They start off cute, but the fear is that they could soon be in our waterways, gobbling up indigenous wildlife and possibly transmitting salmonella to people. Red-eared slider turtles have become pests in South America, Australia and Europe, and they might establish wild populations in South Africa too.Department of Environmental Affairs biosecurity unit officer Warren Schmidt urged people not to buy them as pets, as conservationists fear that when people tire of them they are dumped in rivers, where they can threaten indigenous wildlife.The baby turtles have bright green heads with yellow stripes for the first year of their life, but as they grow they lose their bright green colour making them less popular as pets, Schmidt explained.They can grow to the size of a dinner plate and have a ferocious appetite, which includes fish and even vegetation. With three egg-laying sessions a season, they simply outcompete local terrapins.The Times has seen a number of adverts on Gumtree in which people are selling red-eared slider turtles, even though it is against the law to trade and keep them.Schmidt said: "Adults end up in reptile parks, zoos or animal shelters. They may even be released into wetlands, and this practice may lead to an invasion risk." Sliders are being imported illegally. There is no evidence of them being bred locally."..