Camp near or drive by a farm pond or lake on a summer evening, and you’re likely to hear two distinctive sounds. Bullfrogs sing a deep, booming “Jug-o’-rummm!” The sound of a loose banjo string, on the other hand, comes from an amorous male green frog.
Though similar in appearance, bullfrogs can reach a length of seven inches; green frogs top out at about four inches (size does not include the rear legs). Both sexes of bullfrogs vocalize, but the “jug-o’-rum” mating song of the male is the loudest and best known.
Other calls signal territory ownership, warning, and distress. When I first heard a bullfrog distress call at scout camp many years ago, I remember being scared and burrowing into my sleeping bag. Bullfrogs emerge in early spring, but delay breeding until late May. Their deep booming voice announces the arrival of summer. Any quiet body of water surrounded by dense vegetation is likely to shelter bullfrogs.
Farm ponds ringed with cattails and water lilies are bullfrog heaven. Males sing to attract females to their territories. Each male sings from a station along the bank that he defends and returns to night after night.
The mating dance
Mating occurs in the water. The male pounces on any female that ventures near and grabs her tightly. He fertilizes the eggs (thousands of them) as she releases them. The embrace, which is typical of frogs and toads, is called amplexus. The female simply releases the eggs on the surface of the water around pieces of aquatic vegetation.
Eggs hatch in three to five days. After spawning in late May or early June, bullfrogs sometimes repeat the process in late July.
Tadpoles reach a length of one inch by the end of their first summer. Before transforming into adults, however, they grow extraordinarily large. Bullfrog tadpoles often reach lengths of six inches or more before transforming into adult frogs after 12 to 14 months as tadpoles. Young bullfrogs then require another two years to reach sexual maturity. This means bullfrogs can be three to four years old before they breed.
Unlike most frogs, which eat small insects, spiders, and earthworms, bullfrogs are voracious predators. They attack any live animal smaller than themselves that they can swallow. Biologists have found all sorts of insects, fish, crayfish, mice, bats, small turtles, lizards, ducklings, smaller frogs (including smaller bullfrogs) and even small alligators in bullfrog stomachs.
A sit-and-wait hunting technique rewards patient bullfrogs. They sit motionless for long stretches of time, yet remain alert to movement. If danger threatens, hop, splash, and it’s off to deeper water. But if a crayfish, minnow, or insect gets too close, it’s mealtime. And beware if you have a small backyard pond stocked with bullfrogs. They do not hesitate to eat small birds, even hummingbirds, that stop by for a drink or a bath.
Search “bullfrogs eating birds” on the internet for video examples. Green frogs are essentially a smaller version of bullfrogs. In many places, they are the most common frog encountered. Walk along a farm pond, a roadside ditch, or even a deep puddle, and these are the frogs that jump from the water’s edge into the deeper water. Often they squeak as they jump. Of course, frogs make great meals for a variety of predators. Water snakes, snapping turtles, raccoons, mink, otters, alligators, owls, and herons are just a few of the predators that eat them. Humans are also on the list.
Frog legs are tasty and often found at restaurant buffets (They taste like chicken.) In fact, it is our taste for frog legs that has caused bullfrogs to become an ecological disaster in places where they have been introduced for commercial use. Native to the eastern half of the U.S., bullfrogs were imported to California in 1898 to meet consumer demand.
Since then, they’ve been released in Asia, Europe, and South America. In the absence of natural predators, bullfrogs thrive and disrupt wetland ecosystems. It’s just another example of an introduced exotic species leading to ecological chaos.
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