Experts in northeastern England are trying to determine whether adders in the region are becoming overly inbred as their numbers decline. The European adder, the only venomous snake in Britain and much of Europe, has a wide range. But its numbers have fallen in England because of habitat loss and it is considered threatened. Durham County Council, the Durham Wildlife Trust and Sunderland University have joined in a project to study adders in Derwentside, Teasdale and Weardale, The Northern Echo reported. The snakes will be coming out of hibernation soon, making the spring an ideal time to launch the study. The Wildlife Trust will focus on outdoor work, looking for living and dead snakes, while university scientists work in the lab, officials said. Noel Carter, a senior lecturer at Sunderland, said there is concern that "dwindling populations will lead to inbreeding depression, a condition that could cause problems such as mutations from missing eyes to deformed spines to adders being born dead."