The
Grass Snake (
Natrix natrix), sometimes called the
Ringed Snake or
Water Snake is a
European non-
venomous snake. It is often found near water and feeds almost exclusively on amphibians.
Etymology
The name
natrix is probably derived from the
Latin nare or
natare "to swim".
Description
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. In
Great Britain the Grass Snake is the largest reptile, reaching up to total length, though such large specimens are rare. Females are considerably larger than males, typically reaching a size of when fully grown. Males are approximately shorter and significantly smaller in girth. Weight is about .
Since the colour of its collar is often pale yellow to white in the Balkans region, the name for this snake in Serbian/Croatian language is
belouška/bjelouška, which means "white-eared snake".
Distribution
This species is one of only three snakes to occur in
Great Britain, and is distributed throughout lowland areas of
England and
Wales; it is almost absent from
Scotland and is not found in
Ireland, which has no native snakes. It is widely distributed in mainland Europe, ranging from mid
Scandinavia to southern
Italy. It is also found in north-western Africa. British Grass Snakes belong to the subspecies
N. n. helvetica, but experts differ on the number of
subspecies.
Ecology
Feeding
They prey almost entirely on
amphibians, especially the
common toad and the
common frog, although they may also occasionally eat mammals and fish. 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 the
Jacobson's organ). They consume prey live without using constriction.
Habitat
Grass Snakes are strong swimmers and may be found close to fresh water, although there is evidence that individual snakes often do not make use of water bodies 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.
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 2 weeks later in April or earlier if environmental temperatures are favourable. The leathery-skinned eggs are laid in batches of 8–40 in June to July and hatch after about 10 weeks. To survive and hatch the eggs require a temperature of at least , but preferably , with high humidity. Rotting
vegetation such as
compost heaps are preferred locations. The young are about long when they hatch and are immediately independent.
Migration
After breeding in summer, snakes tend to hunt and may range widely during this time, moving up to several hundred metres in a day. They may also perform an aggressive display in defence, hissing and striking without actually opening the mouth. They rarely bite in defence. It is claimed that they may also secrete blood from the mouth and nose whilst playing dead.
Protection and threats
The species has various predator species, including
corvids,
storks,
owls and perhaps other birds of prey,
foxes and the domestic
cat. In England, grass snakes are protected under the Wildlife and Countryside Act 1981 and cannot be harmed or traded without a licence, although they may legally be captured and kept in captivity.
Two of the subspecies are considered critically endangered: N. n. cetti (Sardinian Grass Snake) and N. n. schweizeri. In 2007, the Grass Snake was included on the updated UK Biodiversity Action Plan as a species in need of conservation and greater protection.
Gallery
References
External links
Amphibians and Reptiles of Europe
Reptiles and Amphibians of the UK
BBC Nature
Category:Colubrids
Category:Reptiles of Europe
Category:Reptiles of China
Category:Fauna of Finland
Category:Fauna of the United Kingdom
