In two closely related species, females generally prefer conspecific males over heterospecific males. We found that estrous (but not diestrous) female Syrian hamsters Mesocricetus auratus prefer the odors of conspecific males to odors of Turkish hamsters Mesocricetus brandti. However, female Syrian hamsters are not aggressive toward male Turkish hamsters and will readily mate with them. We hypothesize that many generations in captivity led to a reduction in females' ability to avoid inter-species mating, possibly related to the heightened sexual receptivity observed in Mesocricetus hamsters in captivity. To test this hypothesis, we replicated a study carried out with female Turkish hamsters soon after the current laboratory stock of this species was established. In that study, female Turkish hamsters showed lordosis toward male Syrian hamsters in only 20% of interactions and attacked heterospecific males in 80% of the pairings. Using animals descended from that original colony (after many generations in captivity and certain episodes of inbreeding), 100% of female Turkish hamsters mated with heterospecific males and none showed aggression toward heterospecific males. Thus female avoidance of interspecific mating may be affected by captive rearing conditions.

Golden hamsters (Mesocricetus auratus) use olfactory cues to assess traits of conspecifics such as kinship, individual identity, and reproductive status. The environment, however, is full of a wide variety of other olfactory information such as signals emitted by some of the hamster’s primary predators. Given this, we hypothesized that hamsters use odors from predators as an indirect sign of increased predation risk in the environment. In addition, based on data that show that wild hamsters are diurnal while laboratory hamsters are nocturnal, we hypothesized that if golden hamsters did respond to the predator odors, perceived predator risk might influence daily activity patterns in hamsters. We tested male and female hamsters over 5 d with scent gland secretion from domestic ferrets (Mustela putorius furo) and compared their behavior to that observed when they were exposed to a clean arena. In response to the predator odor, subjects significantly decreased the amount of time active outside of their burrow, returned to their burrow more quickly, and spent less time near the predator odor than the clean control stimulus. These results strongly support our hypothesis that hamsters, like other species of small mammals, avoid predator odors. The results did not, however, support our second hypothesis that exposure to predator odors during the dark phase of the light cycle would elicit a switch to a more diurnal pattern of activity. More work is needed to understand how environmental cues and internal mechanisms interact to shape activity patterns.