Hibernation in the female Turkish hamster (Mesocricetus brandti): an investigation of the role of the ovaries and of photoperiod.

The possible role of the ovaries in hibernation was examined by comparing patterns of hibernation in intact and ovariectomized Turkish hamsters (Mesocricetus brandti). Ovariectomy had little, if any, effect on hibernation in these studies. However, females which were anovulatory prior to cold exposure entered hibernation more rapidly as compared to cycling females. Most females (both intact and ovariectomized) maintained in short days returned to a second phase of hibernation several months after terminating the initial phase. In contrast, most females housed in long days failed to show a second phase of hibernation. Thus, it is possible that effects of day length may be more important than effects of ovarian hormones in regulating hibernation in the female Turkish hamster.