Surrey Amphibian and Reptile Group (SARG) 

Smooth Snake

  

Nomenclature

Common name:  smooth snake 
Taxonomy:  Coronella austriaca austriaca (Laurenti, 1768)
Other Names:  Neidr fraigh (Welsh)

Introduction

A rare, but beautiful male Smooth snake, held to demonstrate size.

The Smooth snake is the United Kingdom's rarest native reptile; it is totally harmless to man.

In the UK, the Smooth snake is a specialist of heathland, and native populations can be found only in the south of England; in the counties of Dorset, Hampshire, Surrey and West Sussex.

Like most snakes, the Smooth snake will eat almost anything that it can catch and swallow, however; they are mostly associated with a reptillian diet.

Smooth snakes grow to a length of about 60-70cm (exceptionally up to 80cm), and appear slimmer than our other native snakes.

The Smooth snake is so named because it lacks the central keels, or ridges on its scales, unlike our native Adder and Grass snake. This adaptation means that it is not as swift as our other snakes, but is well suited to navigating dense vegetation. Due to this name, the very smooth Slow worm is often mis-reported as being a Smooth snake.

Exceptional individuals have reached an age of almost 30 years in the wild.

Although usually considered mute, Smooth snakes can emit a quiet short hiss when stressed, which is usually associated with a strike or sudden jerk of the forebody. They do not emit prolongued warning hisses like the Adder and Grass snake.


Identification

An adult Smooth snake, coiled, as seen when lifting refugia.

The Smooth snake is usually of a matt colouration; usually a dark grey or dull brown, although brick-red specimens are not uncommon.

The dark, almost black dorsal markings are not immediately apparent, and are arranged along the back, from neck to tail, as pairs of dots, bars or dashed lines. There is usually a second pair of lines, one of each running along the flanks of the body, although these are frequently even less obvious than the dorsal markings.

The top of the head always features a large dark heart-shaped marking, which is sometimes described as a 'butterfly'.

There is a characteristic dark line on the side of the head, that runs across the eye. Unlike the venomous Adder, the Smooth snake has round pupils.


Morphology


Sexual Dimorphism

The best way to determine the gender of a Smooth snake, is to examine the shape and length of the tail. As with all British snakes, the male's tail is both longer (54-65 subcaudal scale pairs), and tapers more gently than that of the female (44-56 subcaudal scale pairs). Male tail length accounts for around 20% of the total body length, whilst the female's tail accounts for about 16%.

General rules of thumb do apply for differentiating the sexes: Usually, the males are a brown colour, with the females being grey. Another useful rule is to examine the throat colour. Males tend to have an orange hue to the throat, whilst the throat of the female tends to be cream. Throat colour differentiation is accurate in about 80% of cases.

Adult female Smooth snakes tend to be larger than the males, with females weighing up to 150 grammes when gravid, or 100 grammes when non-reproducing, and males weighing up to 90 grammes. Although females are of a slightly heavier build, they are no longer than males on average.

Adult female Smooth snake - note the cream throat and grey colouration.
Adult female Smooth snake - note the cream throat and grey colouration.
Adult Male Smooth snake - note the orange throat and brown colouration.
Adult Male Smooth snake - note the orange throat and brown colouration.

Could be mistaken for

The smooth snake

The smooth snake could be mistaken for any of the snake species found in the UK, however it most resembles the adder.

A grass snake (left) and a smooth snake (right) for comparison.
A grass snake (left) and a smooth snake (right) for comparison.

Distribution

Global distribution for smooth snake © http://seh-herpetology.org

The Smooth snake's natural range is mainland Western and Southern Europe. It is present in Scandinavia, Western Europe, South to the Mediterranean and as far East at European Turkey. In the British Isles, it is found only in Southern England, within the counties of Dorset, Hampshire, Surrey and West Sussex. A recent introduction in 2009 increased this range to include Devon. Historically, the snake was found in Berkshire and Wiltshire. There are less reliable historic records including Buckinghamshire, Kent, Somerset and East Sussex.

In Surrey, there are many healthy populations in the West of the county, on heathland surrounding Farnham. Some sites have original native populations (such as Ash Ranges and Crooksbury), whilst other heaths feature re-introduced animals from Dorset.

It is probable that not all Surrey Smooth snake populations have been discovered, as it has been shown that three years of focused survey effort is sometimes required to determine their presence, due to their secretive and elusive nature. Targeted survey effort by SARG in coordination with the ARC is underway to determine their presence at a number of probable sites, and to confirm absence at sites targeted for re-introductions.

UK distribution for smooth snake © NBN
UK distribution for smooth snake © NBN
Surrey distribution for smooth snake © SARG
Surrey distribution for smooth snake © SARG

Habitat

Deep moss within mature heather is ideal habitat for Surrey smooth snakes.

In the UK, the Smooth snake is thought of as a heathland specialist, although it will happily hunt in grassland habitats. The stronghold of the British animals is the heathlands of Dorset, although many of the heaths along the Surrey/Hampshire borders also support strong populations.

In Surrey, the Smooth snake shows a marked preference for dry lowland heathland, comprising mosaic mature heather with a deep (~30cm) moss sub-structure to the vegetative layer.

Mosaic mature heather with a mix of gorse and sparse trees below a south-facing bank.
Mosaic mature heather with a mix of gorse and sparse trees below a south-facing bank.

Activity

A rare sighting of a Smooth snake openly basking on a bank. © Steve Langham

Smooth snakes are diurnal, but extremely secretive. Very few sightings of this elusive snake are in the open. It is most oftenly encountered when lifting refugia. They rarely bask openly, prefering to bask whilst partly entwined in vegetation, particularly heather. Their superb camoulflage makes them extremely difficult to spot.

Although the Smooth snake is nationally scarce, where they do occur, and the habitat is suitable, they can establish strong populations with high numbers of animals.

There has been long discussion as to the range of an individual Smooth snake. The same snake can be found under the same refugia for decades, leading to the belief that they move only short distances. Recent research by SARG has shown that although a snake may use the same refuge as a 'home base', the animals may travel a few hundred metres. Snake identification by photo has shown that although recapture under the same refuge is the norm, when found in the open, the snake may have travelled some distance.

The true range of the animal will always be difficult to determine, as recapture rates are low, and most Surrey sites are not large, due to fragmentation of their habitat.


Food

The pygmy shrew is a prey item for larger smooth snakes.

In common with most British snakes, the smooth snake will prey upon any living vertebrate that it can catch and swallow. It is most often thought of as a reptile specialist, predating common lizards, slow worms and even the endangered sand lizard. Smooth snakes will also eat other snakes, and can predate young adders of up to 30cm in length. They will also take small rodents and fledgling birds, especially from nests close to ground level.

The smooth snake is initially an ambush predator, then stalks its prey cautiously upon detection. On striking, the snake grasps its prey using its row of sharp and backwards-curved teeth. The snake will then coil around its prey, in a similar manner to constricting snakes. The smooth snake is not a true constrictor (although it may use constriction to subdue larger prey items, such as mature slow worms), but uses this coiling mechanism to subdue its prey, and to orientate it head first into its mouth. The snake takes its prey by overpowering its food, and often swallows it whilst alive.

Whilst lizard prey is the mainstay of both sexes, females tend to diversify at a younger age, taking mammals and other snakes. There is a tendency for females to eat less frequently, but to predate larger prey items. Smooth snakes can be cannibalistic, eating smaller specimens of their own species.

Young snakes appear to consume mainly reptilian prey, predominantly juvenile common lizards. As the snake grows, more small mammals become part of the main diet, particularly shrews and voles. DNA analysis has detected traces of earthworms in smooth snake faeces, however this is thought to be a result of secondary predation (the prey had eaten earthworms).

Adult and juvenile common lizards are the primary diet of young smooth snakes.
Adult and juvenile common lizards are the primary diet of young smooth snakes.
Juvenile adder of up to 30cm can be predated by smooth snakes
Juvenile adder of up to 30cm can be predated by smooth snakes
Slow worms are a mainstay of smooth snake diet.
Slow worms are a mainstay of smooth snake diet.

Predators

The domestic cat can a predator of smooth snakes where they occur close to human habitation.

The main natural predators of the Smooth snake are birds, including pheasants, crows and birds of prey.

Mammalian threats come in the form of Foxes, Badgers and Mustalids (Weasels).

The Smooth snake does not exhibit the wide range of defence mechanisms present in the Grass snake, but relies heavily on its superb camouflage. When caught and restrained, the smooth snake will bite readily, but as it is non-venomous, this is of limited deterrent value.

Occasionally the smooth snake will emit an odorous discharge from its vent, similar to a grass snake, however the pungent effect is far less than that of the grass snake.

Pheasant
Pheasant
Buzzard © Marek Szczepanek (GNU)
Buzzard © Marek Szczepanek (GNU)
Polecat (Mustalids)
Polecat (Mustalids)

Shelter

This Smooth snake was seen in a Sand lizard burrow. © Danielle Sweet

The Smooth snake hibernates underground in dry frost-free shelters that are safe from predation. Disused mammal burrows are often used.

Day shelters are probably in deep cover, which correlates well with its prefered habitat of deep vegetative structure. Although, we have one report of a Smooth snake found in a Sand lizard burrow!

In Surrey, all smooth snake sites have a deep moss structure within a heather canopy. This moss structure is believed to offer shelter, a means of thermoregulation and is home to the Smooth snake's preferred prey - the slow worm.


Reproduction

This adult female Smooth snake has recently given birth. It is unusual to find the brood with an adult after a few days of birth. © Jamel Guenioui

Smooth snakes reach sexual maturity at around the age of four years.

In the UK, Smooth snakes usually emerge from hibernation towards the end of March, the males emerging earlier than the females.

Males are aggressive towards rivals, and will actively fight each other. Mating is secretive, usually in deep cover, and occurs in April.

Females do not breed every year, as the condition they lose in generating offspring can take two to three years to recover. As is common with snake species, larger females tend to produce larger litters of young.

The Smooth snake is viviporous, giving birth to between 4 and 15 live young at the end of Summer (August - September).


Juveniles

Smooth snakes give birth to live young, usually in the month of September.

The young share the markings of the adult, but tend to be darker in colouration. Juveniles' heads appear slightly larger in proportion to the body that adults. They are significantly shorter and slimmer than adult snakes, with neonates being around the length and thickness of a pencil.

At birth, young are about 15cm in length and weigh about 3 grammes. The number of young varies between 4 and 14 offspring with a mean of around 5 young.

Juvenile smooth snakes feed mostly on adult and juvenile lizards.

Young smooth snakes suffer predation from the same sources as adults, additionally they have to watch out for other smooth snakes, which can be cannibalistic, especially towards young, small snakes.

After birth, it is usual for the young to stay in a group for a few days, often with the mother. The presence of a male may disperse the young snakes, but they can be frequently found in a basking ball.

Juvenile Smooth snakes have similar markings to adults but tend to be a little darker in shade.
Juvenile Smooth snakes have similar markings to adults but tend to be a little darker in shade.
Juvenile snakes can be seen basking together in a ball © Mary Campling.
Juvenile snakes can be seen basking together in a ball © Mary Campling.

Conservation

Military training at Hankley Common duning WW2. Note the lack of reptile-friendly habitat.

The decline of the smooth snake (90% loss over 100 years) is attributed to loss, deterioration and fragmentation of heathland and dune habitat, scrub and tree incursion, uncontrolled fires and a shortage of suitable breeding sand on heathland sites.

Many of the Surrey heathlands were completely destroyed by fire and vehicles in the 1940s due to training of the Canadian divisions in preparation for the D-day landings and subsequent military operations.


Links


Information

Principal Author(s):Main Illustrator:Edited by:Updated:
Steve LanghamSteve Langham10 Sep 2018