Behavioural processes in social context: female abductions, male herding and female grooming in hamadryas baboons.

The formation of bonds between strangers is an event that occurs routinely in many social animals, including humans, and, as social bonds in general, they affect the individuals' welfare and biological fitness. The present study was motivated by an interest in the behavioural processes that drive bond formation in a social context of hostility, in which the incumbent partners vary greatly in physical power and reproductive interests, a situation in which individuals of many group-living species find themselves often throughout their lives. We focused on the quantitative analysis of female abductions via male aggressive herding in a nonhuman primate, the hamadryas baboon, in which intersexual bonds are known to be strong. We tested three hypotheses informed by sexual conflict/sexual coercion theory (male herding-as-conditioning and female grooming-as-appeasement) and by socioecological theory (unit size and female competition). The results supported the predictions: males resorted to coercive tactics (aggressive herding) with abducted females, and abducted females elevated the amount of grooming directed at their new unit males; in fact, they escaped from the otherwise negative effect of unit size on female-to-male grooming. These findings reveal that conflicts of interest are natural ingredients underpinning social bonds and that resorting to coercive aggression may be an option especially when partners differ greatly in their physical power.