Odour similarities as a basis for discriminating degrees of kinship in rodents: evidence from Mus spicilegus

To achieve odour-based kin recognition, rodents need olfactory cues that indicate kinship. Odour-genes covariance is a phenomenon by which closer genetic relationships between individuals are reflected in greater similarity in their odours. We tested odour-genes covariance among kin groups in Mus spicilegus. Using a habituation-generalization procedure designed to assess responses to similarities, we found that males (unrelated to any of the odour donors) recognized similarities in the odours of brothers (r = 0.5) when compared to an unrelated male. With the same protocol, we also found similarities between the odours of double cousins (r = 0.25) and cousins (r = 0.125). This demonstrates that kinship from siblings to cousins is reflected in odour similarity. To investigate the precision of animals' responses to odour similarities based on relatedness, we conducted similar tests using odours from males of different relatedness to the habituation odour donor. Mice responded to the similarities between odours of double cousins compared to cousins. This is a clear demonstration of the subtlety of odour-genes covariance among close kin. Mice did not, however, treat odours of brothers as similar compared to those of 'super half-brothers' (r = 0.375). We discuss the implications of these findings for differential responses based on degrees of relatedness, including kin recognition.