Britain’s non-native herpetofauna

Britain is a unique island in that throughout most of the last glacial maximum most of the landmass was covered by ice – apart from a small portion in the south of England. Ireland on the other hand was completely covered in ice which helps to explain why there are no native species of snakes found there unfortunately it wasn’t St. Patrick’s doing. Recently I had somewhat of an epiphany whilst writing a manuscript for the local nature journal here in Cambridge. The number of non-native reptiles and amphibians found in the UK far outweigh those of native ones. If we go to a verified source such Record Pool (a collaborative project run by the Amphibian and Reptile Conservation Trust and the Amphibian and Reptile Groups UK), we can see that a total of 34 reptile and amphibian species have been recorded. There are 13 native herpetofauna species in the UK, 6 of which are reptiles and 7 of which are amphibians. This means that there are 21 non-native species which have been recorded. That may sound like a lot and it is, but there are a couple of simple explanations as to why there are so many. The first is that for centuries people have tried to seed the UK with numerous non-native animal and plant species to boost those found here. Some of these have been successful and some haven’t. The second reason is linked to the pet trade, sometimes animals escape and sometimes irresponsible owners release their unwanted pets into the wild (despite this being illegal under the 1981 Wildlife and Countryside Act). Non-native species threaten our own by predation, competition, hybridisation and the spread of disease.


A red-eared slider from a population I monitor outside of Cambridge

One of the most easily recognisable non-native reptile species is the red-eared slider (Trachemys scripta elegans). The terrapins were a common pet in the 1990’s after the success of the Teenage Mutant Ninja Turtle franchise. It’s a sad state of affairs as the terrapins themselves are ill-equipped to survive in the colder and damper British climate compared to that of their native range in the south-eastern United States. Most of the terrapins in Britain’s waterways most likely found themselves there a long time ago when they were still young. These voracious predators grow extremely quickly and they soon grew too large for their owners to handle and so were unfortunately dumped (as already discussed). With no natural predators the terrapins did what they could to survive devouring newts, fish and possibly the young of birds. It’s not known how much of an impact they’re having on freshwater ecosystems nationwide but it is definitely an area of future research. Unfortunately the terrapins that are clinging on are usually quite ill as they aren’t getting the right vitamins and minerals needed as well as the correct amount of UV light. Britain used to be home to the European pond terrapin (Emys orbicularis) but unfortunately we lost our native populations of these due to climatic cooling.

A midwife toad from the population I currently monitor in Cambridge

A midwife toad from the population I currently monitor in Cambridge

One unusual non-native species that I’ve been working closely with for some time now is the common midwife toad (Alytes obstetricans). The first population of this species was established in Bedford in 1903 and since it has been a seed for further populations around the UK however we’re not sure if this is the case for the population in Cambridge. As with the other populations we know that the Cambridge one is breeding and with some colleagues I’m currently trying to establish whether or not the toads are infected with the amphibian chytrid fungus (Batrachochytrium dendrobatidis). We’re hoping to have screened the whole population by the end of next summer, the toads are notoriously hard to find and so we’re using photography as well as biometrics in order to identify individuals. Expect some updates on this topic in the near future as we plan to start collecting swabs again in April as long as the weather permits.

A corn snake which I collected from a Cambridgeshire resident's garden

A corn snake which I collected from a Cambridgeshire resident’s garden

The final example I’m going to leave you with is the corn snake (Pantherophis guttatus). These are an extremely popular pet and when young are extremely good escape artists. Back in the summer of 2014 I received a phone call from a concerned gentleman whom had found an orange snake in his compost heap. He’d taken some photos and sent them to FrogLife who’d confirmed it was indeed a corn snake. They weren’t willing to collect it and remove and so they passed on my details. When myself and a colleague arrived at the property we were expecting a fully grown adult so we’d come prepared with hooks and buckets. It wasn’t until we located the snake that we realised how small it really was. The snake can’t have been any older than a few months and resembled a shoelace in dimensions. After capturing and securing her in a temporary housing we took her to a local vet for a health checkup. She passed with flying colours and after an attempt to locate her owner, we decided to keep her and she has since been used in a number of outreach events and even participated in lectures I’ve given to undergraduates.

Of the 21 non-native reptile and amphibian species I mentioned at the beginning of this post, I’ve talked about 3 in detail – the three in which I have the most experience with. Not all of the non-native species will negatively affect our native species and ecosystems but as the climate warms the likelihood of more species becoming established is an ever danger threat. In order to protect our native herpetofauna we need to assess each non-native species in their current state and try to model what would happen if the climate warmed. In my eyes non-native species don’t always have to be extinguished or eradicated, we’ve welcomed the grey squirrel (Sciurus carolinensis) and Munjac deer (Muntiacus reevesi). Is it only a matter of time until we accept some of our newly acquired reptile and amphibian species?

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Steve Allain

Steve Allain

Chairman at Cambridgeshire and Peterborough Amphibian and Reptile Group
Steve is a current Master's student at Imperial College London and zoology graduate from Anglia Ruskin University. He has a particular passion and focus on British amphibian and reptile species. He is the current chairman of the Cambridgeshire and Peterborough Amphibian & Reptile Group (CPARG) and helps to organise and coordinate a number of amphibian and reptile surveys around the county, to map the distribution of herpetofauna within Cambridgeshire. Recently he has become interested in the amphibians of the tropics, especially South-East Asia after a trip to Borneo in 2015. Steve was an intern with the IUCN’s SSC Amphibian Red Listing Authority where he specialised in the red listing of South-East Asia’s amphibians. Steve is also a member of the SAVE THE FROGS! Task Force and a former blogger for The Wandering Herpetologist.
Steve Allain

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2 Responses

  1. Avatar John Burton says:

    An interesting piece; thanks for alerting me

  2. Great article, however I wonder if ecosystems are a little more finely balanced. Grey squirrels are not welcomed everywhere. They eat hazel nuts before they are ripe and will take all of them,burying or leaving none for dormice which are struggling anyway. Hazel hardly ever spreads by seed nowadays and is a much reduced species.

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