THE INFORMATION IN SCENT OVER-MARKS OF GOLDEN-HAMSTERS

Although scent over-marking is a commonly observed behaviour among mam mals, it has received little experimental attention. With regard to in dividual signatures, there are three types of information that might b e obtained from such marks: (1) the scents might blend, thus creating a new odour quality but sacrificing individually distinctive informati on, (2) the scents might remain distinct, preserving individual identi ty information, or (3) the scent on top could mask the individual iden tity information in the bottom scent. These three possibilities were t ested in golden hamsters for two scents (flank gland and vaginal secre tions) that are deposited by hamsters using two distinct patterns of s cent-marking behaviour. In an habituation paradigm, test animals were exposed on five successive trials to a simulated over-mark in which th e scent from one individual was placed on top of scent from another in dividual. On the sixth (test) trial, males were exposed to two separat e scents, one from a novel individual and the other from the individua l that provided either the top or the bottom scent during the habituat ion trials. Results on the test trial were similar for both vaginal se cretions (experiment 1) and flank gland scent (experiment 2). The nove l scent was investigated more than the top scent, indicating that the top scent was familiar to the males, but the bottom scent and the nove l scent were investigated equally, indicating that the bottom scent wa s 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 r emaining distinct) did not occur. This demonstration of scent masking may well be the first reported to date. The possible significance of o ver-marking in hamsters and other species is discussed, and it is sugg ested that the precision and thoroughness of covering one scent with a nother may relate to species differences in the information available in over-marks and therefore in the functions that such marks serve.