It’s been an exciting week in the world of herpetology as new evidence suggests we might have a fourth snake species in the UK.
But then you read further and begin to wonder what on Earth is happening. In trying to keep this simple and interesting I’ll use the explanation given by Rob Ward below. This has been widely shared on social media so you may have already come across it.
Focus only on the grass snake – Natrix natrix. This species covered North Africa, up and across through Western, Central and Eastern Europe and further east in to Russia. At this point Natrix natrix was thought to contain about 14 subspecies
( see this paper http://onlinelibrary.wiley.com/d…/10.1111/zsc.12018/abstract).
Now at this point I’ll focus only on the subspecies in the west and centre of Europe. Natrix natrix helvetica is the subspecies of grass snake in Britain, France, small parts of Germany, Belgium, Northern Italy, Switzerland and a little in to some other countries. Roughly speaking though, the Rhine in Germany is where it meets another subspecies – Natrix natrix natrix which covers most of central and northern Europe. To the south of Natrix natrix natrix is Natrix natrix persa which extends down in to the Balkans (but the new study suggests that Natrix natrix natrix then appears below that also…confusing). The new paper out yesterday suggests that there is a lot of overlap and mixing between Natrix natrix natrix and Natrix natrix persa, so they are left as subspecies. There is probably more to be done on this.
We had Natrix natrix helvetica. Now we have Natrix helvetica helvetica. Nothing extra – still 3 snake species in Britain. The divergence between this and the other species it was previously a part of occurred approximately 7.3–8.2 million years ago. There may be some confusion as the paper mentions some non-native grass snakes in Britain that most likely arrived through the pet trade.
The original article is open access and can be found here: https://www.nature.com/articles/s41598-017-07847-9
So in summing up we still have the one but as suggested above the striped N.n persa has established itself due to being introduced via the pet trade.
For a cheeky look at these Italian imports
Interesting to note that another Mediterranean snake the Aesculapian snake has established long term breeding populations in London and North Wales. Both populations believed to be the result of zoo escapes . North wales Mountain Zoo in Colwyn bought some in back in the 60’s only to have them escape. Years later juveniles were seen basking in the grounds of the zoo. Regents Park canal next to the London Zoo is the place to spot them in ‘the big smoke.’ I wonder how long they have to be here before being classed as native? Also what is it about our climate that allows these Italian species to thrive?