Man's Enemy—The Rat
AT some future time a world-wide effort will be made to exterminate the rat. He is a filthy beast, responsible for much disease amongst men. His chief speciality in this line,. the Black Death or bubonic plague, is no longer a serious problem in Europe ; but he was practically the sole agent of infection (by means of the rat-flea) during the Middle Ages. At present the diseases which he is known to convey are malig- nant jaundice, parasitic mange, tapeworm, and rat-bite fever He is under suspicion for outbreaks of distemper and foot- and-mouth disease amongst domestic animals. Rats also suffer from cancer, and figures seem to suggest a correlation. between the degree in which a district is rat-infested and the number of human deaths from cancer in the district. Here, however, nothing definite has been proved against the rat.
The rat population of England is estimated at fifty millions —a little larger than the human population. Every rat costs about £2 a year for his upkeep—in food eaten and food spoiled, commercial stocks destroyed and buildings damaged. Our total material loss from rats is, therefore, some hundred million pounds a year. Nobody likes rats ; or, at least, nobody in his senses likes them. They can be directly dangerous to human life. An instance is quoted by Mr. Moore Hogarth in his very thorough and valuable monograph : " In the Walker Colliery, near Killingworth, in which many horses were employed, the rats had accumulated in great multitudes. It was customary at holiday times to bring to the surface the horses and the fodder, and to close the pit for a time. On one occasion, when the holiday had extended to ten days or a fortnight . . . the first man who descended was attacked by the starving rats and speedily killed and devoured."
The only good word that can be said for rats is that they are scavengers and clear off a certain amount of refuse : but in a decently clean civilization, there should be no need for their aid ; and, in any case, it is precisely their commerce with garbage which makes them dangerous to health.
The difficulties in the way of defeating this enemy of mankind are admirably described by Mr. Hogarth. The problem of the rat, he remarks, is an international problem. Unless the whole world combines, no country can do more than kill oft the rats within its own borders and strive continually to repel invaders. In this respect Great Britain is very for- tunately placed, and the vigilance of the authorities at our ports has produced a great improvement. Even in Great Britain, however, it is impossible to prevent all invasion ; and the fecundity of rats is so great that (in theory) a single pair within four years can have more than ten million des- cendants. The same consideration holds between one district and another, and between one property owner and another. Where a local authority is slack, the neighbouring authorities are soon overrun. It is a desperate job for one man to keep down the rats on his premises, if the man next door is providing " nurseries or hostels " in which they can multiply.
Our world-wide effort, therefore, would demand an organ- ization of which we are at present incapable. The problem will have to be dealt with both on the widest scale; between one nation and another, and on the smallest,-by the co-opera- tion of individuals. As the Americans would put it, we must become " rat-conscious." An interesting example of the closeness of organization that would be required is shown in the plan for exterminating rats which in these circumstances would promise the greatest success. Under the Rodier System the rats are trapped, the females killed, and the males liberated. If, by this means, the males came to out- number the females considerably, the problem would solve itself : the male rats would so persecute the females that it would be impossible for them to breed, and any young ones that might be born would be killed. Wherever this plan has been carried out in some sufficiently isolated locality, it has proved extraordinarily successful. The chief obstacle to its adoption Hex in the fact that it is not easy to carry out unless no other method of extermination is being tried : the crucial point of the system is that only females should be killed. Readers who might suspect the efficiency of this system should remember that when we wish to multiply animals (as in domestic breeding), we take precisely the opposite course—preserve the females and reduce the proportion of males.
Meanwhile, there is no single method which can be advocated as best. Traps, poisons, bacterial cultures, flooding and smoking, are all necessary, and Mr. Hogarth gives precise directions for their employment. We have a Rats Act in England, and a yearly Rat Week ; but these measures have proved insufficient, even to keep up a satisfactory guerilla warfare.- As Mr. Hogarth dramaticallY says, " the rats practically laugh us to scorn." One of the deficiencies in the Rats Act is that the onus of destruction is thrown on the occupier ; and some of the worst infested premises are the hovels of poor people who can hardly afford the necessities of life and have certainly no money to spare for traps or poisons.
So far we have sounded rather dismal about the prospects of defeating this common enemy ; but it should not be thought that efforts can be relaxed or that we can wait till the world is perfectly organized. It is certainly possible by vigilance and constant activity to keep down the number of rats and minimise the damage they do. It would be disastrous to slacken our efforts ; and any increase in activity brings its own reward. We must put off into the future that golden age when we shall be able to forget the whole problem because it has already been solved ; and at present we must take every means of suppressing a danger of which we cannot entirely rid ourselves. .
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