The information in scent over-marks of golden hamsters

Abstract

Abstract. Although scent over-marking is a commonly observed behaviour among mammals, it has received little experimental attention. With regard to individual signatures, there are three types of information that might be obtained from such marks: (1) the scents might blend, thus creating a new odour quality but sacrificing individually distinctive information, (2) the scents might remain distinct, preserving individual identity information, or (3) the scent on top could mask the individual identity information in the bottom scent. These three possibilities were tested in golden hamsters for two scents (flank gland and vaginal secretions) that are deposited by hamsters using two distinct patterns of scent-marking behaviour. In an habituation paradigm, test animals were exposed on five successive trials to a simulated over-mark in which the scent from one individual was placed on top of scent from another individual. On the sixth (test) trial, males were exposed to two separate scents, one from a novel individual and the other from the individual that provided either the top or the bottom scent during the habituation trials. Results on the test trial were similar for both vaginal secretions (experiment 1) and flank gland scent (experiment 2). The novel scent was investigated more than the top scent, indicating that the top scent was familiar to the males, but the bottom scent and the novel scent were investigated equally, indicating that the bottom scent was not familiar. These results suggest that the distinctive information in the bottom scent was masked by that of the top scent; furthermore, they show that the other two possible phenomena (scents blending or remaining distinct) did not occur. This demonstration of scent masking may well be the first reported to date. The possible significance of over-marking in hamsters and other species is discussed, and it is suggested that the precision and thoroughness of covering one scent with another may relate to species differences in the information available in over-marks and therefore in the functions that such marks serve.