Housing Density and Aggression in Syrian Hamsters.

The Syrian hamster (Mesocricetus auratus) is a solitary and naturally territorial animal, with female hamsters being more aggressive than males. This behavior makes handling difficult because they are usually housed in groups, which can lead to aggressive behavior. The objective of this study was to refine the management of Syrian hamsters in order to minimize aggressiveness, reduce the animal injuries, and lessen the risk of accidents among laboratory animal technicians due to the hamster aggression during handling. The experiment was conducted at the Center for Animals Experimentation, Oswaldo Cruz Institute. Four groups of hamsters were observed by video recording: group 1 (group-housed males, 6 to 8 wk of age), group 2 (group-housed females 6 to 8 wk of age), group 3 (group-housed female, 3 to 4 wk of age), and group 4 (individually housed females, 6 to 8 wk of age). Group 1 animals were less aggressive and agitated both during housing and during handling by the animal technician as compared with groups 2 and 3. Groups 2 and 3 showed greater agitation and aggression. Marked reduction in the level of aggressiveness and agitation was observed in group 4 as compared with all other groups evaluated during handling by the animal technician. Male hamsters housed in groups of 4 and females housed individually have reduced risks of accident during handling, thereby averting distress and consequent physiologic alterations. Avoiding these risks is essential to obtaining reliable experimental results.