In the summer, just around dusk, a chorus of frogs begin to vocalize on Webster Lake. In our cove, a deep bass voice, much like the roar of a bull, chimes in after the others are in full voice. This singer is the American bullfrog or simply bullfrog, as most of us call it. A familiar amphibious frog found in the United States and Canada is a member of the family Ranidae, or “true frogs”. Native to eastern North America its natural range extends from the Atlantic seacoast to as far west as Oklahoma and Kansas. Recently it was introduced to Nantucket Island, Arizona, Utah, Colorado, Nebraska, Nevada, California, Washington, and Hawaii. It is considered an invasive species in these states, as it may outcompete native amphibian species, upsetting the local ecological balance. In some foreign countries such as Mexico, China, South Korea, and Argentina the bullfrog was intentionally released, either as a food source or as biological control agents of sorts.
So how do you spot a bullfrog? Look for a colorful frog with olive-green back and sides and brownish markings. On the bullfrog’s belly, it will be white with spots of gray or yellow. Specifically, the upper lip is quite often bright green with the lower lip much paler. Of note, the male’s throat is yellow and he is smaller than the female overall. Inside the frog’s mouth are tiny teeth used to grasp little objects. The bullfrog’s brown eyes protrude and have almond-shaped irises. You will find the eardrums (tympani) just behind the eyes and dorsolateral skin folds end near them. The tympani of a male are larger than his eyes, where a female is smaller than her eyes. Limbs on the bullfrog are either blotched or have gray bands. The forelegs are sturdy and short, with the hind legs long and lean, able to jump distances 10 times their body length. Only the back toes are webbed except for the fourth toe. Most bullfrogs measure around 3.6 to 6 inches end to end. Growth is rapid the first eight months of life and weight increases from.18 ounces to 6.17 ounces. A larger, mature bullfrog can weigh in at 1.5 pounds and up to 8 inches.
Found in large, permanent bodies of water, such as ponds, swamps, lakes, and streams, a male bullfrog will defend his territory during the two to three-month breeding season. This season is anywhere from late May through July. Males will claim sites usually spaced some 9.8 to 10.7 feet apart. They call loudly using at least three different territorial calls serving not only as threats to other males, but to attract females and encounter calls which precede combat.
Male bullfrogs form into groups called choruses. These choruses are dynamic, forming and remain together for a few days. After the short period, they move on to form new choruses with different males. To establish dominance within a chorus the male demonstrates a variety of aggressive behavior, especially visually. Territorial males have inflated postures to show their yellow colored throats, while non-territorial males stay in the water with just their heads in view. When two dominant males come in contact they wrestle! After all the male jousting, a female will finally select a mate. When done, she deposits her 20,000 or so eggs in his territory in shallow water.
As a young boy growing up on Table Rock Lake in Missouri, I remember many a night when my Dad, two brothers and I went “frogging”. American bullfrogs are often found on the dinner table, especially in the Midwest and in Southern parts of the United States. When the deep call is heard, a light is shone on the frog temporarily blinding him. Then, when approached slowly, carefully, and quietly, the bullfrog is gigged with a multi-tined spear (if legal), grasping gigs or by hand capture. Normally the rear legs are eaten, much like small drumsticks and cooked in the same manner. A little trivia – the American Bullfrog is the state amphibian of Missouri, Ohio, and Oklahoma.
Most of us who grew up in the United States share another memory of the American bullfrog – dissection in Biology class. Not one I’d care to repeat, thank you!