Fingerprinting RSPB Arne’s Smooth Snakes! By Chris Baker
The line of double dots down a smooth snake’s back is like a fingerprint, an identification fail-safe with each pattern, unique to an individual animal. All smooth snakes that have been found during surveys at RSPB Arne have had their lines of double dots photographed – a collection of reptilian kind-of mug shots, if you like.
Rob Farrington, the RSPB’s Visitor Experience Manager in Dorset, said: “We can see if we have found the snake before, when we found it, where we found it and how far it has moved. Having these diagnostic marks means you can build up a picture about them as individuals, although it’s only a little picture because reptiles are difficult to know too much about.”
Five of the snakes – Britain’s rarest reptile, although the most common snake found at RSPB Arne – were discovered during a survey conducted with the BBC prior to Autumnwatch. Three of those had been found before, two were debutantes.
Those tell-tale double dots showed one of the snakes that had been previously recorded, had only moved 50 yards; one of the newly found reptiles was a youngster, and records such as this can be extremely useful when monitoring these long-lived animals.
Rob said: “If they are younger the marks tend to be clear, and if they have just shed their skin it’s fairly easy, but as they get older it becomes more difficult. Some are vastly different, some are similar, but on the whole it’s relatively easy, easier than looking at a human fingerprint.”
Unusually, at RSPB Arne smooth snakes outnumber adders. It could be they are simply out competing their better known relative, adders are not noted as heath dwellers, or it could be that smooth snakes are eating them – Coronella austriaca, to give its scientific name, likes to feed on reptiles, which includes eating each other.
The secretive animal rarely basks in the open, and when they do they are often found entwined among the stems of heather, their superb camouflage making them almost invisible.
They are about the same size as an adder, although their bodies look noticeably thinner, and get their name from their flat scales which feel smooth to the touch; adders and grass snakes, to complete the trio of native snakes, have a ridge, or keel, on each scale. The dark, heart-shape mark on the smooth snake’s head is almost always present; the adder’s is a dark V-shape, from which the alternative name viper derives.
The snake only survives on lowland heath, such as that found at RSPB Arne, a habitat has declined by more than 80 per cent in the last 100 years and it is now largely confined to heaths in Dorset, Surrey and Hampshire.
The survey mentioned above, which turned up the five smooth snakes, also found two adders, two grass snakes, two slow worms, one sand lizard and a handful of common lizards – RSPB Arne is unusual in having all six of the UK’s native reptiles.
Adders, our only poisonous snake, although its diet of lizards and small rodents means the venom is not very potent, occur in England, Scotland and Wales, but are absent from the Hebrides, Orkney, Shetland and, famously, from Ireland.
Grass snakes occur in England south of the Mersey and lowland Wales. Slow worms, which look like a snake but are in fact a legless lizard, are found everywhere. Common lizards can also be found everywhere in Britain and Ireland, except some Hebridean islands.
Sand lizards are associated with that same largely vanished habitat as smooth snakes and are found in the same places, with an outlying population on sand dunes near Liverpool. There have been a number of re-introductions, largely on sand dunes in an attempt to restore the animal’s historic range. Because of its rarity, like the smooth snake, it is strictly protected and a licence is needed when surveying for them, or doing anything that might harm them.
Nick Moulton, of the Amphibian and Reptile Conservation Trust, said: “At RSPB Arne it is good for both species, when we jointly do surveys we find evidence of these animals a lot quicker than we do at a lot of other sites, which is obviously a very good sign the animals are doing well.”