Seasonal changes in the testis and epididymis of the American Grey squirrel, Sciurus carolinensis

The histological changes in the testis and epididymis of the American Grey squirrel, Sciurus carolinensis (Gmelin) during development and the testicular cycle are described. It was observed that male Grey squirrels, as a population, did not undergo a pronounced seasonal reproductive cycle, however, individual males did experience periods of reproductive inactivity which were asynchronous and not related to seasonal changes in the environment. It is suggested that the individual sexual cycles are due to an endogenous rhythm of gonadotrophin secretion by the pituitaries of these animals.