Oestrus and the vaginal smear cycle of the river otter, Lutra canadensis

Abstract

Vaginal smears of river otters contained specific cellular associations which can be used to monitor their reproductive cycle. The anoestrous period was identified by the presence of large intermediate epithelial cells while the onset of pro-oestrus was gradual and the duration difficult to determine. Oestrus was indicated by an influx of nucleated and non-nucleated cornified cells which continue after mating. The metoestrous smear was characterized by large quantities of leucocytes and mucus.