It’s time for another Teenage Mutant Ninja Turtle film again, so I thought I’d get out ahead of the publicity juggernaut with an article about our very own Chelonian peril, the Red-Eared Terrapin, or Slider. They’re now a frequent sight on urban ponds in the UK and are often seen as something of a novelty, however they are actually currently listed as one of the 100 most invasive species in the world by the IUCN. They can live for 40 years, but there is scant information on their distribution and the severity of the issue on UK ponds, with some speculative reports suggesting a population of around 15,000 in London alone.
From the southern United States and Gulf of Mexico region, terrapins were a popular, cheap pet, and were often sold when around the size of a 50p piece. Care and feeding was relatively simple and their popularity as pets grew during the 80’s (damn ninja turtles!). Growth could be rapid and for many owners unexpected. Coupled with aggressive behaviour and the potential for transmission of salmonella, many families took the irresponsible option of letting them take their chances in municipal ponds and canals.
Fortunately, the presence of terrapins is largely restricted to ponds in urban or semi urban settings (as accessible dumping sites) where the environmental value and biodiversity may not be that high. This does not reduce the need to eradicate them, a process which should both be simple and cheap but which land owners seem reluctant to undertake. Perhaps this is because of their status as charismatic novelties with the visiting public?
Reaching the size of a large dinner plate, they are opportunistic and voracious omnivores and their presence in the ecosystems of small ponds can be devastating to invertebrate and small vertebrate populations and also reduce macrophyte cover, compounding the problem. There are also anecdotal reports of terrapins killing ducklings by dragging them underwater, but more serious danger to waterfowl perhaps lie in their tendency to use nests as basking areas, destroying or submerging them and potentially eating eggs. Exploiting an environmental niche in the UK, the Red-Eared Terrapin has no natural predator and due to its adaptable and varied diet, is able to grow largely unchecked. Other predators are out-competed while the loss of fish stocks may increase the homogenisation of flora already found in many over-polluted bodies of water. As ever, there has been the usual, responsible reaction to the issue of an invasive from certain media outlets (Terrapins that can bite the finger off a child’s finger are being dumped in the Lake district by owners who don’t realise how big they grow – a particular favourite of mine, mainly for the glorious sub-editing failure to trim down the title).
Removal of terrapins from our waterways should be a relatively straightforward process. They do not currently breed in the wild in the UK as they require a warm ambient temperature for over 60 consecutive days, though one incident of egg laying and nest building has been recorded in the south of England, and hatching does occur in areas of southern Europe. There has also been a recent report of a juvenile in London last year, but its provenance was unknown. Improving information on distribution and impact should be a primary concern and would not be overly difficult; interest groups such as anglers for example would be a useful source of knowledge.
Buying terrapins is illegal in this country as is their dumping (or that of any alien species) and the lack of breeding suggests that the issue should be self-resolving, as with a lifespan of 40 years, the majority of those purchased around the 80’s boom should die out in the next decade or so. However, the scary prospect does exist that as long hot summers increase in regularity, the chances for breeding in the UK improves for the Red-Eared Terrapin. For this reason alone, removal should be attempted wherever the need exists.
Perversely, American Mink may be one of the only species present in the country that is able to predate on terrapins, though this may also be possible for otter.
A Personal Nemesis!
I have myself made the odd attempt at catching Red-Eared Terrapins (I emphasise the word odd), working to remove 5 terrapins from a small nature reserve in Kings Cross, London. Attempting a number of traps that verged on the Heath Robinson-esque, I eventually sourced some outside assistance, contacting the Hampstead Heath Conservation Rangers
team, who had reported great success in removing terrapins from their bathing pools with a tried and tested trap. The rather ramshackle looking trap consisted of a 5ft by 5ft square of thick piping, plastic sheeting of about 1ft forming the walls of the trap and on which the Terrapins would not be able to gain a purchase. The bottom was lined with chicken wire. It was necessary for the trap to sit in relatively deep water and the combination of a basking area as well as some bait would prove an irresistible charm and they would slide into the enclosed area and become trapped. At least that was how it was supposed to work.
However the much-vaunted trap failed and the terrapins showed absolutely no interest in it, despite prodigious baiting with sprats. After 2 months of failure we finally threw in the towel. No sooner had we done this than a volunteer strolling along the side of the pond simply bent down and scooped a less-than-vigilant terrapin up one morning. This was soon followed by a second, scooped up in a net while out fixing vegetation rafts in a canoe.
Catching the Terrapins was one thing, deciding what to do with them then was another matter entirely. Trawling lists of contacts and in depth browsing of the internet only resulted in a number of recipes for Terrapin soup. They could not be re-released, (terrapins are a Schedule 9 species) but equally there was nowhere on site to home them and no contacts who were willing to take them. Eventually the pair was euthanized by a vet, but the issue caused such consternation amongst the volunteers that the three remaining terrapins were left much as they had been before.
Taking on the hard choices regarding animal culling is a key part of responsible site management, and to ignore or fudge the issue by pandering to elements within volunteering or staff risks endangering the future stability of the ecosystem and this should not be underestimated despite how small or urbanised the reserve.