The Snake With A New Identity

The barred grass snake (Natrix helvetica) is one of the three snake species present in the UK. Once thought to be a sub-species of the common grass snake (Natrix natrix), the barred grass snake gained it full species status in 2017 after research into the genetic lineage of grass snakes across Europe indicated that the UK populations were actually a separate species.

Look at that tongue! Photo by: Anne Marie Kalus

Distribution & Habitat

The barred grass snake is found commonly throughout England; however, their distribution is becoming increasingly patchy as populations decline. They are uncommon in Scotland, Northern Ireland, Ilse of Scilly, the Channel Islands and large areas of Wales, as well as the counties of Wiltshire, Cornwall and Devon, where the habitat is not conducive to the grass snake's life cycle. The distribution of the barred grass snake extends across the palearctic region from Russia to the UK and from Spain and Greece in the south, up to Sweden.

The barred grass snake favours wetland habitats, such as ponds, lakes and rivers. Microhabitats such as, heavily vegetated banks, ditches, and hedges surrounding wetland areas provide the barred grass snake with valuable refuge from predators. These microhabitats are essential for the barred grass snake's existence within a habitat and without them, the habitat is no long suitable for barred grass snake populations. During mid-summer (June/July), once their main prey (amphibians) has migrated away from the ponds, grass snakes will also move away from wetland habitats and favour drier habitats, such as woodland edges, grasslands and gardens.

Barred Grass Snakes in Gardens

Barred grass snakes love gardens, especially gardens with ponds. Compost heaps make excellent hibernacula and nesting sites for barred grass snakes. Like most snake species, the barred grass snake does not have fangs or venom to defend itself, and will rarely attack. Consequently, the barred grass snake is completely harmless to people, so do not worry if you encounter one. If you do have a garden in your garden, the best thing to do is to admire its beauty from afar and leave it alone.

A barred boi vibin' in a garden pond. Photo by: Jan Wilson

Let's play a game of Find The Grass Snake. Photo by: Fred Holmes

Identification

The barred grass snake can be easily identified by its black and yellow collar, which typically forms a ring at the base of the snake's head. Although colour can vary, the barred grass snake is typically olive green/brown with black vertical bars along the flanks. These bars are interspersed by parallel rows of black markings (such as dots and dashes). These markings vary in size and shape, depending on the individual snake. The underside of the barred grass snake is buff, cream or white in colour with a black chequered pattern. The underside markings of the barred grass snake are unique to the individual, like a fingerprint! The face also features black markings and bars below the eye, unique to the individual. Very rarely, melanistic (completely black), off white/buff, and fully green colour variations have been sighted. Female barred grass snakes grow to 1.2 meters in length, which some individuals reaching 2 meters in length. Males are smaller than females, reaching 60cm in length. Males and females can further be distinguished by their head shape, with females having a more pronounced triangular head shape and deeper set eyes. Males typically have a more slender head and eye that protrude beyond the line of the face and jaw. Another distinguishing characteristic between males and female is the number of ocular scales (the scales surrounding the eyes), where females typically have 2 ocular scales and males have 3. Juvenile barred grass snakes look much like their adult counterparts, but much smaller.

There are 2 other species of snake in the UK, however the barred grass snake can be easily distinguished by its black and yellow collar. The adder has a distinct zig zag pattern down its spine, and the smooth snake, which is very rare and only found in a few Southern counties, has a plainer appearance. Neither of these species possess the same distinct collar marking of the barred grass snake. Juveniles of the Aesculapian snake, invasive to the UK and found in Colwyn in North Wales and the Regent's Canal in London, have sometimes been mistaken for barred grass snakes as they have a light collar, however they lack the distinct yellow colouration of the collar seen in barred grass snakes. The slow worm, which is in fact a lizard, is sometimes mistaken for a snake, however they can be distinguished by looking at the head. Slow worms have no distinct neck and have eyelids, which snakes lack. In addition to this, slow worms also do not have the black and yellow collar commonly associated with grass snake species.

Look at this stylish fella with his beautiful collar. Photo by: Ben Limburn

Eyeliner to make all the e-girls jealous. Photo by: Tony Phelps

Diet

The barred grass snake has a very sophisticated palette, savouring the flavours of small fish, newts, frogs, toads, slow worms, young chicks of waterfowl, and small mammals. Barred grass snakes have a seasonal diet that varies depending on the time of year. From March until mid-May, barred grass snakes will typically predate on small fish, which spawn during these months. From May until late June/early July, barred grass snakes will snack on newts. After July, barred grass snakes will disperse from ponds into woodland and grassland, where they will predate on frogs and toads, which occupy these habitats after breeding in the Spring. Juvenile barred grass snakes predate on young fish, tadpoles, froglets and toadlets, and worms.

Having a bad day? At least you're not this slow worm. Photo by: Jukka-Pekka Tikkanen

Predators

Barred grass snakes are predated by domestic animals, such as cats and dogs, birds of prey, herons, pheasants, corvid, mustelids, hedgehogs, foxes and even terrapins. Juveniles are very vulnerable to predation, especially by cats, pheasants and blackbirds. Nevertheless, the barred grass snake does have some tricks up its metaphorical sleeves to avoid becoming someone's next meal. Its main defence is the secretion of a pungent smelling liquid, called musk, which is expelled from its anal glands and is mixed with faecal material from the cloaca. This liquid truly smells like the worst things imaginable and is enough to put anyone off their meal. On the off chance that a predator finds this stench appetising, the barred grass snake will resort to plan B, which involves playing dead. If only escaping our problems was this easy. The barred grass snake is an expert at mimicking death and will invert itself, so the underside is visible to the attacker and the snake will keep its mouth open with its tongue flopping out to one side.

Someone hand this snake an oscar. Photo by: ARC Trust

Lifestyle & Reproduction

Barred grass snakes are a diurnal species, meaning they are active during the day. Their favourite hiding spots include moss covered undergrowth, under the over-hangs and banks of heavily vegetated water bodies, and in rotten stumps and hollowed out logs. Like many reptiles, barred grass snakes will shed their skin as they grow. Barred grass snakes will shed their skins in groups ever 6-10 weeks. When a snake is due to shed its skin, its colouration goes dull and their eyes go cloudy. It is still unknown as to why barred grass snake shed their skins together.

Barred grass snakes are ectotherms and regulate their body temperature using external sources of heat, such as the sun. In late Autumn (October/November), barred grass snakes will go into brumation- a hibernation like state of inactivity. Rabbit burrows, root systems, under buildings, hay stores, and compost heaps, are excellent hibernacula for snakes. Suitable hibernacula will have a higher temperature than the surrounding environment. Compost heaps are excellent hibernacula because the decaying food waste produces heat, which keeps snakes warm!

Barred grass snakes will emerge from brumation in the Spring (March/April). It is during this time that they begin their hunt for a mate. The snakes will congregate in large numbers, forming mating balls where there could be up to 8 males for just 1 to 2 females. Mating can last up to 2 hours. Mating balls form when a female basks in the sun, with an open cloaca, which attracts the males nearby. A ball of writhing noodle bodies will form, tightly intertwined, and the lucky male is the one that is first to successfully align their vents. It's not very romantic, but whatever floats your boat.

Barred grass snakes are the only egg-laying snakes in Switzerland, typically laying eggs in June and July. Clutch size is correlated with the size of the female, with young females laying between 7-15 eggs and mature females laying roughly 25 eggs. The eggs are incubated in rotting vegetation, such as compost heaps, for 70 days. Weather greatly impacts the incubation period, with colder temperatures causing longer incubations and warmer temperatures causing short incubations. The temperature and incubation period also impact the sex ratio of hatchlings, with colder temperatures and longer incubations resulting in more female offspring, and warmer temperatures and short incubations resulting in more male offspring. Clutches have a hatching success rate of 45% - 75%, with only 50% of these hatchlings surviving to breeding age. In the late summer juveniles will hatch and immediately begin to hunt before entering brumation. The first brumation period causes the greatest losses in juvenile barred grass snakes, as they lack experience in hunting and finding suitable hibernacula. Upon hatching, juveniles measure between 14.8cm and 15cm in length, and reach between 21cm to 22cm after one year. Males will become sexually mature before they reach 30cm in length.

Oddles of baby noodles. Photo by: Chris Gleed-Owen

Threats & Conservation

With increased urbanisation and human activities, rural countryside is being disturbed which impacts for the biodiversity. Migration routes of the barred grass snake are now interrupted by suburban developments, which has consequently led to a decline in grass snake populations over the past decade. Habitat fragmentation and degradation, and agricultural intensification have further contributed to the declines of this species, in addition to the decline in wetland habitats which support the barred grass snakes' main food source. The declining numbers of barred grass snake are a cause for concern in the UK, with there being an estimate of as low as 180,000 barred snakes left in the UK.

The barred grass snake is protected by the Wildlife and Countryside Act 1981, making it an offense to sell, kill or injure any barred grass snake. However, there is no protection for their specialised habitat requirements by any SSIs or SACs.

How You Can Help

With a little planning, you can create an impactful garden for local biodiversity, including barred grass snakes. Here are some ways you can help!

1) Walk the area of your garden before mowing the lawn. This will allow any critters to disperse and seek shelter. This is especially important on colder days, when reptiles are more sluggish and cannot move as fast.

2) Leave wooden boards, roofing felt or corrugated iron sheets in your garden. These are excellent refuge sites for barred grass snakes and other reptiles. The corrugated iron also provides excellent basking sites, as the mental will conduct the sun's heat.

3) Log piles placed in the sun, rock piles, banks with crevices, south-facing areas close to dense vegetation all provide refuge and a food source for snakes

4) Create a mosaic of different habitat types

5) Ensure there is a point of entry to your garden at ground level

6) Build a pond. This will encourage the barred grass snakes favourite food (amphibians) into your garden, and in turn will entice the grass snakes. Leaving areas of long grass leading towards your pond will provide extra shelter for snakes. Avoid using netting over your pond and vegetable patches, as snakes often get ensnared in the mesh and die. If you still want to use a netting, choose a netting made of a rigid material with a mesh size of at least 4cm (1.5 inches).

7) Build a compost heap. Compost heaps provide excellent nesting sites and hibernacula for grass snakes. When building a compost heap, make it as large as possible and place it in a sunny area of your garden, close to a hedge or dense vegetation. Fill your compost heap with kitchen food waste (but not meat or bones), grass cuttings, dead leaves, shredded paper, garden waste etc. and create layers with nitrogen rich materials (green material) and carbon rich materials (wood and paper etc.). Make sure there easy access to the heap for reptiles, so do not fully seal your heap. DO NOT turn your heap between mid-June and late-September as there may be eggs in your heap. When you do turn your compost heap, do so very carefully as there maybe animals hiding inside.

8) Don't have a cat. Sorry cat people, but cats and snakes are not a great mix. Cats are one of the greatest predators of reptiles. If you have a cat, it's unlikely you will get many reptiles in your garden.

If you are passionate about barred grass snakes and conservation, and wish to get involved, you can volunteer with ARC, ARG and the Wildlife Trusts to assist with their conservation projects. Check out the links below to learn more:

Volunteer with ARC: https://www.arc-trust.org/Listing/Category/volunteer

Find your local ARG to volunteer with: https://www.arguk.org/get-involved/local-groups

Volunteer with the Wildlife Trust: https://www.wildlifetrusts.org/closer-to-nature/volunteer

Become a member of the Wildlife Trust: https://www.wildlifetrusts.org/join