As temperatures begin to cool, that big ol’ bullfrog (Rana catesbeiana) in your neighborhood pond is thinking about retreating to the bottom of the pond to spend the winter. Bullfrogs in our area will disappear from the edges of ponds and lakes around mid-October, burrowing under the mud at the pond bottom, or under leaf litter.
The bullfrog is a common species and was originally found only in the central and eastern United States and up into Nova Scotia. Unfortunately, efforts to commercially harvest frogs’ legs from bullfrogs has led to the introduction of the species to many western states, as well as Mexico and Cuba. There is concern that introduced bullfrogs compete with and displace native frog species in these areas. And they’ll eat almost anything that happens their way: worms, large insects like dragonflies, other frogs, and even unsuspecting hummingbirds.
Not sure that what you’re seeing is a bullfrog? Bullfrogs prefer the water’s edge along a vegetated bank. When alarmed they may jump into the water or hide among the dense vegetation. Like green frogs, they are varying shades of green and brown and yellow, but green frogs have a pair of ridges that run down the back. The bullfrog does not have these ridges, though it does have a ridge of skin that runs from just behind the eye and wraps around the eardrum. Adult bullfrogs are large, with body lengths ranging from three inches to a whopping eight inches. The distinctive ‘jug-o-rum’ call of the male is quite different from the banjo-twang call given by the green frog.
Bullfrogs spend their lives around water. Unlike terrestrial wood frogs that have a frenzied breeding season in early spring in temporary water bodies, the bullfrog breeding season doesn’t need to be completed in a two to three week span. Instead, bullfrogs breed anywhere from May to July in our area and from February to October in the south. And since eggs are laid in permanent bodies of water, the tadpoles don’t need to race against the clock to develop into frogs before their pond dries up. In fact, bullfrog tadpoles can take up to two years to transform into frogs, with some spending a winter or two in the tadpole stage. Look for these huge five-inch long tadpoles along the silty bottom of their aquatic home.