THE ROLE OF SUBSTRATE ODORS IN MAINTAINING SOCIAL TOLERANCE BETWEEN MALE HOUSE MICE, MUS-MUSCULUS-DOMESTICUS - RELATEDNESS, INCIDENTAL KINSHIP EFFECTS AND THE ESTABLISHMENT OF SOCIAL-STATUS

Individually distinctive urinary odour cues deposited on the substrate are important in maintaining social relationships within and between social groups of house mice. The use of substrate odours depends on discriminable differences in odour between individuals and an ability to learn individual odours. Relatedness is one factor that is likely to reduce both of these properties through reducing differences in inherited odour cues between individuals. In keeping with this, familiar half-sibling male house mice showed a reduced tendency to discriminate against individuals that ceased to contribute urinary substrate odours compared with unrelated males. Furthermore, relatedness affected the development of aggression and substrate and social investigation within groups in ways consistent with increased difficulty in identifying individuals of different emerging social status. Eventual dominants were more aggressive towards subordinates in groups of unrelated males as a result of an earlier rise in aggression towards adult levels, but relatedness within groups did not affect adult levels of aggression per se. While relatedness did not affect the amount of social investigation by eventual dominants, eventual subordinates spent much more time investigating both dominants and each other in groups of relatives, with the result that the usual asymmetry in social investigation between dominants and subordinates failed to emerge. Mice in unrelated groups spent more time investigating the substrate and there was a significant three-way interaction in substrate investigation between relatedness, eventual social status and time post-weaning. The results support the idea that kin-biased social responses in mice may arise incidentally from the social structure and olfactory communication system of house mice rather than through kin discrimination. © 1994 The Association for the Study of Animal Behaviour.