From Hans Zinsser’s scholarly and delightful book Rats, Lice, and History: Being a Study in Biography, Which, After Twelve Preliminary Chapters Indispensable for the Preparation of the Lay Reader, Deals With the Life History of Typhus Fever comes the following:
More than any other species of animal, the rat and mouse have become dependent on man, and in doing so they have developed characteristics which are amazingly human. In the first place, like man, the rat has become practically omnivorous. It eats anything that lets it and – like man – devours its own kind, under stress. It breeds in all seasons and – again like man – it is most amorous in the springtime. It hybridizes easily, and, judging by the strained relationship between the black and the brown rat, develops social or racial prejudices against this practice. The sex proportions are like those among us. Inbreeding takes place readily. The males are larger, the females fatter. It adapts itself to all types of climates. It makes ferocious war upon its own kind, but has not, as yet, become nationalized. So far it has still stuck to tribal wars – like man before nations were invented. If it continues to ape man as heretofore we may, in a few centuries, have French rats eating German ones, or Nazi rats attacking Communist or Jewish rats; however, such a degree of civilization is probably not within the capabilities of any mere animal.
The book is lighthearted, erudite, and without question the best book about vermin and pestilence you have ever read.