Grass snake

Description

The grass snake (Natrix natrix), sometimes called the ringed snake or water snake, is a Eurasian non-venomous colubrid snake. It is often found near water and feeds almost exclusively on amphibians. The barred grass snake, Natrix helvetica, was split off as a separate species in 2017. The grass snake is typically dark green or brown in colour with a characteristic yellow or whitish collar behind the head, which explains the alternative name ringed snake. The colour may also range from grey to black, with darker colours being more prevalent in colder regions, presumably owing to the thermal benefits of being dark in colour. The underside is whitish with irregular blocks of black, which are useful in recognizing individuals. It can grow to 1 m (3 ft 3 in) or more in length.The grass snake is widely distributed in mainland Europe, ranging from mid Scandinavia to southern Italy. It is also found in the Middle East and northwestern Africa. Grass snakes in Britain were thought to belong to the subspecies N. n. helvetica but have been reclassified as the barred grass snake Natrix helvetica. Any records of N. natrix in Britain are now considered to have originated from imported specimens.Grass snakes are strong swimmers and may be found close to freshwater, although there is evidence individual snakes often do not need bodies of water throughout the entire season. The preferred habitat appears to be open woodland and "edge" habitat, such as field margins and woodland borders, as these may offer adequate refuge while still affording ample opportunity for thermoregulation through basking. Pond edges are also favoured and the relatively high chance of observing this secretive species in such areas may account for their perceived association with ponds and water. Grass snakes, as with most reptiles, are at the mercy of the thermal environment and need to overwinter in areas which are not subject to freezing. Thus, they typically spend the winter underground where the temperature is relatively stable.