Male-induced estrus synchronization in the female Siberian hamster (Phodopus sungorus sungorus).

Olfactory cues play an integral role in the organization of events that mediate reproductive success. In a variety of species, priming pheromones, in particular, are important for ensuring reproductive fitness. To date, very little research has focused on how male-emitted priming pheromones, such as those that regulate the onset of puberty and estrus synchronization in females, affect the reproductive physiology of the female Siberian hamster (Phodopus sungorus sungorus). This lack of research may be due to the physiology of the Phodopus genus; vaginal cytology cannot be used as a reliable indicator of estrus or ovulation. Using a jugular cannulation technique to determine estrous stage by blood analysis of prolactin and luteinizing hormone, we sought to determine if male priming pheromones affect estrous cyclicity in the female Siberian hamster and, if so, whether the production of these priming pheromones is androgen dependent. Our results showed that females exposed to bedding from mature, intact males showed a significantly higher incidence of proestrus 3 days later than did females exposed to the bedding of mature, gonadectomized males. Therefore, we found that not only do male Siberian hamsters emit chemical signals that induce estrus synchronization, but also that this ability is likely to be androgen dependent.