Social interaction alters attraction to competitor's odour in the mouse Mus spretus Lataste.

When animals defend territories that are large and structurally complex, scent marks alone are unlikely to be reliable signals of a resident's dominance and competitors should require initial proof through direct interaction. This was tested using freshly captured Mus spretus which occupy large non-overlapping ranges in grassland but are strongly attracted to substrate odours from unfamiliar competitors. Choice tests measured time spent investigating and chewing to gain access to paired nestboxes when the entrances were blocked with mesh. Experiment 1 established that mice of both sexes were more strongly attracted to their own odour than to a clean site. Experiment 2 examined choice between the subject's own odour and that of an unfamiliar same-sex competitor both before and after meeting the competitor in a neutral (clean) arena. Prior to interaction, males exerted much effort to gain access to both their own and their unfamiliar competitor's odour. Once relative dominance had been established through agonistic interaction, subordinates avoided their dominant competitor's odour in favour of their own while dominants continued to be attracted to both. There was little aggressive competition between unfamiliar females and relative status did not affect their attraction to a competitor's odour. Females tended to be more attracted to a competitor's odour than to their own prior to interaction but showed less attraction to a competitor's odour post-interaction. A third experiment showed that the odour of an unfamiliar male was more attractive than that from an unfamiliar female, especially to males. The consequences of these responses for maintaining spatial dispersion in this species are discussed.Copyright 1997 The Association for the Study of Animal Behaviour1997The Association for the Study of Animal Behaviour