Identification
The Grass Snake (Natrix helvetica) is Britain’s longest snake, with large females sometimes reaching up to 1.5m in length! Grass snakes are usually olive green with black bars along the flanks and small black dots on the dorsal side. They can vary in colour with more brown or green colouration possible. They have distinct round pupils in the eyes. At first glance, males and females can be difficult to tell apart. Males have a more distinctive yellow/orange collar behind the head, females are generally larger with a broader head a less distinctive yellow collar. Juveniles look like miniature versions of the adults with similar markings.
Habitat and Feeding
Grass snakes are a lowland species which eat mainly amphibians. Therefore, they require sources of water in order the catch their prey. Interestingly, grass snakes follow a seasonal diet feeding on fish during spring, newts during summer and frogs and toads for the latter months of the year. Juveniles will often feed on tadpoles.
Grass snakes are commonly associated with a range of habitats including heaths and wetlands. Like our other reptiles, grass snakes are also found in open woodland or woodland rides where sunlight is able to penetrate the canopy, enabling them to bask. South facing road and railway embankments are also good places to spot grass snakes. Grass snakes are often found in gardens where they can lay eggs in piles of old grass cuttings or compost heaps.
Distribution
Grass snakes are absent from Ireland and most of Scotland, and very rare in northern England and southern Scotland. Grass snakes are more common across the rest of mainland Britain. Some of the best places to see grass snakes are in the south of England and the Midlands where there is a mixture of dry open habitats and wetlands.
What Do Grass Snakes Get Up to Throughout the Year?
October to March: Grass snakes’ hibernation period is from October to March. During this time, they stay inactive underground in disused mammal burrows, compost heaps, rock piles or in deep leaf/bracken litter. Sometimes grass snakes and adders hibernate in the same hibernation sites. It is important for snakes to find frost free hibernation sites in order to stop them from freezing during the winter. On emerging from hibernation, groups of snakes can be found basking together near hibernation sites.
April to May: Mating begins in April, at which time groups of grass snakes sometimes form a mating ball where several males jostle for position with a single female in order to breed. Usually, the strongest male is successful.
June to July: Females lay their eggs in warm damp places such as rotting vegetation, manure piles or compost heaps. Usually, between 10 to 40 sticky eggs are laid which often stick together in clusters. Often multiple individuals lay eggs in the same locations, with communal incubation sites sometimes containing more than 250 eggs.
August to September: Eggs hatch after two to three months of incubation. The environmental conditions experienced by the eggs can affect the size, behaviour and fitness of the juveniles once they are born. Grass snakes spend the rest of the year fattening up before hibernation.
Are Grass Snakes Dangerous?
Grass snakes are not venomous and pose no risk to humans. However, if handled, grass snakes are likely to emit a disgusting yellowish liquid from an anal gland. They also flail their tail to spread the liquid around. The smell is highly unpleasant and difficult to wash from skin or clothes even after multiple attempts! If that doesn’t put you off, grass snakes often play dead. Going limp and opening their mouths in an attempt to appear distasteful to potential predators.
Population Trends
As with much of our wildlife, populations have declined in recent years. Habitat loss and fragmentation are contributing factors. Many farm ponds have been filled in or lost due to agricultural intensification. Consequently, amphibian populations have also declined, reducing the availability of grass snake food. Grass snakes often have favoured breeding sites which are used year after year, therefore losing an important breeding site can have dire consequences for local wildlife populations.
Check out this video to see Steve Backshall investigating the largest and most widespread species of snake in the UK, the grass snake.
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