SOCIAL-INTERACTION ALTERS ATTRACTION TO COMPETITORS ODOR IN THE MOOSEMUS-SPRETUS LATASTE

When animals defend territories that are large and structurally comple x, scent marks alone are unlikely to be reliable signals of a resident 's dominance and competitors should require initial proof through dire ct interaction. This was tested using freshly captured Mus spretus whi ch occupy large non-overlapping ranges in grassland but are strongly a ttracted to substrate odours from unfamiliar competitors. Choice tests measured time spent investigating and chewing to gain access to paire d nestboxes when the entrances were blocked with mesh. Experiment I es tablished that mice of both sexes were more strongly attracted to thei r 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) are na. 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, subordin ates avoided their dominant competitor's odour in favour of their own while dominants continued to be attracted to both. There was little ag gressive competition between unfamiliar females and relative status di d 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 t o interaction but showed less attraction to a. competitor's odour post -interaction. A third experiment showed that the odour of an unfamilia r male was more attractive than that from an unfamiliar female, especi ally to males. The consequences of these responses for maintaining spa tial dispersion in this species are discussed. (C) 1997 The Associatio n for the Study of Animal Behaviour.