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American bullfrog

If you’re from the Chicago area, “frog” probably equates with the big, green, slippery-as-all-get-out American bullfrog, Rana catesbeiana.

Bullfrogs are indeed the largest frogs in these parts (and in North America), growing to a whopping 6 inches or more, plus long, strong legs. Their deep, booming “bur-rum” — not some timid “ribbit” — sounds around local rivers and ponds in the early summer as males go a-courtin’.

Males are territorial and will body slam other males that invade their territory. From May to July, their basso profundo calls attract females, who lay several thousand eggs in large, gelatinous masses that can measure a yard across. The eggs hatch into tadpoles that spend the summer and all the following spring in the water. Even as tads, bullfrogs are chunkers, reaching 6 inches from head to tail. They lose the tail and the gills and join the ranks of the air-breathing and land-walking (well, -jumping) in mid-to-late summer of their second year. It takes them several more years to mature.

Bullfrogs are known for their voracious, if indiscriminate, appetites. As tadpoles, they eat mostly algae. Adults eat just about anything they can catch and cram in their mouths, including small turtles, garter snakes, ducklings and fellow frogs. In turn, bullfrogs are on the menus of herons, bigger snakes and people. In the 19th century, San Franciscans, flush with gold rush money, took a fancy to French cuisine and quickly depleted the local frog population. Bullfrogs were imported from the eastern United States and plopped into California lakes and ponds in a form of passive frog farming. While plenty of meaty frog legs went to the table, the aggressive newcomers adapted readily, outcompeting — and eating — the remaining native frogs.

Bullfrogs remain a scourge in California, as well as in Oregon and Washington, today. Around here, however, these natives equate with healthy ponds, rivers, lakes and wetlands. Don't have a pond in your backyard? Visit (and hear) bullfrogs in Waters of the World.


Check out photos, videos and stories of other Shedd frogs, like the poisonous dart frogs.

One of Shedd's bullfrogs made veterinary medical history. Read more.

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