Lithobates pipiens

A slim, long-legged, green or brownish frog usually with well-defined, pale-bordered, oval or round dark dorsal spots; white stripe on upper jaw; white or cream below; well-defined, pale dorsolateral ridges that are not inset at the posterior end; dark dorsal spots may be reduced or absent in young; during the breeding season, adult males have swollen, darked thumb bases and usually have vestigial oviducts; adults generally are 5-9 cm in snout-vent length, sometimes up to 11 cm (Stebbins 1985). In Minnesota and adjacent states, the dorsum sometimes has few or no dark dorsal spots or much dark pigment between the dark spots (Conant and Collins 1991).

Differs from RANA PALUSTRIS in having rounded rather than squarish dorsal spots and in lacking yellow or orange pigment on the usually concealed surfaces of the hind limbs and groin. Differs from other leopard frogs as follows: RANA BLAIRI is never green, usually has a distinct pale spot on the eardrum, has the posterior end of the dorsolateral ridges inset or angled inward, and lacks vestigial oviducts in males. RANA CHIRICAHUENSIS has a "salt-and-pepper" pattern of small tubercles on the back of the thighs, and stockier proportions (Stebbins 1985). RANA ONCA is smaller, with shorter legs, the spotting toward the head often is reduced, and the underside of the hind limbs is yellow to yellow-orange (Stebbins 1985). RANA YAVAPAIENSIS is stockier and paler (Stebbins 1985). RANA BERLANDIERI is paler and has the dorsolateral ridges inset medially at the rear end.

Northern leopard frogs live in the vicinity of springs, slow streams, marshes, bogs, ponds, canals, flood plains, reservoirs, and lakes; usually they are in or near permanent water with rooted aquatic vegetation. In summer, they commonly inhabit wet meadows and fields. The frogs take cover underwater, in damp niches, or in caves when inactive. Wintering sites are usually underwater, though some frogs possibly overwinter underground.

Eggs are laid and larvae develop in shallow, still, permanent water (typically), generally in areas well exposed to sunlight. Generally eggs are attached to vegetation just below the surface of the water. In northern Minnesota, successful reproduction in acidic bog water either does not occur or is a rare event (Karns 1992).

In Michigan, the average nightly movement during rain was 36 m, occasionally moved more than 100 m. See Mazerolle (2001) for information on movement patterns of frogs in fragmented peat bogs in New Brunswick.

The time of egg deposition varies with latitude and elevation. Egg deposition occurs typically in April in southern Quebec, New York, and the Great Lakes region, late April to late May farther north in Manitoba and Nova Scotia (see Gilbert et al. 1994). In Colorado, eggs are laid mainly in early spring at low elevations, in late spring in the mountains (Hammerson 1999). Breeding often peaks when water temperatures reach about 10 C. At a particular site, egg deposition generally occurs within a span of about 10 days. Egg masses include several hundred to several thousand ova. Aquatic larvae metamorphose into small frogs in early to late summer, a few months after egg deposition. Females are sexually mature usually in two years in most areas, three years in high elevation populations. Density of egg masses often reaches a few hundred per ha in favorable habitat, sometimes >1000/ha.