Seasonal Changes in the Hormonal Response of Male Eversmann’s Hamsters (Allocricetulus eversmanni, Cricetinae, Rodentia) to Olfactory Signals from Conspecific Females

Abstract

Reproductive success demands both the male and female reaching a particular physiological status, which is usually stimulated in rodents by certain olfactory signals. The hormonal response of male Eversmann’s hamster (Allocricetulus eversmanni) to the natural excretions (urine, midventral gland secretion (MVGS) of conspecific females was studied during several seasons of the year, with the animals kept in conditions of natural lighting and temperature. In the fall, no reliable changes in the testosterone level in males in response to any signal presented were noted. In the winter and spring, a reliable (P< 0.05) increase in the testosterone level was caused by the female MVGS odor. In the summer, a similar reaction only to conspecific female urine (P< 0.05) was noted. Moreover, in the summer and fall, males showed a reliable decrease in the cortisol level in response to the odor of female urine (P< 0.05). In the winter and spring, a similar result was caused by exposure to both odors. The progesterone level in males reliably (P< 0.05) increased upon exposure to both female urine and MVGS in all seasons of the year, except for the female MVGS in the summer. Therefore, the decreased cortisol level in combination with the simultaneously increased testosterone and progesterone levels allow the males of the species under study to achieve their maximum reproductive success, despite the high degree of their intraspecific aggression.