The American bullfrog is threatening to drive some French amphibians to extinction, a French environmental group warned yesterday. The group, Cistude, asked for the French government’s help in eradicating the bullfrog, which has invaded the lakes and ponds of wine country around Bordeaux. “We’ve seen in other parts of the world what harm the American bullfrog can do if it isn’t stopped. Other amphibians just disappear,” said Christophe Coic, the director of the group. He said the bullfrog, which can grow to 24 inches and weigh more than 4 pounds, eats insects, other amphibians, small mammals, and even ducklings and goslings.