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Species native to the United Kingdom
Introduced or alien species
Alien species that present a threat to wildlife

American Bullfrog - Rana catesbeiana - Alien


Very large aquatic frog

Distinguishable from European species by lack of dorsal lateral fold, very large eardrum and vocal sac being beneath the chin.

The large eardrum and lack of a dorso lateral fold (see Common Frog ID page for comparison) help to distinguish this species from the superficially similar though smaller, Green Frogs such as the Marsh Frog that have been introduced to some areas and the native Common Frog.

Tends to be more uniform in colour than native and other introduced species, usually green, olive-green or brown on the dorsal surface and flanks,

Ventral surface, whitish, mottled or spotted with grey.

Adults up to 20 cm

Tadpoles up to 15 cm

Distinct cow-like call.

UK Distribution

Breeding occurred at a site on the Sussex and Kent border, efforts were made to exterminate it.


Exotic - The American Bullfrog is a voracious predator and a serious threat to British wildlife. Tadpoles of the American Bullfrog were at one time widely sold in garden centres, imports are now banned due to the risk of this invasive species establishing in the UK. Vigilance is still required as there have been reports of accidental introductions of tadpoles included with consignments of aquatic plants.

© David Bird British Herpetological Society

Bullfrog - male
© David Bird British Herpetological Society

Male American Bullfrog. Note large Eardrum and lack of Dorso lateral fold.

Release of exotic species into the wild is a criminal offence under the Wildlife and Countryside Act 1981.

This includes introduction of exotic or alien species that may already have become established.

The interpretation of "wild" in the act includes private gardens from which escape is possible.

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