Grooming and the value of social relationships in cooperatively breeding meerkats

In social mammals, grooming is used not only for hygienic purposes; it also serves social functions. We examined the grooming patterns of dominant males in groups of cooperatively breeding meerkats, Suricata suricatta, to test the hypothesis that the distribution of grooming reflects the value of social relationships. Grooming between dominant individuals was the most commonly observed interaction. Grooming by the dominant male was less common when the dominant female was in oestrus. Grooming between dominant males and subordinates was asymmetrical, with dominant males receiving more grooming and providing less grooming to subordinates. Because subordinate males defend the group against extragroup males, the dominant male was predicted to groom subordinate males more often than to groom subordinate females. Although the sex of a subordinate did not affect the probability of grooming occurring, dominant males groomed subordinate males for longer than they groomed subordinate females. The duration of grooming by a dominant male was longer in small groups than large groups, suggesting that grooming activity is constrained by time. In contrast, subordinates groomed dominant males for longer in larger groups, and as a result, the asymmetry of grooming exchanges was exaggerated in larger groups. This result is consistent with the biological market theory, which predicts that the value of subordinates is dependent on group size and that subordinates will alter grooming efforts accordingly. These results suggest that meerkat grooming serves several social functions, such as the maintenance of valuable and/or fitness-enhancing relationships.