I haven’t been to the Campus Pond at the University of Massachusetts in many weeks now, but back on June 8 I was treated to a large, very cooperative amphibian as a photo subject during my lunch hour. The bullfrog, Rana catesbeiana, is native here, but elsewhere in North America, where it has been introduced, it might better be called the “bully” frog.
The species is named for the early English naturalist Mark Catesby who explored the southeast United States in the early 1700s, documenting his findings in words and illustrations published as Natural History of Carolina, Florida, and the Bahama Islands. Just like its human namesake, the frog has had “legs” to parts of the world far removed from its native eastern U.S. haunts.
It has, in fact, been those meaty hind legs that have caused the dispersal of the bullfrog around the globe. Prized as a delicacy, frog legs are a staple appetizer on many a restaurant menu. It is far less expensive to harvest the amphibians locally than to import them, so consequently the bullfrog was introduced to various new territories including the western U.S. and British Columbia, Cuba, Jamaica, Mexico, South America, Europe, Asia, even Hawaii.
That humans prey on bullfrogs, along with herons, raccoons, snakes, and other animals, is not enough to mitigate the effects of what the bullfrogs themselves eat: which is nearly anything and everything. Where bullfrogs have been introduced, native wetland fauna can suffer dramatically.
Bullfrogs have been at the least implicated in the decline of the western pond turtle in the Pacific Northwest (they eat the hatchling turtles), the Mexican garter snake in parts of Arizona, New Mexico, and Mexico, and native frog populations in California.
Any animal smaller than the bullfrog is fair game, though, and even tarantulas are on the menu, along with various large insects, small rodents, and birds.
I have a hard time now hearing that deep bass call of “jug-o-rum” without cringing a bit. Every organism surely has its place, but when Homo sapiens extends the boundaries of place for an animal like the bullfrog, all hell can break loose in the aftermath.