Grass snake  (Natrix natrix)

Grass snakes are difficult to observe as they are fast-moving and wary (2). Because they derive their body warmth from the environment, this snake has to bask in the sun after emerging in the morning in order to reach high enough body temperatures to be able to function efficiently and digest their prey (3). During winter, temperatures are too low, and grass snakes find frost-free places such as deep leaf litter or rock piles in which to hibernate between October and March or April (2).

Courtship and mating take place from March to June. When a male finds a receptive female, he curves his body around the female, whilst rubbing her with his head. He wraps his tail closely around the female and copulation takes place, the female then departs and searches for a nesting site (2). The grass snake is Britain's only egg laying snake (3); eggs are laid in compost or manure heaps, where the rotting vegetation creates warm conditions (2). Development of the leathery white eggs depends on the temperature, but hatching usually occurs 6-8 weeks after egg-laying. The hatchling snakes escape from the eggs by chipping at the shell with an egg tooth, which is lost shortly after hatching. Males become mature at 3 years of age, but females do not begin to breed until they reach their fourth or fifth year. After reaching maturity, males shed their skin twice a year, whereas females slough their skin once a year just before egg-laying. Grass snakes can live for up to 15 years (2).

The grass snake is an active predator of frogs, toads and newts, although fish, small mammals and young birds may also be taken. Prey is grabbed, then swallowed alive. This snake is a good swimmer, and is able to stay submerged for over half an hour (2). This species is predated upon by badgers, foxes, domestic cats, hedgehogs and a number of birds; the snakes rely on their wariness for protection but often 'play dead' when threatened, which may dissuade certain predators from killing them. When caught, they hiss loudly, release pungent and foul-smelling substances from the anal gland, and frequently strike with the head, although they do not bite (2).