Snapping turtles originally come from the Americas, but turned up in Japan as pets in the 1960s, Kyodo news agency reports. Some turtles must have escaped to the wild, as there were an estimated 1,000 turtles roaming the Chiba Prefecture 10 years ago. The turtles have been classed in Japan as an invasive species and are eating up fish, bird and weed stocks, and chewing their way through fishermen's nets.