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. Subspecies 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. Description 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 or more in length. Distribution 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. Ecology Feeding Grass snakes mainly prey 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 the water, using sight and sense of smell (using Jacobson's organ). They consume prey live without using constriction. Habitat 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