We had concerns that the unusually hot summer would provide the terrapins, which originate from north American swamps, with the right weather to start multiplying. As a non-indigenous species, an explosion in numbers could potentially lead to the decline of native wildlife including frogs, fish and even ducklings.
A huge craze of keeping terrapins as pets followed the popularity of the Teenage Mutant Ninja Turtles cartoon in the late-1980s and early-90s. However, many were illegally dumped into the wild once they had grown too big for domestic fish tanks in family homes – leading to an European wide ban on the species.
While not uncommon to see larger ‘dinner plate-sized' terrapins from that period now swimming or basking in the sunshine on local waterways, numbers have remained constant due to the need for sustained periods of hot weather before they can breed – something this year's scorching summer may have provided.
Bad news for conservation
Paul Wilkinson, ecologist at the Canal & River Trust, said: “From a scientific point of view this is very interesting, but could be bad news for conservation. We've been concerned that the trend of increasing temperatures associated with climate change would give terrapins the conditions they need to successfully breed, something which could be a disaster for some native wildlife.
"We've heard anecdotal reports that eggs had been laid. Now we've found this juvenile, the hunt is on to see if there are more out there, especially if they are displaying their egg teeth – a sign that they are recent hatchlings.
“Terrapins are native to the eastern states of North America, such as Florida. They need extremely warm, sustained weather, something we obviously experienced over the past few months. It's particularly noticeable in towns and cities which can become ‘heat islands' in the summer – which could explain this finding on the canal in London.
“We'd be keen to hear from anyone who has spotted a match-box sized terrapin. It would help us to determine that they are definitely breeding, and by finding out where this is taking place it will enable us to see the extent of the problem and what measures we might be able to take.”
The terrapin was found in Lisson Grove, near Marylebone, on the Regent's Canal. At 27-degrees celsius it takes terrapins around 120 days to hatch, incubation is faster in hotter temperatures normally requiring a warm spring to get the females ready for mating.
It is illegal to release terrapins, which can live up to 40 years, into the wild.