Moor frogs (Rana arvalis) are medium to large, stout brown frogs. It is characterized by a brown colouration of the back and a white colouration of the belly with small dark spots on the throat. The snout is short but relatively pointed. During the mating season, males turn blue, have stronger anterior limbs, with nuptial pads on the first finger and subcutaneous swellings resulting from lymphatic fluid retention. Adult specimens reach sexual maturity in the third year of age. They only remain in the water briefly during the breeding period, from March to April, when they are active day and night. Immediately after reproduction, adults migrate to summer habitats, even up to a kilometre away, where they feed on various terrestrial invertebrates. Most of the moor frogs hibernate on land.
Moor frogs inhabit lowland swamp meadows and floodplains along large rivers, with a dense network of temporary or permanent stagnant waters without fish, such as marshes and ponds. They avoid intensively cultivated farmlands.
Moor frogs are threatened by the loss of suitable habitats due to the logging of large and uniform areas of wetland forests, drying up standing water bodies, changing the hydrological conditions of watercourses and preventing floods of meadows, agricultural intensification and urbanization. It is extremely sensitive to changes in water quality in the environment resulting from the use of pesticides, intensive fertilization and pollution due to waste disposal. Because of the blue colouration of males during the breeding season, they are often disturbed by people at the breeding sites.