Frogs and Toads in Your Pocket: A Guide to Amphibians of the Upper Midwest

Bullfrog: Lithobates catesbeianus

Bullfrog Lithobates catesbeianus range: IL, IN, IA, KS, MI, MN, MO, NE, OH, SD, WI size: 3 1/2–8 inches description: Large green, olive, or brown nonclimbing frog sometimes with brown or black spots or blotches on back, especially young frogs. Tops of legs may have dark bars. Lacks dorsolateral fold, ridges border tympanum . Belly white to yellow, sometimes with spots. Male tympanum distinctly larger than eye, yellow throat. Female tympanum approximately same size as eye, white throat. Webbing on hind foot nearly complete. habitat: Permanent lakes, ponds, marshes, rivers, streams voice: Loud series of bass notes sounding like “jug-o’-rum” and resembling the bellowing of a bull. When frightened, often gives a single “yelp” as it jumps into water. natural history: This large frog has been introduced by humans into many areas where it has resulted in the loss of smaller native frogs. It is an aggressive predator that will eat anything it can catch, including insects, other frogs, snakes, small turtles, mice, and birds. Breeds late April to August. Tadpoles overwinter and transform the following summer. similar species: Bronze and green frogs have dorsolateral folds along both sides of back. Bronze frog Lithobates clamitans range: Bronze frog (L. c. clamitans): IL, MO; green frog (L. c. melanotus): IL, IN, IA, KS, MI, MN, MO, OH, WI size: 2 1/4–4 1/4 inches description: Medium green, olive, or brown nonclimbing frog with dark spots on back and sides and dark crossbars on tops of legs. Occasionally, some individuals lack yellow pigment in skin, resulting in partially or completely blue back. Upper jaw mottled. Dorsolateral fold ends at midback. Belly white, sometimes with light mottling. Male tympanum distinctly larger than eye, bright yellow throat. Female tympanum approximately same size as eye, white or pale yellow throat. Webbing on hind foot approximately halfway to tip of 2d toe. habitat: Shallow, weedy areas around lakes, ponds, rivers, creeks, swamps, marshes, roadside ditches voice: Single explosive “plunk,” sounding like a plucked banjo string. Calls may be repeated in series. When frightened , often gives a single “eek” as it jumps into water. natural history: Feeds primarily on insects and other invertebrates, but adults may eat other frogs. Breeds May to mid September. Tadpoles overwinter and transform the following summer. similar species: Bullfrog lacks dorsolateral fold. Mink frog has spots or lengthwise stripes on legs, not bars; webbing on hind foot extends to tip of 5th toe; musky, rotten onion, or minklike smell when handled; plain green upper jaw. ▼ ▼ ...