BULLFROGS OVERRUN FRANCE

Wildlife experts say the Californian frogs are threatening to disrupt the ecology of southwest France by eating lizards, fish and small birds.

It is illegal to import the bullfrogs, but colonies have developed after a small number were released as a joke in a private pond in the early 1980s. Their eggs are carried from pond to pond by birds.

Environmental officials say previous efforts to destroy them using electric poles proved unsuccessful.