American bullfrogs (Lithobates catesbeianus) are more commonly known just as bullfrogs in the United States and Canada. They're listed by the International Union for Conservation of Nature as a species of least concern, meaning they're not endangered. They're native to much of North America, but have also been introduced to various other countries, where they're often considered an invasive species.
Population and Range
The native geographical range of bullfrogs is from Nova Scotia in the north down through the United States and south to Veracruz in Mexico. However, they've been introduced as a non-native species to a range of other countries, and have become established in at least 15, including Spain, Greece, China and Indonesia. They're generally considered a nuisance species in these countries, as they indiscriminately eat native frog populations and can spread disease. Although their exact numbers are unknown, their population is increasing and they're thought to be common across their range.
Physical Description
The biggest of any true frogs found in North America, bullfrogs can measure up to eight inches and weigh a little over one pound. They're olive green over most of their bodies, with mottled patches of darker green, brown and black. During breeding season, males have yellow throats, whereas females have white throats. They have external ears, known as tympanums, which are circular and located on the sides of their heads. In males, these are bigger than their eyes. In females, they're of an equal size to or smaller than their eyes.
Preferred Habitat
Since bullfrogs spend much of their time in the water, they're usually found in or near lakes, streams, rivers, swamps or marshes. They prefer shallow water that's warm and still, but they're highly adaptable and are found in a range of aquatic habitats. Areas such as lakes that have been modified by humans are ideal for bullfrogs as they're generally warmer and have more vegetation to provide cover.
Predation and Predators
Bullfrogs are voracious eaters and munch their way through almost any prey they can get their mouths around. They hunt and devour fish, snakes, worms, insects, other frogs, crustaceans and small mammals. Their huge appetite poses a threat in countries where they're not a native species, as they can wreak havoc on local wildlife. Despite being fierce predators, they're also considered prey by some creatures, including herons, water snakes, raccoons, turtles and kingfishers.
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