Mature members of this species are medium-sized, Green Frogs with irregular dark spots. Dorsal color ranges from green to brownish with a light underbelly. The spots typically have a light "halo" or greenish outer edge that is often used to distinguish this species from other leopard frogs. The tympanum is smaller than the eye and lacking a distinct light center. Dorsolateral folds are present and are usually light in color. They can reach lengths of about 2-3.5 inches.
Northern Leopard Frogs lay their eggs in globular masses, which often contain several thousand eggs. They are attached to aquatic vegetation or debris in shallow water. Larvae, or tadpoles, of this species have tails lighter in color than their bodies. They can grow to be around 2 inches long.
Both the Plains (Rana blairi) and Southern (Rana sphenocephalus) Leopard Frogs are very similar in appearance to this species. Both other species lack the green "halos" around each spot that this species has and they tend to have a light center to the tympanum that this species lacks. The dorsolateral folds of the Plains Leopard Frog are broken and inset near the hind legs. However, these characteristics are somewhat plastic (variable) and may not always be the same. The vocalizations of this species are somewhat distinct, but require careful study before making a definitive identification as they are very similar to the other leopard frog species' calls. The Pickerel Frog (Rana palustris) is similar in appearance, but has more rectangular, organized blotches and a bright yellow wash around its groin and rear legs.
The call of the Northern Leopard Frog is often described as a snore, which lasts three or more seconds. It is sometimes trailed by a series of short grunts. Listen to the call courtesy of the Indiana DNR.
Ecology and Conservation
Northern Leopard Frogs typically inhabit marshes, wetlands, and wet meadows, though they can occasionally be found in slow-moving streams and inlets of larger rivers. When startled, these frogs will often jump into tall grasses rather than into the water to escape. Minton notes that they stick to their aquatic habitats in the spring and fall, moving into grassy areas in the summer, often quite far from water. Northern Leopard Frogs are active from early spring (March/April) to late fall (October), though they can be encountered on warm winter days. Northern Leopard Frogs feed on a wide variety of small invertebrates, but they will eat other small frogs as well.
Northern Leopard Frogs breed in shallow ponds and wetlands. Once they are deposited, the eggs take a week or two to develop before hatching, and tadpoles complete metamorphosis after two or three months. In Indiana, this frog breeds from late March to early May following rainy weather.
This species has declined throughout much of its range and all of the reasons for this decline are not yet clear. In Indiana, there have been noted population declines and because of this, it is considered a species of special concern. Loss or degradation of wetland breeding habitat may be largely to blame for this decline, though disease may play some role.
This species is found broadly throughout the northern third of the United States and into Canada. In the west, their range extends into eastern California and in the east they are found from Maine to West Virginia. They also occur up and down the Rocky Mountains from Canada down to New Mexico and west Texas.
Northern Leopard Frogs can also be found throughout the northern half of Indiana, with their range extending further south in the eastern part of the state. There is a single, disjointed record for Floyd County that may or may not represent a native, extant population. They have become increasingly uncommon in recent years.
The Northern Leopard Frog does not have any subspecies. Frost et al. (2006) recommended placing these frogs in the genus Lithobates, but other authors argue against this, instead suggesting the recognition of subgenera within the monophyletic Rana (e.g., Pauley et al. 2009; Yuan et al. 2016). Northern Leopard Frogs belong to the family Ranidae, which is diverse and widespread worldwide and includes eight species of frogs in Indiana.
Brodman, R. 2003. Amphibians and Reptiles from Twenty-three Counties of Indiana. Proceedings of the Indiana Academy of Science 112:43-54.
Conant, R. and J. T . Collins. 1998. Reptiles and Amphibians of Eastern and Central North America. Third Edition, Expanded. Houghton Mifflin, New York, NY.
Frost, D. R., T. Grant, J. Faivovich, R. H. Bain, A. Haas, C. F. Haddad, R. O. De Sa, A. Channing, M. Wilkinson, S. C. Donnellan, and C. J. Raxworthy. 2006. The amphibian tree of life. Bulletin of the American Museum of Natural History:1-291.
Minton, S. A. Jr. 2001. Amphibians and Reptiles of Indiana. Indiana Academy of Science, Indianapolis, IN.
Pauly, G.B., D. M. Hillis, and D. C. Cannatella. 2009. Taxonomic freedom and the role of official lists of species names. Herpetologica 65:115-128.
Pierson, T. 2012. Lithobates pipiens. Northern Leopard Frog. Geographic distribution. Herpetological Review 43:300.
Yuan, Z. Y., W. W. Zhou, X. Chen, N. A. Poyarkov, Jr., H. M. Chen, N. H. Jang-Liaw, W. H. Chou, N. J. Matzke, K. Iizuka, M. S. Min, and S. L. Kuzmin. 2016. Spatiotemporal diversification of the true frogs (genus Rana): a historical framework for a widely studied group of model organisms. Systematic Biology, 65:824-842.