Grass snake

The grass snake (Natrix natrix), sometimes called the ringed snake or water snake, is a Eurasian non-venomous 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. Many subspecies are recognized, including: Natrix natrix helvetica (Lacépède, 1789) was formerly treated as a subspecies, but following genetic analysis it was recognised in August 2017 as a separate species, Natrix helvetica, the barred grass snake. Four other subspecies were transferred from N. natrix to N. helvetica, becoming N. helvetica cettii, N. helvetica corsa, N. helvetica lanzai and N. helvetica sicula. The grass snake is typically dark green or brown in colour with a characteristic yellow 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. Weight is about 240 g (8 oz). 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. British grass snakes were thought to belong to the subspecies N. n. helvetica, though this is now recognised as a separate species. This species was considered to be one of only three snakes to occur in Great Britain, but the grass snakes in Great Britain have now been reidentified as barred grass snake Natrix helvetica, any records of N. natrix in Britain are now considered to have originated from imported specimens. Grass snakes prey mainly on amphibians, especially the common toad and the common frog, although they may also occasionally eat ants and larvae. Captive snakes have been observed taking earthworms offered by hand, but dead prey items are never taken. The snake will search actively for prey, often on the edges of water, using sight and sense of smell (using Jacobson's organ). They consume prey live without using constriction. Grass snakes are strong swimmers and may be found close to fresh water, although there is evidence individual snakes often do not need bodies of water throughout the entire season.