They're not everybody's cup of tea but snakes play an important role in our countryside. But in recent years the native adder population has been decreasing.
There's been a severe decline in the Wyre Forest in Worcestershire.
Specialists at the West Midlands Safari Park say the number of adder sites in the forest has dropped from 36 to just 3 in 12 years.
They blame it on the destruction of their natural habitat and an increase in the buzzard population.
It's lead to the creation of a special breeding programme at the Safari Park.
Three pregnant female adders are being kept safe in special pods covered by netting. They're due to give birth next month.
The snakes will spend the winter in the adder pods and staff will release them back into the forest next spring.