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	Conservation Status (definitions)
IUCN (Red List) Status	Least Concern (LC) See IUCN account.
CITES	No CITES Listing
Other International Status	Not Threatened
National Status	None
Regional Status	Bern Convention (Annex 3)

Description
This hybrid form displays a morphology intermediate between its parental species, the Pool Frog (Rana lessonae) and the Marsh Frog (R. ridibunda). This trait is revealed, in particular, in the values of some characters having identification value. When the shins are positioned perpendicularly to the body axis, the heels contact. Inner metatarsal tubercle 1.73-2.89 times shorter than the first toe. Dorsal coloration greyish-green, olive-green or green with dark spots which vary in size and number. Light middorsal line from snout to cloaca usually present. No temporal spot. Belly light, usually with dark spots. Male vocal sacs positioned behind the mouth angles and are grey.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Albania, Austria, Belarus, Belgium, Bosnia and Herzegovina, Bulgaria, Croatia, Czech Republic, Denmark, Estonia, France, Germany, Hungary, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Moldova, Republic of, Montenegro, Netherlands, Poland, Romania, Russian Federation, Serbia, Slovakia, Slovenia, Sweden, Switzerland, Ukraine. Introduced: Spain, United Kingdom.

View distribution map using BerkeleyMapper.

The range of this form is almost identical to that of R. lessonae. It should be observed, however, that in the eastern part of the distribution of R. lessonae (in the Volga-Kama region in Central Russia), the latter species is sympatric with R. ridibunda at many sites but R. esculenta is very rare. At the same time, R. esculenta occurs in Estonia where one of the parental species, R. ridibunda, is considered to be extinct. It should be observed that it is not easy to distinguish the hybrid form and its parental species for inexperienced observers, so some records of R. esculenta require further verification.

In general, R. esculenta is very similar to R. lessonae in ecology but it also occurs in some habitats of R. ridibunda. As a rule, it lives in habitats which are intermediate in their parameters between the two parental species: floodland lakes, overgrown ponds, river pools, channels, ditches etc. However, R. esculenta avoids very large pools with flowing water and does not enter dense forests.

Life History, Abundance, Activity, and Special Behaviors
Rana esculenta appears to be relatively rare in the south-eastern and eastern parts of its range. Hibernation occurs from September-October to March-May. The mode of hibernation resembles that in coexisting parental species: in water (when coexisting with R. ridibunda) or on land (with R. lessonae). Breeding calls in R. esculenta are more similar to those in R. lessonae than R. ridibunda. The same concerns some other behavioral and ecological traits.

Relation to Humans
The species occurs not only in natural but also in anthropogenically altered habitats.

Comments
Rana esculenta is the hybrid of R. ridibundaand R. lessonae. Together with diploid individuals, hybrid populations may also contain triploids. Great variability in the population systems of these three forms exists within the range, where the hybrid (or either parental) form may coexist or not coexist with the both (or any) other forms. Genetic, ecological and behavioral studies in these frogs are in progress.

References
 

Bannikov, A. G., Darevsky, I. S. and Rustamov, A. K. (1971). Zemnovodnye i Presmykayushchienya SSSR [Amphibians and Reptiles of the USSR]. Izdatelistvo Misl, Moscow.  

Bannikov, A. G., Darevsky, I. S., Ishchenko, V. G., Rustamov, A. K., and Szczerbak, N. N. (1977). Opredelitel Zemnovodnykh i Presmykayushchikhsya Fauny SSSR [Guide to Amphibians and Reptiles of the USSR Fauna]. Prosveshchenie, Moscow.  

Gasc, J.-P. (1997). Atlas of Amphibians and Reptiles in Europe. Societas Europaea Herpetologica, Bonn, Germany.  

Gunther, R. (1990). Die Wasserfrosche Europas. A. Ziemsen, Wittenberg-Lutherstadt.  

Kuzmin, S. L. (1995). Die Amphibien Russlands und angrenzender Gebiete. Westarp Wissenschaften, Magdeburg.  

Kuzmin, S. L. (1999). The Amphibians of the Former Soviet Union. Pensoft, Sofia-Moscow.  

Nikolsky, A. M (1936). Fauna of Russia and Adjacent Countries: Amphibians (English translation of Nikolsky, 1918, Faune de la Russie et des Pays limitrophes. Amphibiens. Académie Russe des Sciences, Petrograd, USSR). Israel Program for Scientific Translations, Jerusalem.  

Nikolsky, A. M. (1906). Herpetologia Rossica. Mémoires de l'Académie Impériale des Sciences de St.-Pétersbourg, Série 8, Phys.-Math, Vol. 17, Sofia, Moscow.  

Nöllert, A. and Nöllert, C. (1992). Die Amphibien Europas. Franckh-Kosmos Verlags-GmbH and Company, Stuttgart.  

Szczerbak, N. N. and Szczerban, M. I. (1980). Zemnovodnye i Presmykayushchiesya Ukrainskikh Karpat [Amphibians and Reptiles of Ukrainian Carpathians]. Naukova Dumka, Kiev.  

Terent'ev, P. V. and Chernov, S. A (1965). Key to Amphibians and Reptiles [of the USSR]. Israel Program for Scientific Translations, Jerusalem.

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