, 2006; Clutton-Brock, 2009b). In others, it may reduce the risk of infanticide by other EPZ015666 cell line females. For example, in meerkats, pregnant females frequently kill infants born to other group members within 2–3 days of birth and breeding females often evict older subordinate females

from the group in the weeks before parturition, allowing them to return after their pups are several days old (Clutton-Brock et al., 1998b). Eviction frequently induces abortion in evicted females and evicting older subordinates (who are more likely to have conceived) may reduce the risk that the dominant female’s pups will be exposed to pregnant females. In addition, abortion increases the chances that subordinates will subsequently suckle pups born to the dominant female, so that an additional benefit of evicting subordinates to dominants BGJ398 mouse may be that it increases contributions to rearing their pups (Young et al., 2006).

In plural breeders, rising levels of aggression between subgroups of females in large groups can eventually cause groups to split, generating two or more separate groups with distinct home ranges. For example, in macaques, increases in group size commonly lead to increased competition between females, which eventually lead to larger groups splitting and to reductions in competition for resources (Okamoto, 2004). When groups split, they typically do so along matrilineal lines so that average levels of kinship between group members tend to increase. For example, when groups of yellow baboons split, females typically remain in the same subgroup as their close maternal kin (van Horn et al., 2007). Compared with evictions,

the immediate costs of group splitting are relatively low since individuals are not forced to leave groups alone. However, it may have substantial deferred costs if one of the new groups is forced to occupy an inadequate range or is unable to compete effectively with neighbours but, as yet, few studies have been able to assess how large such effects may be. Where potential conflict or limited resources occur between individuals of contrasting fighting ability, less-powerful individuals often benefit by avoiding conflict and allowing their opponents learn more to monopolize resources without direct conflict (Bernstein, 1981; Kaufman, 1983). Subordinates commonly either avoid the proximity of dominants or adjust their behaviour to avoid conflict as soon as they are threatened and, as a result, a high proportion of potential conflicts between group members are usually resolved without fighting. Where there are consistent differences in fighting ability or power between individuals, the avoidance of conflict by weaker individuals generates hierarchies of dominance (or submission) between group members (Rowell, 1974; Silk, 1993).