The Northern viper, measuring up to 60cm long, is the only snake present in the National Park.
As its habitat it favours damp meadows, the sunny edges of forests and boulder fields up to an altitude of nearly 3000m. If disturbed vipers can cause harm to human beings. They use their venom to kill their prey - mice, small birds, frogs and common lizards.
In mountain regions the northern viper bears from 4 to 18 young every 2 to 3 years. Unlike most other reptiles, vipers are viviparous.
Snakes are poikilothermic; their body temperature varies with the temperature of the surroundings. They spend the cold winter months in a period of dormancy, underground. On emerging from their winter sleep vipers mate in May.
Vipers are very well camouflaged and are easily overlooked. They often lie sunning themselves in the grass, curled up and motionless.