The moor frog (Rana arvalis) is a reddish-brown, yellow, grey or olive frog in the family Ranidae, found in Europe and Asia. Usually 5.5 to 6.0 centimetres (2.2 to 2.4 in) long, it has horizontal pupils, partly webbed feet and, in males, nuptial pads and paired vocal sacs. The species inhabits varied wetlands, meadows, forests, steppes, bogs and farmland, from lowlands to high elevations, and tolerates acidic breeding pools. It feeds opportunistically on small invertebrates, with prey size broadly matching frog size. Breeding follows hibernation; males form choruses and may turn bright blue for a few days during mating. Although listed as a least-concern species, it is threatened in some areas by habitat loss, drainage, pollution, acidification and fragmentation. This moor frog was photographed in Uckermark Lakes Nature Park, Germany.

Photograph credit: Charles J. Sharp