British Reptiles

This section of the Blog is dedicated to our six (seven if you include Wall Lizard) native British reptiles.  I've always been interested in reptiles, a fascination which came about from getting close to adders and grass snakes on a regular basis while in my teens. The following sections highlight our native snakes and lizards. I'll be adding images and sightings from time to time, so please check back.


Scales
Knowing your scales can help with identification, which can be useful when comparing difficult species. Not quite so important when in the UK but if looking at snakes abroad it may be very helpful to know your frontal from your rostral. Note - vipers have varying degrees of smaller, fragmented head scales and elapids lack a loreal scale:

Scales of the Head (Colubridae)- Click image to enlarge
Snakes regularly shed their skin as they grow, a period known as sloughing. Lead-up to sloughing can often be indicated by 'milky eyes' caused as the new lens forms beneath the old and a fluid forms to help separate the old from the new. Sloughed skins can sometimes be found beneath refuges and can be used to identify which species they belong to.

Conservation


Reptiles are ectothermic, meaning they cannot generate heat through metabolic processes and have to gain their body heat through external sources. This normally involves basking in suitable (and often traditional) spots where they can safely warm themselves in the sun. South facing banks or slopes with rough vegetation and open patches are ideal, allowing escape from predators if disturbed. Much of today's countryside is over managed and as a result too neat and tidy for reptiles. This has led to isolated pockets of suitable habitat, which support small, isolated populations of reptiles - never good from a genetic point of view. This is not the only problem though. Pockets of habitat must also carry enough prey animals to support a population, offer suitable breeding habitat and have suitable places for hibernation as well. This can be quite a tall order and is becoming increasingly difficult to find. Unfortunately reptiles are unable to 'sit it out' until the good times arrive. More often than not the loss of mid-successional habitats simply leads to local extinction. In an ideal world suitable habitats also need to be joined by corridors of similar vegetation allowing populations to disperse in safety and colonise new areas. All six of our reptiles are on the BAP (Biodiversity Action Plan - sections 41 and 42) and are featured on SAPs (Species Action Plans), which outline the steps required to help conserve the species. They are all offered varying degrees of protection under The Wildlife and Countryside Act 1981 (all on Schedule 5 with threatened species also on Schedule 2).

Disturbance is also an issue and is just as difficult to address. At a time when more people than ever are getting in touch with nature and turning to photography as part of their hobby, species disturbance is inevitable. Can it be controlled? Probably not. Educating people of the needs of reptiles and amphibians is one thing but expecting them to stay clear and leave well alone is unrealistic and it would be hypocritical of me to suggest that some people are ok to take photos whilst others should not.  I think even ecological consultants who regularly study populations, taking biometric measurements and in some cases translocation populations, cause as much if not more disturbance than the casual photographer, albeit in the name of science. I've met a number of licenced reptile workers whose knowledge is incredibly poor and it does beg the question: Does having a bit of paper with your name on it make you more qualified to disturb a species? I believe not.

What can we do to help?

Leaving areas of rough grassland whilst maintaining suitable basking areas is a start. Variation within a habitat is crucial but shade from overgrown trees can ruin a once good site. Removal of invasive established trees such as conifer saplings, can greatly help potentially (or formerly) good sites to recover their suitability for reptiles. Rock or log piles (or discarded brushwood) makes for a great shelter and possible hibernation site for most species. Grass snakes need suitable egg laying sites to breed - compost heaps are ideal because they offer moisture and warmth as the vegetation breaks down and this helps to incubate the eggs. The bottom line is sites need to be managed but not over-managed or micro habitats and prey species disappear and reptiles along with it. Habitats often managed for insect and other invertebrate life are usually good for reptiles too.

Native British Snakes


Colubridae


Grass Snake Natix natrix helvetica
The Grass Snake is our most frequently encountered member of the Colubrid family (the only other in the UK is the Smooth Snake) and it is found pretty much throughout the UK in suitable habitat. It likes to be near water (stagnant or slow flowing) where its prey lives (mostly frogs, toads, tadpoles, fish and newts but they will take small fledgings and mammals too). It is equally at home in gardens with ponds offering suitable cover. Compost heaps are a favourite place to lay their eggs because of the warmth given off by the decomposing matter. They are superb swimmers and are able to stay submerged for up to 20 minutes at a time. Grass Snakes are mostly diurnal but also hunt at night. When approached they will try to flee but if cornered they puff themselves up, hiss and usually throw mock strikes at the perpetrator. If that fails they may bite but their small teeth do not cause any major discomfort. They are completely harmless to humans although strictly speaking they do have venom (Duvernoy) glands, just no means of delivering it*. It is thought that the venom is secreted at the back of the throat with the saliva and helps to digest the live prey as they are swallowed. Note the round pupils, unlike vipers (see below).

Grass Snake - showing the forked tongue: Roger Harris
Portrait of the individual above: R. Harris
Grass Snake: Andy Grinter

There are many forms of the Grass snake across Europe (at least 12 varietal forms are known). In the UK we have the form Natrix natrix helvetica, which is also known as the Barred Grass Snake, due to the vertical bars on the flanks of the snake.

Portrait shot of a stunning male: R. Harris
Head scales: clearly showing the parietals, frontal,
supraoculars, prefrontals and nasal scales.
Playing dead after ejecting the contents of its post anal
gland failed to frighten me off.
This male's playing dead too, he's also
about to slought (note the milky eye): R. Harris
Portrait shot
Showing the length of the tongue and the deeply forked
end, which is placed back on the Jacobson's organ on
the roof of the mouth to 'taste' its surroundings.

* a close relative the European Montpellier Snake, has proven to be quite venomous and although it is not considered a danger to humans (it's fangs are situated at the back of the mouth) it could, in theory at least, deliver a potentially venomous bite if it managed to secure its mouth onto a finger or part of the hand and chew to deliver its toxic venom/saliva mix.


Smooth Snake Coronella austriaca.

Definitely one of my favourite snakes (lets face it, we only have three natives to choose from), the Smooth Snake is now a mega rarity and pretty much always difficult to find, even in places where you know it lives. The highest populations are confined to suitable heathland habitats in Dorset, Hampshire and Surrey with smaller numbers in West Sussex and introductions in one or two other places. The Smooth Snake is an almost mythical reptile in Britain. They are members of the widespread Colubrid family (Grass Snake being the other UK representative - see above). They are harmless although larger specimens can draw blood with their small, needle-like teeth. They can reach sizes of around 65-70cm when fully grown and can live for up to 35 years in the wild. Regarded as dietary specialists they are quite partial to lizards (including the rare Sand Lizard) and regularly eat slow worms too. Young adders are occasionally taken but no threat is posed to adults. Smooth snakes are constrictors and will bite to hold their prey before wrapping coils around them to suffocate and subdue them. Prey is then swallowed whole, head first, usually alive. They are truly stunning creatures and if you're ever lucky enough to see one, you'll appreciate just how graceful and elegant they are. Another trait of smooth snakes is the habit of sitting still when spotted, unlike other snakes they don't usually flee but sit tight in the hope you haven't seen them. It's possible to observe them half hidden sitting under vegetation. They rarely bask fully in the open as they can operate at lower body temperatures than our other snake species and don't need to bask right out in the sun. Reptile refuge panels in suitable areas can often be good places to look too. Females tend to be greyer than males (which are often browner or even reddish in colour), more bulky in appearance and have a slightly shorter tail than males. Males often have a buff or orange colouration to the throat as well. The head has a beautiful oval shape from the side caused by the rostral scale at the tip of the snout, which curves up and over to intersect the two internasal scales, a feature which can be seen clearly from above. Melanism is more frequent on the continent than in the UK and the individual shown below is rare indeed...more info on melanism in the UK can be found here (PDF).

Smooth Snake Coronella austriaca:
Male approx 18 inches long.
Dorset, 2016 R. Harris
Smooth Snake Coronella austriaca 
Portrait of the above male: R. Harris
Smooth Snake Coronella austriaca 
Portrait of the above male: R. Harris
Head scale arrangement: R. Harris
Smooth Snake Coronella austriaca: R. Harris
Smooth Snake Coronella austriaca: R. Harris
Smooth Snake Coronella austriaca - portrait: R. Harris
Smooth Snake Coronella austriaca - showing the red tongue: R. Harris
Melanistic adult - incredibly rare,
possibly only the third UK record: R. Harris
Detail of head scales: R. Harris
Showing the amber eye with round pupil: R. Harris
'Balling' to confuse a potential predator. It hides its head
between the body coils to avoid it being bitten.
Smooth Snake: R. Harris
Here the curved rostral scale can be clearly seen
Smooth Snake: R. Harris
Smooth Snake: R. Harris
Portrait shot of the above specimen, April 2014

Viperidae


Adder or Common European Viper or Northern Viper Vipera berus
Adders are our only representative of the True or Old World vipers. As such they are venomous and can deliver a fairly potent cytotoxic venom, which is designed to help kill and speed up the digestion process of their prey. The venom also acts as a haemorrhagic causing the breakdown of the vascular system and results in localised internal bleeding (due to enzymes like phospholipase A2). Common symptoms in humans are abdominal pain, swelling and mild necrosis at the site of the bite, vomiting, diarrhoea and hypotension. Recurring shock is also common amongst adult victims. Other more serious recorded symptoms can include pulmonary edema, generalized plasma leakage, seizures, deep venous thrombosis, compartment syndrome (build up of pressure in the limbs or abdomen), numbness, paraesthesia (tingling/pins and needles) and myocardial infarction (heart attack). There have been rare reports in Europe of neurotoxic symptoms from (V. berus bosniensis) bites resulting in diplopia and dizziness highlighting the variations in venom constituents and potency between different populations. Polyvalent antivenoms are available (Zagreb) but are usually only administered if serious envenomation symptoms are present. These comprise specific antibody fragments that bind with and neutralise Vipera berus venom components, including proteases, lipases and cardiotoxins, aiding their redistribution away from target tissues and subsequent expulsion from the body. Though rarely serious in humans it is advisable to seek medical attention if bitten. The elderly and young children are most at risk from an adverse reaction (anaphylaxis is the most common). Nobody has died from adder bite in the UK since 1975. Indeed the UMR (Untreated Mortality Rate) for V. berus is around 0.5% or roughly 1 in 200 cases. In the last 140 years there have 14 recorded deaths from V. berus envenomations in the UK. Envenomation symptoms can last for up to 48 hours and anyone presenting serious symptoms can expect a hospital stay of 36-48 hours whilst minor bites are usually treated in a single day. Resulting damage from a bite varies considerably from no long lasting physical symptoms to more serious complications - all bites should receive medical attention. I had an aunt who was bitten on the thumb as a young woman and the resulting envenomation left the thumb paralysed for life. Vipera berus produces around 18mg of venom and when delivered intravenously has an LD50 (the lethal dose that kills 50% of animals under laboratory conditions) of 0.55 mg/kg. In his study of 'Adder bites in Britain' for the British Medical Journal,  H. Alistair Reid notes that of the 95 UK victims "Most (75) victims were male, and no fewer than five out of six were bitten on the finger, thumb or hand...In contrast, two - thirds of the 20 female victims were bitten on the foot or ankle. Obviously men have a predilection for picking up snakes not shared by women." He also notes that there are far more deaths from bee and wasp stings than from adder bites.

Adders are usually very distinctive. Note the red eyes and vertical pupil, dark zig-zag pattern down the entire length of the dorsal region and relatively thick, heavy body. Males are generally grey or silvery in background colour with a blacker zig zag pattern whilst females tend to be have a browner base colouration with a brown zig zag. Males can also be distinguished by their slighter build and more contrasting supralabials compared to females - this can also be useful when trying to sex pre-slough males, which often appear brown on emergence from hibernation. Melanism is fairly common in adders and there are several unproven theories as to why this might be, the most likely being that it gives those individuals thermoregulatory advantages in that they can warm up quicker and spend more time hunting than more regularly patterned individuals. Melanism is also found in both Grass and Smooth Snakes (see photos of smooth snake above). In UK females normally give birth biennially.


V.berus, male, I-O-W April 2016: R. Harris
Portrait of the above snake: R.Harris
V.berus, Durlston Country Park, March 2016: R. Harris
Probable male not long out of hibernation - note the
zig-zag pattern is very dark (see female below): R. Harris
Female about to slough her skin. Note the
cloudy appearance of the eye. R. Harris
Typical defence posture.
Portrait shot showing the 'cloudy' eye caused by the
old lens separating from the new one underneath. R. Harris
As above
Showing the typical Old World Viper head scales.
Video of the above snake

Recently emerged female, I-O-W
April 2017: R. Harris

Portrait of female, I-O-W
April 2017: R. Harris


Native British Lizards


Lacertidae


Sand Lizard Lacerta agilis
Our rarest lizard, confined to sandy lowland heaths and sand dunes in Southern England and coastal sand dunes in one or two areas of Northwest England and Wales. Males are bright green, particularly after emerging from hibernation in March/April as they prepare for the breeding season. Females have much less green on them and are generally duller in overall colour. Compared to our common or viviparous  lizard, sand lizards are noticeably chunkier in build and usually larger too - up to around 8 inches in length. They also carry the distinctive 'eye' spots along the flanks. The best time to see them is early morning as they bask in the sunshine to warm up, particularly in the early Spring when the males are the first to emerge from their winter hibernation sites. They eat mostly invertebrates but have been known to eat their own young - more a reaction to eating anything that's small and quick moving that they can catch rather than a food choice though. Rather ironically, sand lizards (our second rarest reptile) are often predated by our rarest native reptile, the Smooth Snake (above). Unlike our Common lizards Sand Lizards seem a little less inclined to scurry away quickly but rather rely initially on their camouflage to prevent them from being seen.

Sand Lizard, male - Dorset 2015: R. Harris
Sand Lizard, male - Dorset 2015: R. Harris
Male Sand Lizard, March 2014: R. Harris
Male Sand Lizard, March 2014: R. Harris
Male Sand Lizard, March 2014
Not so bright, this may be
A non-breeder: R. Harris
Blending with the moss, male Sand Lizard
March 2014: R. Harris
Male Sand Lizard, April 2014: R. Harris

Common or Viviparous Lizard Zootoca vivipara (formerly Lacerta vivipara)
As the name suggests, this is our commonest lizard - frequently disturbed as they sunbathe along the edge of paths. The first sign of their presence is normally a movement as they disappear into the undergrowth. They are renown for using regular basking spots though and if you catch a glimpse of one disappearing, move away, wait 10 minutes and return slowly - there's a good chance it will be back in the same spot. They can be found across a wide variety of habitats from heathland to allotments and gardens and are found, albeit patchily, across the UK. They are diurnal and warm up more quickly than Sand Lizards, as a result they spend less time sitting in the sun. Sexes are very similar although females are usually heavier built and often have a dark vertebral stripe against a paler back.

Common Lizard, male: R. Harris
Common Lizard, male: R. Harris
Common Lizard, male: R. Harris
Common Lizard: Andy Grinter
Common Lizard: Dave Helliar
This is a juvenile, note the dark tail remaining (young are black at birth)
The hint of dark vertebral stripe and dark flanks indicate a female.
Common Lizard: Dave Helliar
Same individual as above
Common Lizard, female: R. Harris

Anguidae


Slow Worm Anguis fragilis

Despite its looks the Slow Worm is not of course a snake (or a worm) but a legless lizard. The main differences between Slow Worms and snakes are that Slow Worms:

1. Have eyelids
2. Will readily shed their tail if miss-handled
3. Don't have a clearly discernible head from the rest of their body
4. They have a fairly broad, flat tongue, which is quite different from a snake.

The Slow Worm is by far our commonest and most widespread reptile in the UK, occupying a wide variety of habitats. However, habitat destruction and degradation has affected Slow Worms in much the same way as other reptiles and in recent years there has been concern for the general decline of the species. They don't tolerate very hot weather well and normally disappear to an underground retreat in such conditions. They feed on small invertebrates including slugs, snails and spiders. Like Grass Snakes, they benefit from compost heaps and can be most frequently found under corrugated refuges. Sexes differ in colouration - females are often darker, coppery brown and frequently have darker flanks and a dark vertebral stripe too. With age, males frequently develop blue spots along the body.


Family group, female top, hatchlings and male lower right.
Unusually this was taken in April, 2014. Young are not normally
born until late summer: R. Harris
Slow Worm, female: R. Harris
Close up of head showing the round pupil
After initially thrashing around for about 30 seconds
they often settle down and become very docile.
Handle gently or they will shed their tail.

Wall Lizard Podarcis muralis

Native to the Channel Islands but introduced at over 50 sites in southern England. Most notably at Ventnor on the Isle-of-Wight, which is home to the largest and oldest population in the country having become established there in 1841. Most colonies consist of the browner form from north western Europe but some, including Ventnor, have animals with closer resemblance to spp nigriventris from NW Italy where the males tend to have much greener backs. Wall Lizards have stouter legs and head compared to vivipara and are, as their name would suggest, agile climbers normally found on wall and rock faces. They can be quite approachable but will dive for cover in basal vegetation or cracks in the wall/rock face if disturbed.

Wall Lizard, Ventnor: R. Harris
Wall Lizard, Ventnor: R. Harris
Wall Lizard, Ventnor: R. Harris
Wall Lizard, Ventnor: R. Harris

Wall Lizards in the UK are often confused with Common (Viviparous) Lizards Zootoca vivipara, particularly in browner individuals, but there are subtle differences which can be easily seen in the comparison photo below including and larger head, stouter legs and longer toes on the Wall Lizard:





As I continue to update this page I hope to add information on our non-native species in the future.

3 comments:

  1. Very interesting article. Enjoyed reading it.

    ReplyDelete
    Replies
    1. Thank you Christopher, glad you enjoyed it.

      Delete
    2. Just noticed you're in the Yukon! One of my favourite places - been up there on three occasions. You are very lucky, what a great place to live.

      Delete