Barred grass snake

The barred grass snake (Natrix helvetica) is a non-venomous colubrid snake from Western Europe, living in and close to water. It was included within the grass snake species, Natrix natrix, until August 2017, when genetic analysis led to its reclassification as a separate species.

There are currently five subspecies of Natrix helvetica recognized (having been formerly classified as subspecies of N. natrix):

The barred grass snake has a dark grey-green upper body with distinctive black markings in the form of bars running along its sides. Its underside is pale. Like the grass snake, it has a distinctive yellow and black collar around its neck. It can grow to over a metre in length.

The species is found in Great Britain as far north as southern Scotland, and in the Netherlands, western Germany, Switzerland, Italy and France. The nominate subspecies N. h. helvetica has the widest distribution: from Britain to the Pyrenees and the Rhine region.

Barred grass snakes are semi-aquatic and prey mainly on amphibians, especially common toads and common frogs; they also eat fish, some small land mammals and nestling birds, and may occasionally take ants and their larvae. Captive snakes have been observed accepting earthworms offered by hand, but they never take dead prey items. The snake actively searches for prey, often on the edges of the water, using its Jacobson's organ to detect smells and sights. They consume live prey without using constriction.

Barred grass snakes inhabit cooler climates such as those in northern Europe and Great Britain. They live near bodies of water and spend a significant portion of the year hibernating, typically throughout the coldest months. Hibernation periods can begin as early as October, when temperatures start to drop, and may last until April. They either seek shelter to protect themselves from harsh weather conditions or burrow underground to maintain a stable body temperature during hibernation.

Barred grass snakes are strong swimmers and can be found near freshwater. However, there is evidence that individual snakes do not always require bodies of water throughout the entire season.

The preferred habitat appears to be open woodland and "edge" habitats, such as the edges of fields and woodlands. These areas offer adequate refuge while still affording ample opportunity for thermoregulation through basking. Pond edges are also favoured and the relatively high likelihood of observing this elusive species in such areas may explain why they are associated with ponds and water. Barred grass snakes also inhabit gardens and parks in their native range, as well as dry grasslands.