KILLER TURTLES IN THE THAMES
Ian Thomson fears an
invasion of carnivores in home waters
TURTLES have recently made quite a splash in the news. Some have put in the odd television appearance. These are not the run-of-the-mill turtles that end up as soup in your tureen, but rather the fero- cious snapper and alligator varieties, sever- al of which are rumoured to have found their way into the Thames.
Weighing up to 40 and 200 lb respective- ly when adult, both snapper and alligator are liable to lunge at more or less anything that moves. In North America, bathers have been known to lose toes, fingers and even arms to the carnivores. These `killer turtles' are a disturbing symptom of what Thames Water and the RSPCA now con- sider cause for serious concern: the dump- ing of fish or other wildlife — terrapins, rogue pike, tropical angel fish — into Britain's ponds, rivers and lakes. These create enough problems, but should there be carnivorous turtles in the Thames, `the effect', according to Brig Daniels, a Thames Water spokeswoman, `would be catastrophic'.
Catastrophic? Surely not. But Mrs Daniels is serious: 'Both snapper and alligator have the reputation — excuse my French — of being utter bastards. Nasty, voracious, aggressive, there is really very little to recommend them. Fish and mol- luscs are their preferred food, but if it's water-fowl they're after — ducklings, let's say — then these turtles will drag the bird below water to drown before devouring it. One of the most horrifying things I've seen was a pike getting hold of a swan's leg. A bad-tempered carnivorous turtle will do the same and it won't think twice about taking a chunk out of a human either. Should it turn out that these turtles have indeed been dumped into the Thames', she continued, 'I certainly won't be dipping my toes into the river.'
When fully grown, the common snapper measures about four feet from snout to tip of tail, and has a head the size of a small dog's. As ferocious as the wildest beast of prey, it can bite off a piece of plank more than an inch thick. You may fish for the brutes with bait, and had Izaak Walton published The Compleat Angler in 1987 instead of 1653, he might well have substi- tuted snapping turtles for pike `as the tyrant of the fresh water, because their life is maintained by the death of so many fish; which has made him by some writers to be called the fresh water wolf, by reason of his bold, greedy, devouring disposition'.
More seriously, Thames Water fishery officials believe the common snapper may play havoc with the finely-balanced 'eco- system' of the region's rivers and lakes. `Destroying stocks of small mammals, birds and fish, the turtles would become a top predator, and the only animal capable of preying on them would be man,' says Brig Daniels.
But would the snapper be suited to our cold climate? I asked Dr Christopher Andrews, Assistant Curator of the London Zoo aquarium: `No problem', he said. 'The range of both snapper and alligator extends from the Canadian lakes east of the Rocky Mountains, through the United States and Central America. So the beasts would easily be able to survive the rigours of our winter, breaking the ice with their power- ful snouts if need be.'
Dr Andrews also informed me that the common snapper has an unusual ability to sniff out dead and decaying animals; there is at least one case of North American Indians (who apparently get on very nicely with carnivorous turtles) 'using a snapper to locate dead bodies at the bottom of lakes for the police'. Who knows, maybe there's something in these turtles for the Metropolitan Police Force.
The Department of the Environment puts the number of snappers imported into Britain last year at 1,122, and 114 for alligators. But these figures apply only to people who actually have a licence, and Brig Daniels fears hundreds more 'may have come in through the back door', or via the pet trade. `There are many unpro- fessional pet shop owners who just don't know what they're selling,' she continued. `Baby snappers are sold at about the size of a 10 pence piece. They look very sweet and fit quite comfortably into a matchbox. Unsuspecting customers buy the turtles, only to release them into the Thames when they grow to an unmanageable size!'
Of course, turtles are not the only creatures to be thus abandoned. Mrs Daniels went on to say that a three-foot Pseudo-doras niger, or armour-plated South American catfish, was recently found suffering from `hypothermia' in the shallows of a tributary of the Thames in Isleworth, near a Watney's brewery. Need- less to say, it had been dumped. Dr Andrews spoke very highly of the hapless Pseudo-doras: 'A rare and magnificent beast. I would have gladly given the fish a home here at the Zoo had it not died of cold'.
It is no coincidence that the catfish was found near a brewery; the water there is warmer and doubtless more nutritious than anywhere else. The same goes for the water around sewage treatment plants and power stations, also favourite dumping grounds: 'Sometimes you'd think you were looking at an aquarium full of tropical fish,' says Brig Daniels, who has reported sightings of tropical oscars, south east Asian guerami, and angel fish.
Mrs Daniels added: `For the last five years, there has been a thriving colony of giant terrapins — each about the size of a small loaf of bread — in the Oxford canal. We also have a fair number of wild goldfish and seahorse in the Thames. On a more sinister note, a rare poisonous Mediterra- nean fish called a weaver was recently caught in the river at Gravesend.' More alarming still are the colonies of scorpions along the Central Line under- ground; originally brought over to Britain in crates of bananas, the creepy-crawlies are now living quite happily under the rails at Ongar. Underground ticket-collectors are apparently none too happy.
As far as the putative dumping of snap- ping turtles is concerned, Thames Water believe it is almost impossible to keep tabs on possible offenders. Under the 1981 Wildlife and Countryside Act, the fine for releasing a common snapper into the Thames is about £2,000. But Thames Water are sceptical as to its efficacy.
Dr Christopher Andrews, who inciden- tally keeps a `lonely hearts register for unwanted reptiles and tropical fish', was unable to show me a common snapper at the London Zoo aquarium. But he did have an ocean-going hawksbill, a distant cousin of both snapper and alligator now a protected species, as its shell is much sought after. I must say the hawksbill didn't look particularly ferocious, but then it was about half the size of the snapper, and didn't have much of a beak either. And unlike the snapper, the hawksbill had no fresh water algae growing on the mud caked around its shell — an ugly excresc- ence which renders its carnivorous cousin as inconspicuous as a rotten old log. I'd prefer a mock turtle.