Preference of Syrian hamsters to nest in old versus new bedding

This study tested whether Syrian hamsters (Mesocricetus auratus) have an aversion to old bedding (up to 14 days) by offering them the option to nest in a new cage. A secondary goal was to assess the relative value of shelters by testing whether the tendency to nest in the new cage was reduced when a shelter was present in the old cage. Individual hamsters were placed in two cages connected by a tunnel, and left to familiarize themselves with this set-up for 10 days. Then the bedding was changed in each cage, and for the next 3, 9, or 14 days the tunnel was blocked and each hamster lived in only one of the cages, either with or without a shelter (PVC pipe) present in that cage. Then the tunnel was unblocked and for the next 3 days the position of each hamster's nest in either of the two cages was noted. After 3, 9, and 14 days in the old cage, respectively 10, 11, and 8 out of 15 males and 6, 9, and 3 out of 15 females never nested in the new cage, whether the old cage had a shelter or not. Only 2, 1, and 4 out of 15 males, and only 5, 3, and 5 out of 15 females nested in the new cage more than in the old one in the absence of shelters. Of those males that nested in the new cage at least once, three out of five, three out of four, and five out of seven nested in the new cage less often when a shelter was present in the old cage than when no shelter was present. For females, the corresponding numbers were 8 out of 9, 5 out of 6, and 11 out of 12. These results indicate that access to a new (though still familiar) cage with fresh bedding holds only a small attraction for nesting hamsters, at least when their current bedding is up to 14 days old, and that shelters are valued.