Bob Lawrence, director of wildlife at the safari park, said: "It's looking fine, but so it should be having had half of Britain's fish stocks at its mercy. "If it grew any larger it would have been a danger to shipping." He said it highlights the danger of introducing alien species into Britain's waterways, in the same way that American signal crayfish have caused such depletion to fish stocks and the UK's native crayfish. And he said the problem is only likely to get worse with global warming. "Thankfully alligator snapping turtles are a rarity in British waters - they can create havoc for native species," he told Sky News Online.