You dirty rat! Or are you?

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The one thing we all know about rats is that when you're in London you're never more than a certain distance from one, a distance which, depending on who you ask, varies from 20 yards to 10 feet. Of course this is no more than an unpleasant way of expressing statistics about the rat population and the human population over a given area, but the idea that each of us is being stalked by our own personal rat is certainly compelling, not to mention disturbing.

Rats have long inspired irrational fear as a disease-ridden, unstoppable menace, capable of chewing through concrete, killing cats, ingesting poison with no ill-effects, side-stepping traps, breeding exponentially, doling out plague and generally taking over. We imagine one day they will outnumber us (actually they already do).

Now a new book from Australia, The Story of Rats (Allen & Unwin), aims to set the record straight. Written by S Anthony Barnett, a professor of biology who was introduced to rats while working on the London Underground during the Blitz, it dispels a few rat myths.

The naming of rats is itself a primary source of confusion. The two main species are the black rat (Rattus rattus) and the brown rat (Rattus norvegicus), either of which can be black or brown. Rattus norvegicus is sometimes called the Norway rat, although it doesn't actually come from Norway. The black rat was once Britain's king rat, unchallenged for more than 2,000 years, and was responsible for spreading bubonic plague through infected fleas. The Norway invaded (from Russia, probably) in the 18th century and, for reasons which are still unclear, began to take over. Until the early 20th century, black rats were called roof rats because they were found in attics, while their rival Norways kept mostly to sewers. Today, the black rat is all but extinct in Britain, confined to small colonies on Lundy and the Hebrides. From time to time newspapers print scare stories about the 'plague' rat returning to our shores, but Norways can spread disease as well as the next rat.

And plague is the least of our problems. Rats also carry Weil's disease, roundworm, amoebic dysentery, salmonella and a variety of viruses. Contact with them or their droppings can cause toxoplasmosis or pneumonia. Since the Second World War, our rat problem has been getting steadily bigger. The British rat population has now reached 70 million; there are more rats in Britain than there are Britons. Local authority cutbacks and global warming have been blamed for recent surges in numbers, which jumped by 50 per cent in the Home Counties last year. Perhaps, by the time you finish reading this article, your personal rat stalker will have moved a few feet closer.

One of the creepiest things about rats is their lack of fussiness; they'll eat absolutely anything. While they are naturally adapted for a diet of grain, hungry rats will eat snails, fish, vegetables, raw meat, animal feed, carrion and soap, as well as all manner of processed food. Oddly, however, their varied diet makes them difficult to poison. Rats are cautious; they sample strange foods in small quantities, and learn to avoid common toxins through aversion. Anticoagulants like warfarin, which kill rats by inducing internal bleeding, get round this, but a certain percentage of rats are genetically immune to their effects. As a consequence a poison-resistant population is now on the rise.

While they appear to be clever, even cunning, describing rats as intelligent is misleading. Some people claim they have higher IQs than dogs, but what does this mean? Can a rat catch a Frisbee? By some measures of intelligence, rats outperform dogs, but then so do octopuses. What is clear is that rats are highly adapted to living alongside humans, and a natural curiosity drives them to seek out new habitats and food sources, while a fear of unfamiliar objects protects them from our efforts to exterminate them. Through exploration, they find new solutions to problems. In their own ratty way, rats think.

We may find rats difficult to control, but one particular breed of rat has inadvertently been controlling our behaviour for over a century: the white domesticated Norway, or the lab rat. Much of our understanding of human intelligence, learning and conditioning was discovered by putting lab rats through their paces in mazes. Rightly or wrongly, many of the ways in which we educate, medicate and control humans are based on theories developed by scientists observing rats.

Perhaps the reason we hate rats so much is because they remind us of ourselves. Like us, they're omnivorous, opportunist and social. They live where we live, they eat what we eat and they adapt to any adjustments in our environment as readily as if we had changed things for their express comfort and enjoyment. If we can take one consolation from their astounding success, it's that we made them what they are today. They'd be nothing without us, and when we're gone, they'll have to go, too.

 

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