The consequences of inbreeding for recognizing competitors

Extreme inbreeding will compromise an animal's ability to discriminate betw een individuals and, thus, assess familiarity and kinship with conspecifics . In rodents, a large component of individual recognition is mediated throu gh chemical communication. The counter-marking of competitor males' scent m arks provides a measure of discrimination between their own scent and that from other individuals. We investigated whether males in common outbred (IC R(CD-1) and TO) and inbred (BALB/c) strains of laboratory mice could recogn ize the urinary scents of other individuals by measuring their investigatio n and counter-marking responses. Dominant males of outbred strains investig ated and counter-marked scents from Ether males, whether of the same or ano ther strain. Dominant inbred BALB/c males investigated but did not counter- mark their own strain scents, counter-marking only those from another strai n. They did not use environmentally induced status differences in odours to recognize scents from other males. The inability of the inbred mice to dis criminate between their own scent marks and those of other males is likely to alter their competitive behaviour, which could influence responses in ex periments and the welfare of caged laboratory mice.