Grass snakes (Natrix natrix) are perhaps the most frequently encountered snake in England and are often mistaken for adders. Grass snakes are completely harmless and very rarely bite. If handled however, they will feign death and release a very unpleasant secretion from their vent. They will also often vomit their last meal in order to escape quickly.

Identification
Grass snakes are usually olive green, but brown or grey specimens can be found. There are light spots or bars on the flanks. The grass snake is a much larger and usually more slender snake than the adder. Female grass snakes grow to 100cm and males to 80cm on average, although females have been recorded up to 180cm. The grass snake has a distinctive yellow and black neck collar and a round pupil. Adders have a vertical pupil.

Male grass snakes are more slender than the female and have a proportionally longer tail than the female. Counting the number of sub-caudal scales is a more accurate method to sex this species. Males have usually 63 or greater, while females usually have 62 or fewer.

Ecology
Grass snakes feed on amphibians, fish and nestling birds, with toads being a particular favourite. Grass snakes are often associated with water and are frequently seen swimming. They can be found in woods, parks, commons, farmland, golf courses and embankments. They like to bask along south facing woodland margins or hedgerows close to dense cover such as brambles. Grass snakes lay eggs in compost or manure heaps during April and May.

Grass snakes in Buckinghamshire
The grass snake is perhaps Buckinghamshire's most common reptile, and is a common sight along river banks in the summer. They are also the most likely reptile to appear in your garden. Although they eat amphibians, grass snakes should be encouraged, because they remove the weak or sick individuals from the amphibian population.

Protection
The grass snake is protected from killing, injury or trade under the Wildlife and Countryside Act 1981.