Inbreeding and individual recognition

Nevison, C.M., Barnard, C.J., Beynon, R.J. & Hurst, J.L. (2001) Effects of inbreeding and social status on individual recognition in mice. . In: Chemical Signals in Vertebrates (Ed. A. Marchlewska-Koj, D. Muller-Schwarze & J. Lepri) pp225-232. Plenum Press, New York.

Rodents identify each other through individually unique odour cues that are determined, at least in part, by genetic differences between individuals. Individuals of highly inbred strains are unable to discriminate between each other’s volatile urinary odours when kept under identical conditions. Environmental factors such as food type and social pressure also induce changes in individual odours that are readily discriminated by other animals, stimulating differences in investigation. Investigation is not a specific test of individual recognition, however. To assess whether mice use environmentally induced differences in social status or other cues for individual recognition against a common genetic background, we examined both investigatory and counter-marking responses when odours were introduced. We also examined whether mice discriminated between familiar cagemates and unfamiliar mice of the same or a different strain when they met. Mice of outbred ICR(CD-1) and TO strains readily discriminated between individuals and their odours. Inbred mice of the BALB/c strain only countermarked urine from another strain and failed to discriminate between a familiar cagemate and an unfamiliar male of their own strain. While all males investigated subordinate male urine more than dominant male urine, environmentally induced status differences were not used for individual recognition.