http://www.bbc.co.uk/nature/life/Vipera_berus#p00hdqgt Adder BBC Nature Wildlife: Adder Adder Adder http://www.bbc.co.uk/nature/life/Vipera_berus Adder Adder http://www.bbc.co.uk/nature/life/Vipera_berus#p00hdqgt