Barred Grass Snake

Appearance

The barred grass snake has a dark grey-green upper body with characteristic black barring along the flanks. The underparts are pale. It has a distinctive yellow and black collar around the neck, a feature it shares with the grass snake. It can grow to a length of over a metre.

Naming

There are currently five subspecies of "Natrix helvetica" recognized :
⤷ "N. helvetica helvetica" – most of range
⤷ "N. helvetica cetti" – Sardinia
⤷ "N. helvetica corsa" – Corsica
⤷ "N. helvetica lanzai" – mainland Italy, but not south
⤷ "N. helvetica sicula" – Calabria and Sicily

Distribution

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.

Status

The species has various predator species, including corvids, storks, owls, raptors, common pheasant, foxes, and domestic cat.

In Great Britain, they are protected under the Wildlife and Countryside Act 1981 and cannot be killed, harmed, taken from the wild, kept in captivity or traded without a licence.

In 2007, the grass snake was included on the updated UK Biodiversity Action Plan as a species in need of conservation and greater protection.

Habitat

Barred 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. Barred grass snakes also inhabit gardens and parks in their native range, as well as dry grasslands.

Barred 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.

Reproduction

As spring approaches, the males emerge first and spend much of the day basking in an effort to raise body temperature and thereby metabolism. This may be a tactic to maximise sperm production, as the males mate with the females as soon as they emerge up to two weeks later in April, or earlier if environmental temperatures are favourable. The leathery-skinned eggs are laid in batches of eight to 40 in June to July and hatch after about 10 weeks. To survive and hatch, the eggs require a temperature of at least 21 °C, but preferably 28 °C, with high humidity. Areas of rotting vegetation, such as compost heaps, are preferred locations. The young are about 18 centimetres long when they hatch and are immediately independent.

Food

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 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 smell. They consume prey live without using constriction.

Predators

The species has various predator species, including corvids, storks, owls, raptors, common pheasant, foxes, and domestic cat.

In Great Britain, they are protected under the Wildlife and Countryside Act 1981 and cannot be killed, harmed, taken from the wild, kept in captivity or traded without a licence.

In 2007, the grass snake was included on the updated UK Biodiversity Action Plan as a species in need of conservation and greater protection.

Migration

After breeding in summer, barred grass snakes tend to hunt and may range widely during this time, moving up to several hundred metres in a day. Prey items tend to be large compared to the size of the snake, and this impairs the movement ability of the snake. Snakes which have recently eaten rarely move any significant distance and will stay in one location, basking to optimize their body temperature until the prey item has been digested. Individual snakes may only need two or three significant prey items throughout an entire season.