Rat Mating

Among complex land animals, an elaborate courtship is usual, but rats and other small animals are exceptions. Nevertheless, there is a large literature on the matting behavior of rats, surveyed by Beach, Bolles, Hinde and Larson. When references are not given below, they should be sought in these reviews.

If an adult male, recently deprived of female company, encounters a female be approaches and sniffs her, he may sniff and lick her genitalia, or he may omit this formality and try to mount her. If the female is not in entrus, she does not allow intro-mission: typically she kicks the male off, but she may merely walk away. If the female is in entrus she may herself take the initiative in approaching the male and nosing him. After the first contact she runs a short distance, and pauses; the male follows and mounts her; as the male presses on the female's flanks, she adopts a posture which permits intro-mission, with the coccygeal region raised and the tail to one side. The male performs pelvic thrusts and, if ejaculation does not occur, then leaps backwards. The whole contact takes only a few seconds. If ejaculation occurs, the male does not leap back, but pauses and then usually falls off to one side of the female.

In a typical encounter, about five initial intro-missions occur at short intervals without ejaculation; on the sixth, the female is inseminated, and there is then a refractory period of a few minutes is inseminated; and there is then is refractory period of a few minutes, after which the sequence is repeated, but with fewer preliminary intro-missions before ejaculation. The refractory period lengthen, but ejaculation occur progressively earlier one intro-missions have been resumed. There is consequently an apparent anomaly as the readiness to copulate declines, the readiness to ejaculate increases.

This behavior is characteristic of the whole species Rattus norvegicus; it has been observed in various laboratory strains and much of it also among wild rats. It differs substantially from the mating of some other rodents: the male guinea pig (Cavia) may rest for more than one hour after a single ejaculation. Whatever the species, the whole sequence is highly stereotyped; the typical behavior of each sex provides a clear example of a fixed action pattern.