Grass Snake

Durham Priority Species
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Grass Snake Action Plan

Priority Species: Grass Snake

1. Maintain and enhance populations of native grass snakes in the Durham BAP area
2. Increase the available area of potential grass snake habitat and to ensure that existing habitat is managed appropriately for grass snakes
3. Develop our knowledge of the distribution and ecology of grass snakes in the Durham BAP area
4. Increase awareness and understanding of grass snakes and their habitat requirements

Vision Statement: For grass snake to be more common in the Derwent and Wear Valleys by 2015. For consideration to be given to expansion or re-introduction to other river systems by 2020.

Target Type Unit Value
1. To extend the range of grass snake in the DBAP area expand occupied km squares 15

The grass snake is the largest native reptile, and the only snake in Britain which lays eggs. It is most frequently associated with water. River valleys, marshes, damp meadows, and around still waters such as ponds and reservoirs are all potential grass snake areas. Grass snakes also use drier habitats, including open woodland, rough grassland, heath and low intensity farmland.

Grass snakes emerge from hibernation around April or when the temperature is high enough and, after mating, females lay clutches of, typically, between 10 and 25 pale, white leathery eggs in a warm environment such as a compost heap or pile of rotting logs. The young hatch between August and October.

Grass snakes feed primarily and overwhelmingly on amphibians. But they will also take small mammals, birds and fish.

As temperatures drop, grass snakes will seek hibernation sites, such as rubble piles and mammal burrows providing frost, flood and predator-free accommodation.

Local status

The most northerly sites for grass snakes in the UK are scattered across Northumberland, Durham and Cumbria. In the Durham BAP area, historic distribution has related to the river corridors of the Derwent and the Wear.

In recent years the only confirmed records have come from the Derwent, although there are recent unconfirmed sightings from around Wolsingham on the Wear. They are, therefore, very rare in Durham, and probably declining, although it is possible that they are also under-recorded.


  • Habitat loss and modification
    Grass snakes range over large areas, so habitat or range fragmentation can be a particular problem.  Built development, roads or agricultural intensification can all lead to loss of habitat in good grass snake areas.Shading from developing woodland is also a problem at the one known site at Gibside.
  • Disturbance
    Increasing visitor pressure it the one known site at Gibside is a potential threat to Grass Snake as it limits opportunities for feeding and basking.
  • Loss of egg laying sites
    Modern flood control techniques mean that there is much less debris left around riverbanks after flooding. Outdoor manure heaps on farms are now less common, with reduced livestock numbers, and turned over too quickly. Also manure now tends to be stored in inaccessible tanks. Fewer gardeners use accessible compost heaps.
  • Poor knowledge of distribution
    Grass snake sites may be destroyed unknowingly if there is insufficient data available to developers and ecologists.