Difference Between a Bullfrog & a Green Frog

The frog is a primitive survivor. It evolved about 360 to 415 million years ago, and today about 4,600 different species inhabit the earth. Humans alter the frog's habitat by introducing invaders and predators and capturing the frog for lab experiments. Two popular favorites for scientific study include the bullfrog and green frog. Although they look alike, they have some distinct differences in physical appearance, diet, communication and habitat.

  1. Physical Appearance

    • An adult bullfrog's body measures 8 inches, while green frogs measure 4 inches. Green frogs have pronounced, protruding eyes; bullfrog eyes are set deeper into the head and are less elevated. Green frogs have a variety of species with different colors and markings, compared with the standard green and brown bullfrog color. A green frog's tympanum is more conspicuous than a bullfrog's tympanum, which blends with its body color. The green frog has raised dorsal-lateral ridges that run down both sides of its legs. A bullfrog's ridges wrap around the tympanum (eardrum) and stop at the base of the eardrum.

    Diet

    • Frogs use five senses to hunt within their environment: visual, tactile, acoustic, vibration and chemical. The aggressive adult bullfrog eats anything that moves or that fits into its mouth. Its diet includes snakes, fish, small turtles, mice, small water birds, crustaceans, water beetles, dragonfly larvae, spiders and other invertebrates. Examination of a bullfrog's stomach contents revealed an appetite for spring peepers, American toads and green frogs. These aggressive jumbo frogs are cannibals that often devour their own tadpoles and larvae besides eating other adults within their species. The adult green frog eats insects, worms, beetles, bugs, spiders, ants, moth larvae, snails and sometimes small frogs and fish.

    Communication

    • Green frogs make six distinct calls to attract mating females, guard territory, or warn neighbors of predators. Bullfrogs have three distinct calls: three to six deep croaks to call mating females, a single mating "gronk," and a distinctly abrupt but forceful "bonk." Unlike the bullfrog's lengthy "mmmwwong," the green frog's mating call sounds like a deep, abrupt "guungk." Green frog calls sound like a plucked banjo "twang," while the bullfrog sounds like air whistling across the top of a soda pop bottle. A bullfrog vocalizes using deep, hoarse, abrupt sounds and usually does not sing in chorus.

    Habitat

    • Bullfrogs prefer large, vegetation-rich ponds, marshes and lakes with shady trees and bushes along the shoreline, whereas green frogs prefer small vegetative springs or lakes. Bullfrogs hibernate in permanent fresh waters, but spend summers in vegetated shoals of temporary, shallow ponds. Green frogs prefer streams, ditches and roadside ponds during the summer and winter. At breeding sites, male bullfrogs claim territories by regularly sitting at the water's edge for sometimes three weeks. Bullfrogs hibernate, breed and hunt in water. Only during torrential rains, will they leave their old habitat to look for new ponds. Green frogs spend time on the land near the water's edge or in shallow pools.