The river frog (Lithobates heckscheri) is a species of aquatic frog in the family Ranidae. It is endemic to the southeastern United States. Its natural habitats are temperate rivers, swamps, freshwater lakes and freshwater marshes. It is threatened by habitat loss. Taxonomy Historically, the river frog has been known as Rana heckscheri but was placed in the genus Lithobates by Frost et al., 2006, this being a separate genus of ranid frogs that included most of the North American frogs traditionally included in the genus Rana. This change has proved controversial, and some authorities treat Lithobates as a subgenus of Rana, with the river frog's scientific name being written Rana (Lithobates) heckscheri. Description The river frog is a very large species with adults commonly between in length. The skin is rough and wrinkled but there are no dorso-lateral ridges as there are in the green frog (Lithobates clamitans). The back is some shade of dark green or blackish-green and the belly is dark grey, or blackish with pale wavy lines and specks. A distinctive characteristic is white spots on the lips, particularly on the lower lip, and this helps to distinguish this species from bullfrogs (Rana catesbeiana) and pig frogs (Rana grylio). Another distinguishing feature is a pale band outlining the groin. Males have a yellowish throat and their tympani (eardrums) are larger than their eyes while those of females are smaller. Distribution and habitat The river frog is endemic to the Atlantic and Gulf coastal plains of the southeastern United States. Its range at least formerly extended southwards from the southern part of North Carolina to southeastern Mississippi and northern Florida; it is now thought to have been extirpated from North Carolina due to habitat loss. Its typical habitat is marshes and other wet locations with emergent vegetation near streams, rivers, ponds and lakes. Biology Adult river frogs have a home range of about . They are largely nocturnal and feed on insects and other invertebrates, as well as small vertebrates, including frogs. They spend much of their time in water and are relatively bold. During hot weather they are normally found sitting in moist or wet places, presumably to avoid desiccation. When the temperature falls below about they are no longer to be seen in their normal habitat and are likely to be seeking refuge from the cold under water. Breeding takes place between April and August with