The Differences Between Pig Frogs & Bullfrogs

The pig frog and bullfrog are both North American species from the family Ranidae, known as riparian, or true frogs. The two species further belong to the genus rana which means they share several characteristics. Frogs of the rana genus tend to have long rear legs, narrow waists and no webbing between the digits of their front limbs.

  1. Physical Differences

    • The pig frog and bullfrog look similar in appearance, but several differences are evident upon closer inspection. The bullfrog is larger, growing up to 8 inches in length and up to a pound in weight. The pig frog grows to around 5 inches long and is less bulky. It also has a more narrow, pointed head than the bullfrog and more extensive webbing on the rear feet. Males of both species are recognized for having larger ear circles on the side of their heads compared to the eyes. Females have ear circles and eyes that are generally the same size. The pig frog also has dorsal ridges along its back that the bullfrog lacks.

    Habitat and Ranges

    • The bullfrog is by far the most widespread of the two species, with the pig frog living only in the southeastern U.S. from east Texas to central South Carolina and throughout all of Florida. The bullfrog ranges from Nova Scotia to Florida and as far west as the Rockies. It has also been introduced into a few west coast states such as California. Both species live in or near water and can be found in a variety of wetland habitats.

    Diet and Predators

    • The pig frog, the smaller of the two species, tends to eat smaller prey such as insects, worms and crustaceans. The larger bullfrog will eat almost anything it can fit in its sizable mouth, such as snakes, fish, smaller frogs and occasionally small mammals. Both species are hunted by humans for food, specifically for their legs. As neither has a poison to deter predators, a large range of animals feed on both, but the bullfrog is safe from some of the smaller predators that might eat the pig frog.

    Life Cycle

    • The two species tend to have similar reproduction methods and seasons, both starting around May. The bullfrog produces twice as many eggs on average -- 20,000 compared to the pig frog's 10,000. The bullfrog's eggs take a day or so longer to hatch out than those of the pig frog. They also take longer to mature from tadpoles into adult frogs, averaging two to three years compared to the pig frog's one.

    Vocalizations

    • As both species are nocturnal it may not be possible to tell the difference visually in the dark, but the two frogs have distinct vocalizations that are noticeably different. The bullfrog's call is described as a long and low, bellowing "jug-o-rum" sound. The pig frog, as is apt for its name, sounds like a pig grunting, so it is not difficult to know which frog you are hearing.