Vomerine teeth present. Posterior part of the tongue free and forked. Toes webbed. Omosternum and sternum ossified. Pupil of the eye horizontal. Snout more or less terminating in a point. Male with internal guttural vocal sacs. Shin (knee to ankle) shorter than body by 1.9-2.6 times. When the shins are positioned perpendicularly to the body axis, the heels contact or overlap. When the hind leg is stretched along the body, the tibio-tarsal articulation usually reaches the eye, nostril, tip of snout or even slightly exceeds it. Inner metatarsal tubercle high, shorter than the first toe by 1.1-2.3 times. Flank and thigh skin smooth. 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
Northern margin of the range extends from the Southwestern Norway, Central Sweden and Finland to Northwestern Russia. There, the margin runs from Murmansk Province, then approximately along the line: Arkhangelsk Province (Pinezhskii Nature Reserve - south of the Kanin Peninsula - Nenets Autonomous County) - Komi Republic (Vorkuta City: 67º29'N, 64º00'E) - Tyumen Province (Yamal-Nenets Autonomous County, Kharvuta Settlement on the Khadyta-Yakha River) - Krasnoyarsk Region (Taimyr Autonomous County). Then the margin runs south-southeastwards from the Enisei River to the Chuna River in Krasnoyarsk Region and Irkutsk Province (Boguchan District) and to Irkutsk City (52º19'N, 104º18'E). The frog inhabits the valleys of the Lena River and its tributaries from Irkutsk City northeastwards to Sanyyakhtakh Settlement in Yakutia (ca. 60º40'N, 124ºE). The frog was recorded also in Olekminskii Nature Reserve (58º45'N, 122º20'E). From the valley of the Lena River in Irkutsk Province (Kirensk Settlement: 57º45'N, 108º04'E), the margin runs southwards on the northern shore of Lake Baikal near the Baikalskii Ridge. To the south of Baikal Lake, in Buryatia, the frog is distributed from the Irkut River northeastwards along the southern shore of the Baikal to Barguzinskii Nature Reserve (54º23'N, 109º05'E).The southern margin of the range runs approximately from the Southern France and Germany, Northern Yugoslavia, Central Bulgaria, then by the Southern Ukraine approximately along the line: Odessa Province (Kiliya District) - Nikolaev Province - Kherson City - Zaporozhie Province - Donetsk Province. Then the margin runs in Russia eastwards to Rostov Province and northeastwards to the south of Volgograd Province. Then it runs eastwards in Kazakhstan approximately along the line: Uralsk City (51º13'N, 51º22'E) - Aktyubinsk City - Turgai Province - Tselinograd Province - Karaganda Province - Semipalatinsk City area (50º27'N, 80o14'E). Then the margin turns southwards to Ayaguz Town (47º58'N, 80º26'E) and Taldy-Kurgan Province (to the west of Alakol Lake, Uch-Aral Settlement: ca. 46º20'N, 80º40'E), then to Altai Mountains in the north of China and Mongolia.
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.
Habitat and Ecology
Life History and Behavior
Lifespan, longevity, and ageing
IUCN Red List Assessment
Red List Category
Red List Criteria
- 2004Least Concern
Life History, Abundance, Activity, and Special Behaviors
Rana arvalis is one of the most abundant amphibians in the Central and Eastern Europe, as well as West Siberia. There, its population density reaches several hundred individuals per hectare. Local density may be higher, such as in breeding ponds where 15-20 individuals per 1 m2 can be found. In the forests of the center of European Russia, it usually prefers more open habitats than the sympatric Common Frog, and is rarer than the latter in the north, whereas the proportion gradually changes to the south and southeast in favor of R. arvalis,> and at the south of the zone of sympatry it significantly outnumbers R. temporaria. The proportion of the two species varies also by year, 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 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 fastly developing tadpoles often complete their transformation, while slowly developing specimens 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.
Life History, Abundance, Activity, and Special Behaviors
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) have the populations declined.
Relevance to Humans and Ecosystems
Relation to Humans
In addition to the above mentioned anthropogenic factors of the species local declines, industrial pollution also negatively affects populations, including those living in cities. It leads to an increase of frequency of morphological abnormalities and disturbances in embryonic and larval development. Nevertheless, R. arvalis is a species easily adaptable to life in anthropogenic conditions. Some urban populations of this species are fairly large and safe, if suitable habitats are available. 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.
The family the moor frog belongs to, Ranidae, is a broad group containing 605 species. The family is like a “catch-all” for ranoid frogs that do not belong to any other families. Since this is the case, the characteristics that define them are more general, and the frogs are found all throughout the world, on every continent but Antarctica.
The moor frog’s genus, Rana, is a little more specific. Frogs of this genus are found in Europe, Asia, South America, and North America. The moor frog is not found in either of the Americas, unlike the foothill yellow-legged frog, Cascades frog, and Columbia spotted frog, which are all found in North America.
The moor frog’s scientific name, Rana arvalis means "frog of the fields". It is also called the Altai brown frog because frogs from the Altai Mountains in Asia have been included in the R. arvalis species. The Altai frogs have some different characteristics such as shorter shins, but currently there is no official distinction and all frogs are placed under Rana arvalis. The taxonomy may be more defined in the future.
This is a small frog, characterized by an unspotted belly, a large, dark ear spot, and — often, not always — a pale stripe down the center of the back. They are generally described as a reddish-brown, but can also be yellow, gray, or light olive. Their bellies are white or yellow and they have a "bandit-like" black stripe going from their nose to their ears. They vary from 5.5 to 6.0 cm long, but can reach up to 7.0 cm in length, and their heads are more tapered than those of the Common frog (Rana temporaria). The skin on their flanks and thighs is smooth, and the posterior part of their tongues is forked and free. They have horizontal pupils, their feet are partially webbed, and their back legs are shorter than those of other species of frogs. The males are different from the females because of the nuptial pads on their first fingers and their paired guttural vocal sacs.
The frogs can be found inhabiting an area stretching from the lowlands of Central and Southern Europe to Siberia, in Austria, Belarus, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Hungary, Italy, Latvia, Lithuania, Moldova, Netherlands, Norway, Poland, Romania, Russian Federation, Slovakia, Slovenia, Sweden, Switzerland, and Ukraine. However, they are believed to be extinct in Switzerland and maybe Siberia, as well. The records of frogs being in Siberia at all possibly were in error. Alsace, France, constitutes the western boundary of their territory.
The types of land they can inhabit are greatly varied. They live in tundra, forest tundra, forest, forest steppe, and steppe, forest edges and glades, semideserts, swamps, meadows, fields, bush lands, and gardens. They prefer areas untouched by humans, such as damp meadows and bogs, but they still may be able to live in agricultural and urban areas.
Moor frogs will hibernate sometime between September and June, depending on the latitude of the location. Frogs in southwestern, plains areas will disappear later (around November or December) and return earlier (February). Frogs in cold, polar areas, though, will disappear sooner (in September) and return later (in June).
The mating season takes place between March and June right after the end of hibernation. Males form breeding choruses, and their songs sound similar to those of the agile frog, (Rana dalmatina). Their calls can "sound like air escaping from a submerged empty bottle: 'waug.…waug….waug'. Males can also develop bright-blue coloration for a few days during the season.
The spawning happens very quickly and is completed in three to 28 days. The spawn of each frog is laid in one or two clusters of 500-3000 eggs in warm, shallow waters like in ponds.
Metamorphosis happens between June and October. Larvae are about 45 mm long and colored dark with small metallic dots. When they become tadpoles, they eat algae and small invertebrates. The adult frogs' feeding is halted during the breeding season, but their diets consist of insects and various invertebrates.
When moor frogs on land sense a threat, they will make a large jump and bury themselves in soil or grass.
This species faces few major threats and is on the IUCN's Lowest Concern list. There are problems, though, with destruction and pollution of its habitat and breeding grounds through urbanization, etc., where people overwhelm their environments. Droughts and predation can also cause problems, but overall it quite adaptable and its population trend is considered stable.
Extensive scientific experiments have been performed on moor frogs in an attempt to understand them better. This species is known to have a limited decline in population, but increased acidity levels in breeding areas might be a problem. Studies have shown, when moor frogs are exposed to acidity, they are able to adapt to it and their populations survive.
- Sergius Kuzmin, David Tarkhnishvili, Vladimir Ishchenko, Boris Tuniyev, Trevor Beebee, Brandon Anthony, Benedikt Schmidt, Agnieszka Ogrodowczyk, Maria Ogielska, Wiesiek Babik, Milan Vogrin, Jon Loman, Dan Cogalniceanu, Tibor Kovács, István Kiss (2009). "Rana arvalis". IUCN Red List of Threatened Species. Version 2012.2. International Union for Conservation of Nature. Retrieved 20 November 2012.
- Eldredge. "Life on Earth." 2002
- http://www.waza.org/virtualzoo /factsheet.php?id=403-016-040-012&view=Amphibia
- Andren, Claes, Marlene Marden, and Goran Nilson. “Tolerance to Low pH in a Population of Moor Frogs, Rana arvalis, from an Acid and a Neutral Environment: A Possible Case of Rapid Evolutionary Response to Acidification.” Oikos. 56 (1989): 215-223
- Merila, Juha. “Local adaptation and amphibian pH tolerance.” Ecological Genetics Research Unit. 18 Sept. 2008. 28 Mar. 2009<http://www.helsinki.fi/biosci/egru/merila/e/ project3.html>.
- Räsänen, Katja, Anssi Laurila, and Juha Merilä. “Geographic Variation in Acid Stress Tolerance of the Moor Frog, Rana arvalis. I. Local Adaptation.” Evolution. 57 (2003): 352-362
- Tarkhnishvili, David, et al. “Rana arvalis.” IUNC Red List of Threatened Species. 2008. 25 Mar. 2009 < http://www.iucnredlist.org/apps/redlist/details/full/58548/0 >.
- Kuzmin, Sergius L. “Rana arvalis.” AmphibiaWeb. 10 Nov. 1999. 26 Mar. 2009 < http://
- Althaus, Thomas. “Moor Frog.” WAZA. 2007. 26 Mar. 2009. < http://www.waza.org/virtualzoo
- "Google Books". Concise Encyclopedia of Biology. Retrieved 2006-03-27.
- Some parts of this article were translated from the article Grenouille des champs on the French language Wikipedia.