but generally in April over the main part of its distribution. Amplexus is pectoral (axillary), and it sometimes occurs on land on the way to the breeding pond. The spawn in deposited usually in a large clump containing 670-4500 eggs. Many, sometimes hundreds and more, clumps form large aggregations. The advantages of embryonic development in large aggregations is that it minimizes temperature fluctuations and that it decreases predation potential, especially with regards to small predators, for example, invertebrates and newts, which are less successful in penetrating large aggregations than single clutches. In such masses, the temperature is a little higher than in the surrounding water. These factors lead to an increase in embryonic survival and probably accelerate development. On the other hand, the rate of embryonic development is slower and mortality is higher in the lower parts of the aggregation than in the upper parts because of hypoxia. In this respect, group spawning in shallow sites will be more advantageous than in deep sites. Metamorphosis is completed usually in June - August. Larvae tend to concentrate into large schools in shallow water where their density sometimes reaches 100 individuals per liter. These schools may cover several hundred square meters, and the temperature there may be a little different from that in surrounding water. Crowding effect is typical for such tadpole aggregations, and the sizes of metamorphosed juveniles are variable. Larger juveniles usually metamorphosed first. They have higher survival rates during their first overwintering, which emphasize an advantage of early metamorphosis. Sexual maturity is attained no later than the 3rd year of life; the life span reaches 6 - 8 years, in the Polar Urals even 17 years.

The tadpoles consume mainly detritus, algae and higher plants. Animal food is consumed in smaller amounts. Plant and animal food diversity increase during the ontogenesis. At metamorphosis, feeding ceases for a short time after the appearance of the tadpole's forelegs. Recently metamorphosed juveniles primarily eat microarthropods: Acarina, Collembola, small larvae of Diptera. The food spectrum increases in postmetamorphic development. Adults eat mostly terrestrial prey, including Lumbricidae, Gastropoda, Aranei, Insecta etc. Aquatic prey, mainly insects and molluscs, are eaten in the largest amounts in the northern parts of the frog's distribution. From the other hand, R. temporaria, as the another brown frog, R. arvalis, compose an important food component of many vertebrate animals. It is supposed that the dynamics of some mustelids depend on the population number and dynamics of these brown frogs. The helminth composition in R. temporaria is quite similar to that of the related frog, R. arvalis.

Major Threats

The species is generally neither declining, nor threatened. However, isolated peripheral populations may be vulnerable from human influences and deserve special attention or protection. Only in some areas highly transformed by people (destruction of breeding ponds and adjacent terrestrial habitats, especially during urbanization, recreation and the overpasturage of cattle) the populations are declining. In southern regions, the species is rare, but at its northern distribution in Europe it is common. However, in some West European countries (Great Britain, parts of Germany, Switzerland, etc.), the frog declines drastically due to industrial destruction and pollution of habitats (especially ponds and swamps).

Phillimore et al. (2010) suggests that projected increases in temperature for Britain (by 2050-2070) may be more than the Rana temporaria can handle, due to local adaptation. Their models predict that first spawning date for populations in southeast Britain will need to advance by about 21-39 days, but genetically influenced plasticity in spawning date may only allow an advance of 5-9 days. Gene flow northward from more southern populations already adapted to higher temperatures could help, but is unlikely due to the barriers of the English Channel and high urbanization.

For several decades up until the 1970s, this frog suffered a serious decline in Britain. Since the increase in popularity of garden ponds, however, it has experienced a welcome recovery. It is not currently threatened, but populations are vulnerable to the destruction and pollution of water bodies (4). Inbreeding in garden ponds caused by isolation is thought to be a serious problem in some areas, leading to reduced immunity and an increase in disease (5).

Conservation Actions

It is illegal to sell common frogs under the Wildlife and Countryside Act, 1981 (2).

Rana temporaria are of great importance to humans. They consume insects, which helps control populations of mosquito's and crop-damaging insects. Frogs are also important when it comes to teaching and scientific research. Adult frogs are used to teach students about the anatomy and physiology of vertebrates and help scientist learn about embryonic development. Ecologists monitor frog populations as they reflect the health of the ecosystem as a whole. In addition, frog legs are a delicacy in many parts of Europe. (Mattison 1987) 

Although many kinds of anthropogenic influences (habitat destruction and pollution, recreation, etc.) negatively affect many populations of the Common Frog, it is a species well-adaptable to life in anthropogenic conditions. Some urban populations of this species are fairly large and safe, if suitable habitats are available. Even a high level of exploitation of the frog population for purposes of medicine and education in some sites does not destroy them. Some forms of human activity lead to an increase in the frog's number and their dispersal. For example, the construction of forest rides with numerous artificial holes filled with water. Many frogs are caught for the purposes of education, medicine and science. Along with the Marsh Frog (Rana ridibunda), the Common Frog is the main subject for such collecting. The amount of these two frog species caught in the 1970s - 1980s in the former USSR measured by several tons annually. However, no population declines resulted from this.