Boreal Chorus Frog

Overview:

Scientific Name: Pseudacris triseriata maculata
Size: 0.7 – 1.5” (adult length
Status: Can be common to abundant locally, but many populations have recently declined, particularly in suburban and agricultural areas
Michigan State Status: Special Concern;
MDNR Wildlife Action Plan Status: Species of Greatest Conservation Need

Habitat:

Prefer marshes, meadows, swales, and other open habitats. Also may be found in wet woods or wooded swampy areas. Will largely be found under refuges such as logs, rocks, and leaf litter.

Adult Coloration:

Brown, reddish, or tan to gray or olive background color with a conspicuous white or cream stripe along upper lip, with a dark brown stripe bordering the top that runs from the nose through the eye and down to the groin. Usually three greenish-black stripes down the back, often broken into spots. Belly cream or white, occasionally with dark speckling on chest and throat.

Adult Characteristics:

Skin slightly rough though moist. Toes slightly expanded. Hind legs shorter, so locomotion is more like a hop than a leap. Males a bit smaller than females with a yellowish vocal pouch apparent as a grayish flap of skin in the throat (most visible during breeding season). Voice: Short scratchy “cree-ee-ee-ee-eek” that rises in pitch. Similar to the sound of a pocket comb being strummed with a fingernail. e.g., http://www.youtube.com/watch?v=rfseWEiUnt0

Larvae Characteristics:

Tadpoles rounded and gray or brown above, sometimes with golden mottling when older. Tail fins clear with dark speckling. Intestines visible through bronze belly. Maximum length is around 1.2”.

Species Confused With:

The Spring Peeper does not have a distinct white upper lip stripe and usually has an X-shaped mark on the back. Blanchard’s Cricket Frog has rougher skin and also does not have a white lip line or dark stripes on the back. Small Wood Frogs may be mistaken for Chorus Frogs due to similar markings on the lip, but these can be distinguished by their dorsolateral folds (raised ridges extending down each side of the back).

Distinction between subspecies:

Two subspecies of P. triseriata (sometimes referred to as the Striped Chorus Frog) occur in Michigan. Pseudacris t. triseriata is known as the Western Chorus Frog and occurs in the eastern Great Lakes region. It is very similar to the Boreal Chorus Frog but has longer hind legs (with a tendency to leap rather than hop) and usually has blacker striping on the back.

References:

Amphibians and Reptiles of the Great Lakes Region by Jim Harding
Harding, J.H. and J.A. Holman. 1992. Michigan Frogs, Toads, and Salamanders. MSU Cooperative Extension Service and MSU Museum. Extension Bull. E-2350, 144 pp.
Ruthven, A. G., H. B. T. Gaige, et al. 1912. The herpetology of Michigan, by Alexander B. Ruthven. Crystal Thompson and Helen Thompson; Memoranda towards a bibliography of the archaeology of Michigan, by Harlan I. Smith; prepared under the direction of Alexander G. Ruthven. Lansing, Mich., Wynkoop Hallenbeck Crawford, State Printers.
Holman, J. A. 2012. The Amphibians and Reptiles of Michigan: A Quaternary and Recent Faunal Adventure. Detroit, Mich., Wayne State University Press.
Conant, R., and Collins, J. T. 1998. Reptiles and Amphibians: Eastern, Central North America. Houghton Mifflin Harcourt Press.