“This great law,” Mr. F. proceeds, “pervades and affects the whole animal creation, and so active, unwearied, and rapid is the principle of increase over the means of subsistence amongst the inferior animals, that it is evident whole genera of carnivorous beings amongst beasts, birds, fish, reptiles, and insects, have been created for the express purpose (?) of suppressing the redundancy of others, and restraining their numbers within proper limits.
“But even the natural checks are insufficient to restrain the effects of a too-rapid populative principle in some animals, which have, therefore, certain destructive propensities given to them by the Creator, that operate powerfully upon themselves and their offspring, as may be particularly observed in the natural history of the rabbit, but which is still more evidently and strikingly displayed in the life and economy of the rat.
“It has been calculated by Mr. Pennant, and there can be no doubt of the truth of the statement, that the astonishing number of 1,274,840 may be produced from a single pair of rabbits in the short space of four years, as these animals in their wild state breed seven times in a-year, and generally produce eight young ones each time. They are capable of procreation at the age of five or six months, and the doe carries her burthen no more than thirty days.
“But the principle of increase is much more powerful, active, and effective in the common grey rat than in any other animal of equal size. This destructive animal is continually under the furor of animal love. The female carries her young for one month only; and she seldom or never produces a less number than twelve, but sometimes as many as eighteen at a litter—the medium number may be taken for an average—and the period of gestation, though of such short continuance, is confined to no particular season of the year.
“The embraces of the male are admitted immediately after the birth of the vindictive progeny; and it is a fact which I have ascertained beyond any doubt, that the female suckles her young ones almost to the very moment when another litter is dropping into the world as their successors.
“A celebrated Yorkshire rat-catcher whom I have occasionally employed, one day killed a large female rat, that was in the act of suckling twelve young ones, which had attained a very considerable growth; nevertheless, upon opening her swollen body, he found thirteen quick young, that were within a few days of their birth. Supposing, therefore, that the rat produces ten litters in the course of a year, and that no check on their increase should operate destructively for the space of four years, a number not far short of 3,000,000 might be produced from a single pair in that time!
“Now, the consequence of such an active and productive principle of increase, if suffered continually to operate without check, would soon be fatally obvious. We have heard of fertile plains devastated, and large towns undermined, in Spain, by rabbits; and even that a military force from Rome was once requested of the great Augustus to suppress the astonishing numbers of the same animal overrunning the island of Majorca and Minorca. This circumstance is recorded by Pliny.
“If, therefore, rats were suffered to multiply without the restraint of the most powerful and positive natural checks, not only would fertile plains and rich cities be undermined and destroyed, but the whole surface of the earth in a very few years would be rendered a barren and hideous waste, covered with myriads of famished grey rats, against which man himself would contend in vain. But the same Almighty Being who perceived a necessity for their existence, has also restricted their numbers within proper bounds, by creating to them many very powerful enemies, and still more effectually by establishing a propensity in themselves, the gratification of which has continually the effect of lessening their numbers, even more than any of their foreign enemies.
“The male rat has an insatiable thirst for the blood of his own offspring; the female, being aware of this passion, hides her young in such secret places as she supposes likely to escape notice or discovery, till her progeny are old enough to venture forth and stand upon their own energies; but, notwithstanding this precaution, the male rat frequently discovers them, and destroys as many as he can; nor is the defence of the mother any very effectual protection, since she herself sometimes falls a victim to her temerity and her maternal tenderness.
“Besides this propensity to the destruction of their own offspring, when other food fails them, rats hunt down and prey upon each other with the most ferocious and desperate avidity, inasmuch as it not unfrequently happens, in a colony of these destructive animals, that a single male of more than ordinary powers, after having overcome and devoured all competitors with the exception of a few females, reigns the sole bloody and much-dreaded tyrant over a considerable territory, dwelling by himself in some solitary hole, and never appearing abroad without spreading terror and dismay even amongst the females whose embraces he seeks. In this relentless and bloody character may be found one of the most powerful and positive of the checks which operate to the repression of this species within proper bounds; a character which attaches, in a greater or less degree, to the whole Mus genus, and in which we may readily perceive the cause of the extirpation of the old black rats of England, Mus rathus; for the large grey rats, having superior bodily powers united to the same carnivorous propensities, would easily conquer and destroy their black opponents wherever they could be found, and whenever they met to dispute the title of possession or of sovereignty.”