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.
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Austria, Belarus, Belgium, Bulgaria, Czech Republic, Denmark, Estonia, Finland, France, Germany, Hungary, Ireland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Montenegro, Netherlands, Norway, Poland, Romania, Russian Federation, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Ukraine, United Kingdom
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.
Life History, Abundance, Activity, and Special Behaviors
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.
Trends and 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.
Relation to Humans
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.
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Written by Sergius L. Kuzmin (ipe51 AT yahoo.com), Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow
First submitted 1999-11-10
Edited by Meredith J. Mahoney, Kellie Whittaker (2010-05-31)
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