Copulatory behavior of roof rats (Rattus rattus).

Abstract
The copulatory behavior of roof rats (R. rattus) was investigated. Females were brought into behavioral estrus with exogenous hormones [estradiol benzoate, progesterone], and each pair was observed until 30 min elapsed without copulation. Roof rats appeared to be similar to laboratory rats (R. norvegicus) with regard to basic motor patterns of copulation, quantitative measures of copulation, behaviors accompanying copulation, and postejaculatory ultrasonic vocalizations. Only patterns of tail rattling in females, climbing and allogrooming in both sexes, and an ability to ejaculate on a single insertion by males were observed in roof rats but not reported for laboratory rats. The role of various components of the copulatory pattern of male roof rats on the induction of pregnancy in normally cycling young females was assessed. A single ejaculation preceded by an abnormally high number of intromissions or 3 normal ejaculatory series maximized the incidence of pregnancy, whereas 1 normal ejaculatory series or 1 ejaculation preceded by an abnormally low number of intromissions did not.

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