Are we really only never more than six feet away from a rat? Having spent most of my working life in the City of London I can well believe it but if we are talking about rattus norvegicus I have never been convinced. I can count the number of times I have seen a real live rat on my fingers and toes and, perhaps, have one or two left over. What I do know is that they are no respecter of surroundings. I have seen one in a so-called luxury hotel, scuttling across the bar area to the consternation of some and the amusement of the other guests, and others, as you might expect, rummaging around rubbish piles. Normally, they are shy creatures and go out of their way to avoid humans.
It is difficult to know how this canard has come about. One finger of suspicion has been pointed at WR Boetler who in his 1909 blockbuster, The Rat Problem, tried to establish whether it was reasonable to suppose that there was one rat for every acre of cultivated land in the UK. He was reduced to making an educated guess but as there were 40 million acres of farm land at the time and a UK population of 40 million the conclusion that there was one rate for every one of us was too tempting to resist.
Let’s look at the problem another way. If we assume that a rat has a circular area to itself then in order for it to never be more than six feet away from where we may happen to be, the circular area it will occupy will be some 11.49 square metres. The UK occupies some 245 billion square metres and so for rats to be evenly distributed in their 11.49 square metre areas there would have to be some 21.3 billion of them. This seems highly unlikely.
Fortunately, Dr Dave Cowan of the Food and Environment Research Agency can provide us with some assistance. The first thing is to know something about rats and the particular nugget of wisdom that helps is that they are completely commensal here in Blighty. In other words, they have a symbiotic relationship with humans. There are four places where rats may be found – in and around our houses, in commercial premises, down sewers and on agricultural premises. We can now do the maths.
It is very rare for rats to live in our houses – around 0.5% are infested – but they are more common outside in gardens, compost heaps and outbuildings. Even so, only 3% of premises have a problem with rats and where they are, there are relatively few of them of them. Cowan calculated the number of domestic rats at around 1.5 million. 5% of the 1.8 million commercial premises have rats in residence, a measly total of around 200,000. There are around 16,000 square kilometres of sewers in the UK of which around 5% have rats. In the 1950s a survey was conducted into the number of rats in sewers and a figure of 2,000 per square kilometre was arrived at. This means that there are some 1.6 down the sewers, making a total of around 3 to 3.5 million in urban environments.
If we move to the country, the picture is somewhat different. Around 40% of the 200,000 agricultural premises in the UK have rats and on average there are 90 rats on a farm. Multiplying it all up gives us some 7 million rural rats and some 10.5 million rats overall.
The UK has around 16,000 square kilometres of urban space and so if all the urban rats were distributed evenly they would have 5,000 square metres to roam around each. If you were standing in any one spot in an urban environment at worst you would be some 50 metres away from a rat.
Makes me feel so much better!