northern leopard frog

LC - Least Concern

N5 - Secure

S4 - Apparently Secure

not listed

Northern leopard frog is a slim, medium-sized, widely recognized, spotted frog. It is the most common frog in Minnesota.

An outbreak of deformities in this species was discovered by school children in LeSueur, Minnesota, in 1995. The Minnesota Pollution Control Agency researched the problem from 1997 through 2000, when funding for the research was discontinued. The cause of the malformations remains unknown. According to the National Biological Information Infrastructure (NBII), research suggests that there is no single cause. The four major environmental factors contributing to the malformations are contaminants, nutritional deficiencies, parasites, and injuries from predators.

Adults are 2″ to 3½″ long at maturity. Males are smaller than females.

The back (dorsal surface) is smooth to moderately rough. Background color and spotting is variable. Most adults have 2 to 4 rows of black spots on a green background. Some have a greenish-brown or brown background, some have no dorsal spots, and some are brown with flecks of white, brown, or black between the spots. Juveniles may have few or no dorsal spots. The spots on all adults have a whitish or yellowish bordered. Prominent folds on each side of the back (dorsolateral) extend from the head to near the vent. The folds are light on top and dark at the base. They do not angle inward near the vent (anal opening). Males have a pair of inflatable vocal sacs on their shoulders. During breeding season these appear as areas of loose skin.

The belly is white or cream-colored.

There is a white stripe in the upper jaw. The ear covering (tympanum) is smaller than the eye.

The hind legs have dark horizontal bands. The inside of the thighs of the hind legs are pale with a greenish tint. The feet are webbed. Males have thick, dark thumb pads.

There are no recognized subspecies of northern leopard frog but there are four color morphs. Most adults have 2 to 4 rows of black spots on a green background (green morph). Some adults have a greenish-brown or brown background (brown morph). The Burnsi morph is brown or green with no dorsal spots. The less common Kandiyohi morph has black mottling or additional black spotting between the spots.

2″ to 3½″

A low pitched snore, lasting 2 to 4 seconds, and occasional clucks or croaks.

Pickerel frog (Rana palustris) has a light tan background. The spots are squarish. The inside of the thighs of the hind legs are bright yellow. They are found only in trout streams in southeastern Minnesota.

Damp woodlands and grasslands, always near lakes, ponds, rivers, slow streams, marshes, or wetlands.

5 to 7 years

Adults breed in April and May. With the male still attached, the female lays a single round mass of between 300 and 6,500 black eggs, attached to vegetation just below the water surface. The eggs hatch in 1 to 2 months and tadpoles metamorphose into adults in about 50 days, depending on the weather. After metamorphosis they leave the pond to feed on dry land and to migrate. Mass migrations often occur after heavy rains.

Adults reach sexual maturity in 2 or 3 years. They hibernate usually in deep water that does not freeze completely. They live 5 to 7 years.

Algae, plant tissue, organic debris, and probably some small invertebrates

Insects, spiders, snails, earthworms, and other small terrestrial invertebrates.

Sources

7, 13, 24, 29, 73.

Very common

Genus
In 2006, Frost et al. transferred most North American true frogs from the genus Rana to Lithobates, a controversial decision initially met with resistance. While Stuart, Pauly et al., and other systematic reviews rejected the change in 2008 and 2009, the transfer has since gained near-universal acceptance by 2024. Amphibian Research and Monitoring Initiative (ARMI), Amphibian Species of the World, Catalog of Life, GBIF, ITIS, NatureServe, NCBI, and UniProt, all use the name Lithobates pipiens.

In 2016, a consortium of Rana researchers from Europe, Asia, and North America showed that transferring the species to Lithobates caused problems of paraphyly in other genera. In that same year, Yuan et al. returned all North American true frogs to the genus Rana, using subgenera for all of the well-defined species groups within Rana. AmphibiaWeb uses the name Rana pipiens.

I used to see all the time as a child, then none for years. Recently I've seen two. This one at the Crow Wing State Park.

Very abundant in Buffalo River State Park especially along the embankment of the river.

Kandiyohi morph

Burnsi morph

Green Morph

Brown Morph

Location: Crow Wing State Park

I used to see all the time as a child, then none for years. Recently I've seen two. This one at the Crow Wing State Park.

Location: Buffalo River State Park

Very abundant in Buffalo River State Park especially along the embankment of the river.

Location: Minnesota Valley National Wildlife Refuge, Long Meadow Lake Unit

Location: Lake Harriet Gardens, Minneapolis MN

Location: Cottage Grove

Location: Big Stone National Wildlife Refuge

The Northern Leopard Frog jumped in the other tire track of a service road in The Big Stone National Wildlife Refuge. It is a species of the True Frog family, native to North America and the state amphibian of Minnesota.

Location: Lyndale Park, Minneapolis, MN

Location: Woodbury, Minnesota

Location: Lebanon Hills Regional Park

Location: Lake Harriet Gardens, Minneapolis MN

Location: Long lake, Grandy, MN

always surprised to see this frog.  Not very many around anymore.

Location: Pennington Co Mn

Location: Kandiyohi County

Location: Ramsey County