The bullfrog is native to North America. Bullfrogs have been widely introduced and their current range is greater than its original, naturally limited range. They are found throughout the United States and other countries.
Bullfrogs live in aquatic habitats. They absorb oxygen and eliminate carbon dioxide through their moist skin, the lining of the mouth, and the lungs. When in the air, as opposed to underwater, frogs continuously elevate and lower the floor of the mouth, which serves to ventilate the mouth cavity and exchange gases through the richly vascularized lining of the mouth. Periodically, the regular rhythmic pumping of the floor of the mouth is interrupted by a deeper lowering of the throat at the extreme of which the glottis (closing off the airway to the lungs) opens and the throat muscles contract vigorously to force air from the mouth into the lungs (the nostrils are closed off). This lung ventilation may be performed several times after which the shallow buccal ventilation resumes. Lacking ribs, frogs must supply the pressure to force air into their lungs (whereas mammals can enlarge the cavity surrounded by the rigid rib cage and allow the atmosphere to supply the pressure).
Breeding begins in late spring or early summer. Males defend and call from territories. The call, reminiscent of the roar of a bull - hence the frog's common name, attracts the female into a territory where mating takes place. A female may produce up to 20,000 eggs in one clutch. Eggs hatch in 3-5 days. Time to metamorphosis ranges from a few months in the southern to 3 years in the northern parts of the geographic range.
Maximum lifespan in the wild is estimated at 8-10 years, but at least one captive lived almost 16 years. Stomach content studies going back to 1913 suggest that bullfrog preys on any animal it can overpower and stuff down its throat. Bullfrog stomachs have been found to contain rodents, small turtles, snakes, fish, tadpoles, snails, beetles, frogs including bullfrogs, birds, even bats, as well as the many invertebrates which are the usual food of bull frogs. The specialized ability of bullfrogs to capture submerged and large strong prey comprises a pronounced biting motor pattern that follows up on the initial and typical bull frog tongue strike.
The bullfrog, like many other aggressive frogs, is an ambush predator. The frog waits in ambush, relatively motionless, until moving prey appears. The frog performs a single orienting bodily rotation ending with the frog aimed towards the prey. This is followed by approaching leaps, if necessary. Once within striking distance, the bullfrog emits its feeding strike, which consists of a ballistic (eyes closed as during all leaps) lunge that ends with the mouth opening, extension of the fleshy and mucous-coated tongue upon the prey, often engulfing it, while the jaws continue their forward travel to close (bite) in close proximity to the prey's original location just as the tongue is retracted back into the mouth, prey attached. Large prey that do not travel entirely into the mouth are literally stuffed in with the forearms. In laboratory observations, bullfrogs taking mice usually dove underwater with prey in mouth, apparently with the advantageous result of altering the mouse's defense from counterattack to struggling for air. The tiny teeth of bullfrogs are useful only in grasping.