The social function of allo-marking in the European badger (Meles meles)
Buesching CD., Stopka P., Macdonald DW.
The adaptive significance of sociality in European badgers (Meles meles) is often explained on the basis of ecological factors, but little is known about their social interactions. Here, we investigate how allo-marking of conspecifics with subcaudal gland secretions might serve as a behavioural mechanism to create a shared group-odour, thus functioning simultaneously to maintain group cohesion, and as an individual advertisement signal. The odour of subcaudal secretions, which encodes group-membership and individual-specific information, is partly generated by the bacterial flora in the subcaudal pouch. Studying the interactions of 40 different adults from two social groups, we analysed 3021 instances of allo-marking, which may be either mutual, i.e. two badgers pressing their subcaudal pouches against each other simultaneously (155 events) or sequential, i.e. one badger marking the body of another individual (2866 events). Sequential marking is significantly more frequent than mutual marking, although both occur significantly more often during the mating season and the cub-rearing season than at other times. Whereas mutual marking appears to be independent of individual-specific parameters, sequential allo-marking is strongly influenced by sex, age, and reproductive status. We propose that mutual marking generates a common group-smell by facilitating the exchange of pouch bacteria, thus aiding in group-cohesion, while sequential marking serves two purposes, to distribute the common group-smell, and to advertise individual-specific, fitness-related information. Strong correlation of the frequencies of sequential and mutual allo-marking as well as the allo-grooming behaviour between particular clusters of group members suggests the existence of sub-groups within badger groups.