A SURVEY has been launched to uncover the last few strongholds of the UK’s only venomous snake.

The number of wild adders is declining nationally, but some of their last surviving habitats are in the North Pennines.

Durham Wildlife Trust is leading the Heart of Durham project, an investigation into the area’s adder population to ensure their revitalisation and long-term survival.

The adder – vipera berus – has been designated a priority species in the Durham Biodiversity Action Plan.

The investigation will focus on three sites including Tunstall Reservoir, near Wolsingham, in Weardale, Waskerley Way, at Castleside, near Consett, and Burnhill Junction, near Saltersgate, Tow Law.

The survey teams will make at least two visits a week to each site this month, as well as talking to local people to gain information about winter hibernation sites.

Adult adders can grow up to 90cm long.

Although their bite is not considered highly dangerous, there have been an estimated 14 fatalities in Britain since 1876. The last recorded victim was a five-year-old girl in 1975.

Project officer Sarah Edwards said: “The action plan states that the North-East of England is of high conservation importance for the adder, because of its relative scarcity and its apparent decline elsewhere in the UK. We believe that adders are widely distributed in the west of Durham, particularly in the dales and moors of the North Pennines, where they favour rocky tributary valleys. However, local population trends are unknown, which is why we have started this survey.”

She said knowing where the adder populations were would help the campaigners improve the snakes’ habitats and create wildlife corridors and new areas of reptile conservation.

She said: “By creating and protecting habitats, we can hopefully allow populations to expand and increase in numbers.

“The work would also create opportunities for reconnecting isolated populations, thus helping to increase the possibility of adders, slow worms and common lizards thriving in the Durham area.”

The survey is supported by Northumbrian Water, Durham County Council, Lanchester Parish Council and the Sir Tom Cowie Charitable Trust, which is funding the work.