Adder snake
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DNA test to protect adders - UK's only venomous snake

Adders are the UK's only venomous snake and were once a common sight in the British countryside.

But in the past 50 years their numbers have halved as they struggle to adapt to changes in their habitat.

Scientists are now adopting a high-tech method to try to protect them.

The BBC's Louise Hubball reports from a nature reserve in Somerset.