Rana arvalis Nilsson, 1842
© 2016 Dr. Joachim Nerz (1 of 136)
Dorsal coloration grey, light-olive, brown, yellowish or rufous. Chevron-shaped (^) dark glandular spot on the neck. Dark spots of 1-3 mm on dorsal and lateral surfaces vary considerably in number, arrangement and size. Temporal spot large. Light middorsal band with regular edges frequently present, often reaches the middle or the tip of the snout. Belly white or yellowish without pattern or with pallid-brownish or greyish spots on the throat and chest.
Male differs from female by having nuptial pads on the first finger, paired guttural vocal sac and, during the breeding season, light-blue coloration of the body (the female is brown or rufous). Subspecific differentiation needs further study. The species belongs to the "brown frog" group.
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Austria, Belarus, Belgium, China, Czech Republic, Denmark, Estonia, Finland, France, Germany, Hungary, Italy, Kazakhstan, Latvia, Lithuania, Moldova, Republic of, Netherlands, Norway, Poland, Romania, Russian Federation, Slovakia, Slovenia, Sweden, Switzerland, Ukraine
The Moor Frog inhabits the zones of tundra, forest tundra, forest, forest steppe, and steppe. In Europe, the frog generally inhabits drier and more open sites than the Common Frog (Rana temporaria), including forest edges and glades, swamps, meadows, fields, bushlands gardens, etc. In Siberia, the species lives mainly in open swamps. The frog penetrates tundra and steppe in association with arboreal vegetation, primarily along intrazonal landscapes of river valleys. At the southern and northern limits of its range, in tundra, forest, and true steppes, the species lives near water bodies: rivers, lakes etc. There the populations of R. arvalis seem to be isolated. Spawning and early development occurs in stagnant waters, including lakes, ponds, swamps, puddles and ditches, which are from several meters to some hectares in area and from few centimeters to two meters in depth.
Life History, Abundance, Activity, and Special Behaviors
The Moor Frog in the European region is probably a more thermophilous species than the sympatric Common Frog. It frequently occurs in warmer and drier microhabitats. Hibernation extends from September - November to February - June, in dependence on latitude. The earliest appearance (February) and latest disappearance (late November - December) takes place in the plain areas at the southwest of the species distribution, whereas the latest appearance (June) and earliest disappearance (September) is in the Polar Urals. Reproduction occurs from March - June, usually some days after the end of hibernation. Males form breeding choruses. Amplexus is pectoral (axial). The total duration of the breeding season within a pond is 3-28 days. Eggs are deposited in shallow, well-warmed sites, during both day and night. However, spawning by the Moor Frog peaks later than that of the Common Frog; it prefers more open and shallow wetlands for reproduction. The clutch contains 500-3000 eggs deposited usually in one, rarely in two clumps.
Metamorphosis occurs from the beginning of June to October in different regions. In general, the duration of development before metamorphosis shortens in the north and the south of the distribution. Formation of dense schools of tadpoles, where density-dependent regulation of development takes place, is typical. The density does not influence larval survival rate directly but influences the probability of successful metamorphosis because fast developing tadpoles often complete their transformation, while slowly developing individuals die in drying wetlands. "Delayed" larvae metamorphosed into froglets at significantly smaller body sizes and possessed less energy reserves. This may be evidence of lower viability. However, in good living conditions, their compensatory growth may enable them to reach the size of specimens from early clutches. However, this compensatory growth takes place relatively seldom, and more often the growth does not depend on individual size after metamorphosis. Sexual maturity is attained in the 2nd-5th year of life. On average, females mature later and have a longer life span than males. The maximum life span recorded for this species is 11 years old.
Moor Frog tadpoles eat Chlorophyta, Cladocera, and other algae, higher plants, detritus, as well as small amounts of invertebrates. Recently metamorphosed froglets forage on Acarina, Collembola and other microarthropods. Adults consume mainly terrestrial prey, aquatic invertebrates (slugs, diving beetles etc.) are consumed in smaller proportions and, as a rule, irregularly. Feeding ceases during the reproductive season.
Trends and Threats
Relation to Humans
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Originally submitted by: Sergius L. Kuzmin (first posted 1999-11-10)
Edited by: Meredith J. Mahoney, Michelle S. Koo (2022-08-16)
Species Account Citation: AmphibiaWeb 2022 Rana arvalis: Moor Frog <https://amphibiaweb.org/species/4983> University of California, Berkeley, CA, USA. Accessed Dec 1, 2023.
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Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 1 Dec 2023.
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