Identification

This non-descript frog is found peripherally in Indiana and is known from only a handful of sites. Like their more widespread counterparts, adult Plains Leopard Frogs have dark, irregular dorsal blotches. In this species, the spots have no light borders and there is usually a spot on the snout. The key in distinguishing this species from the more common leopard frog species in Indiana is that the dorsolateral folds are broken and inset posteriorly. The tympanum has an obvious light center and a distinct line along the upper jaw is present (as it is in other leopard frogs). Plains Leopard Frogs grow to around 2 in (45-65 cm) long.

Plains Leopard Frogs deposit globular egg masses in shallow water, similar to Indiana's other leopard frog species. Larvae are also similar to other species, but more slender and rounded with a noticeably more subterminal mouth than the larvae of the Northern Leopard Frog (L. pipiens). They grow to approximately 2 in (~60 mm) in length.

Both Northern and Southern Leopard Frogs are very similar in appearance to this species. In general, other leopard frog species tend to have more green coloration whereas plains leopard frogs are uniformly brown. While Plains Leopard Frogs lack the light borders around their spots that Northern Leopard Frogs have, both species have a spot on their snout (which Southern Leopard Frogs usually lack). The dorsolateral folds of this species are broken and inset near the hind legs, separating it from all other frogs in the state (see images below). The vocalizations of Plains Leopard Frogs superficially resemble those of Southern Leopard Frogs and the two could be confused. This species has been found alongside both northern and Southern Leopard Frogs in Indiana, though all three species are not known to co-exist anywhere in the state. The Pickerel Frog is similar in appearance, but has rectangular blotches running down the back in organized rows and a bright yellow wash on the groin and rear legs. Crawfish Frogs are much larger and have a blunt, rounded snout and a more reticulated pattern between its dorsal spots.

Call

The call of this species has been described as a "chuck-chuck-chuck", lasting about a second.

Listen to the call courtesy of Indiana DNR.

Ecology and Conservation

In other states, Plains Leopard Frogs are found in association with open habitats such as old fields, grassland, marshes, and along the margins of highways and agricultural areas. They apparently avoid forested areas and are scarce in and around plowed fields. They require wetlands or ponds in which to breed and are rarely found far from water. Morphological evidence suggests that this species is more adapted for breeding in streams than the other leopard frogs in the state and most Indiana records come from stream and river margins or floodplains. Historically, this species was almost certainly a prairie inhabitant, but has adapted to more disturbed environs following the loss of most native prairie habitat. Plains Leopard Frogs breed from March to May in still water. They begin to breed with the first warm, spring rains. While they may be found near streams, they are primarily a wetland breeder and will utilize marshes, ponds, and low flooded areas. During their active season, they prey on crickets and earthworms, among other invertebrates.

Because records for Plains Leopard Frogs are few and scattered in Indiana, virtually nothing is known about its conservation status. This frog may have experienced population declines associated with the loss of Indiana's native grasslands, however, since Indiana lies on the eastern periphery of the species' range it is possible that the frog was never a common resident in the state. In Indiana, it is sympatric with other leopard frog species and will occasionally hybridize with them. Plains Leopard Frogs are considered a state endangered species in Indiana due to a scarcity of records.

Distribution

This frog is a species of the Great Plains and occurs throughout the central United States. They are found from New Mexico and Texas, north into South Dakota and east into Illinois and the western half of Indiana. The range of this species in Indiana is not well-understood. There are only a few records scattered along the western (primarily northwestern) part of the state with the exception of a single Tipton County record. The range of this frog coincides roughly with the eastern extent of the prairie peninsula which reached its easternmost limit in northwestern Indiana. Where they have been found in Indiana, Plains Leopard Frogs occur alongside either northern or Southern Leopard Frogs which may partially account for its lack of documentation in the state. The only recent records for this species are from Vigo and Newton Counties. In Vigo County, the frogs are sympatric with Southern Leopard Frogs while they are sympatric with Northern Leopard Frogs in Newton County.

Taxonomy

There are no recognized subspecies of the Plains Leopard Frog (Rana blairi). 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). Plains Leopard Frogs belong to the family Ranidae, which is diverse and widespread worldwide and includes eight species of frogs in Indiana.

Literature Cited

Burris, J. and A. Hoffman 2014. Lithobates blairi. Plains Leopard Frog. Geographic Distribution. Herpetological Review 45:87.

Brown, L. E. and M. A. Morris. 1990. Distribution, Habitat, and Zoogeography of the Plains Leopard Frog (Rana blairi) in Illinois. Illinois Natural History Survey Biological Notes 136.

Conant, R. and J. T . Collins. 1998. Reptiles and Amphibians of Eastern and Central North America. Third Edition, Expanded. Houghton Mifflin, New York, NY.

Engbrecht, N. E., J. A. Crawford, and M. J. Lannoo. 2009. Lithobates (=Rana) blairi. Plains Leopard Frog. Geographic Distriubtion. Herpetological Review 40:446.

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.

Frost, J. S. and J. T. Bagnara. 1977. Sympatry Between Rana blairi and the Southern Form of Leopard Frog in Southeastern Arizona (Anura:Ranidae). Southwestern Naturalist 22:443-453.

Hillis, D. M. and T. P. Wilcox. 2005. Phylogeny of the New World true frogs (Rana). Molecular Phylogenetics and Evolution 34:299-314.

Hillis, D. M., J. S. Frost, and D. A. Wright. 1983. Phylogeny and Biogeography of the Rana pipiens Complex: A Biochemical Evaluation. Systematic Biology 32:132-143.

Hillis, D. M. 1982. Morphological Differentiation and Adaptation of the Larvae of Rana berlandieri and Rana sphenocephala (Rana pipiens Complex) in Sympatry. Copeia 1982:168-174.

Korky, J. K. 1978. Differentiation of the Larvae of Members of the Rana pipiens Complex in Nebraska. Copeia 1978:455-459.

Kruse, K. C. 1981. Phonotactic Responses of Female Northern Leopard Frogs (Rana pipiens) to Rana blairi, a Presumed Hybrid, and Conspecific Mating Trills. Journal of Herpetology 15:145-150.

Lynch, J. D. 1978. The Distribution of Leopard Frogs (Rana blairi and Rana pipiens) (Amphibia, Anura, Ranidae) in Nebraska. Journal of Herpetology 12:157-162.

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.

Transeau, E. N. 1935. The Prairie Peninsula. Ecology 16:423-437.

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.