The response of subordinate male mice to scent marks varies in relation to their own competitive ability

Previous work has shown that dominant male mice, Mus musculus, are usually attracted to scent-marked areas while subordinates avoid them. In this study, the responses of subordinates were highly variable, and the idea that the probability of intruding onto a scent-marked substrate depends on their competitive ability was tested. Subjects were kept in dominant/subordinate pairs of males and tested with scent marks of an unfamiliar male. Subordinates who were large in relation to their dominant partners were more likely to choose a scent-marked substrate in a Y-maze choice against a blank substrate; relatively small subordinates were more likely to avoid scent marks. Males that chose scent marks also tended (P=0.08) to be more often involved in escalated contests with their dominant partners. Body size is known to affect the outcome of fights between strangers and these results could be explained if relatively large subordinates are (1) more likely to be able to defeat the resident of a scent-marked area (and thus benefit from its resources) and (2) if large subordinates pose a greater threat of a dominance reversal to their dominant partners than would a relatively small subordinate. (C) 1996 The Association for the study of Animal Behaviour