Abstract
The role of physical contact in the induction of irregularities in the estrous cycle of grouped mice and the hormonal control of the production of the operative stimulus were investigated. Thirty females unisexually housed in a cage in contact with each other exhibited prolongation of the estrous cycle; by contrast, 30 females individually housed in the compartments of a partitioned cage exhibited normal estrous cycles. Increasing the cage density to 50 females resulted in a further increase in the incidence of prolonged cycles. An intact female housed in free contact with ovariectomized or orchidectomized conspecifics exhibited a high percentage of prolonged cycles whereas an intact female prevented from having physical contact with gonadectomized conspecifics exhibited normal estrous cycles. The results emphasize that physical contact between individuals plays a major role in the induction of estrous cycle irregularities in unisexually grouped females and that ovarian hormones are not involved in the production of the estrous cycle-disrupting stimulus.
