North American Bullfrog (Lithobates catesbeianus)

This is a very large aquatic frog distinguishable from the introduced European species by lack of dorsal lateral fold, a very large eardrum and the vocal sac being beneath the chin rather than at the side of the head.

The large eardrum and lack of a dorso lateral fold (see Common Frog for comparison) helps to distinguish this species from the superficially similar though smaller, water Frogs such as the marsh, edible and pool frog that have been introduced to some areas and of course the smaller 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, the males tend to have a yellow throat during the breeding season.

The ventral surface (belly) is normally whitish, mottled or spotted with grey. The adult frogs can grow up up to 20 cm in length while the tadpoles can grow up to 15 cm at metamorphosis which can take over three years to complete. The species has a distinctive mating call which sounds like a cow hence the name the 'Bull'frog

Bullfrog tadpole - found in Essex 2006

UK Distribution

Breeding has occurred in the past at the Sussex/Kent border - from the mid 1990's to the present an eradication programme has removed this population. A second population has been detected in the East of England since 2006 the population has since been removed. A further population has been found in the South East and efforts are now being taken to remove this population and determine whether any other populations are known from the UK.

Status

Exotic - The American Bullfrog is a voracious predator and a potential 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.

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.

Text Source RAUK http://www.herpetofauna.co.uk/bullfrog.htm