The Influence of Exteroceptive Factors on the Estrous Cycle of the Collared Lemming (Dicrostonyx groenlandicus)

Abstract

The estrous cycle of the collared lemming (Dicrostonyx groenlandicus) was studied under laboratory conditions. Vaginal smears did not reveal a repetitive estrous cycle. Females with cornified vaginal smears were usually receptive whereas those with leucocyte smears were almost always nonreceptive. Postpartum estrus sometimes continued throughout the period of lactation. Ovaries (P < .001), uteri (P < .001) and adrenals (P < .05) were heavier in estrous than in diestrous females. Graafian follicles were both more numerous (P < .005) and larger (P < .001) in estrous than in diestrous females. There was no apparent difference in the influence on estrus of a fresh produce diet compared to a dry lab chow diet. On the basis of vaginal perforation and cornification, females maintained on 6 h photoperiod were less stimulated (P < .025) than those on 18 h photoperiod and females on 24 h photoperiod were more stimulated (P < .0005) than those on 18 h photoperiod. Vaginal perforation and estrus were induced by caging anestrous females with an intact male, with another female or adjacent to an intact male but not by caging them adjacent to another female or with a castrate male.