Intergroup aggression in meerkats

Abstract

Violent conflicts between groups have been observed among many species of group living mammals and can have important fitness consequences, with individuals being injured or killed and with losing groups surrendering territory. Here, we explore between-group conflict among meerkats (Suricata suricatta), a highly social and cooperatively breeding mongoose. We show that interactions between meerkat groups are frequently aggressive and sometimes escalate to fighting and lethal violence and that these interactions have consequences for group territories, with losing groups moving to sleeping burrows closer to the centre of their territories following an intergroup interaction and with winning groups moving further away. We find that larger groups and groups with pups are significantly more likely to win contests, but that the location of the contest, adult sex ratio, and mean within-group genetic relatedness do not predict contest outcome. Our results suggest that intergroup competition may be a major selective force among meerkats, reinforcing the success of large groups and increasing the vulnerability of small groups to extinction. The presence of both within-group cooperation and between-group hostility in meerkats make them a valuable point of comparison in attempts to understand the ecological and evolutionary roots of human warfare.

Keywords: animal groups; conflict; fitness; social behaviour; violence.

Figure 1.

Escalation of meerkat intergroup interactions from initial encounter to lethal violence. The numbers in parentheses represent the number of occurrences of each change in our in dataset. Interactions typically end when one of the groups retreat. ‘Aggression’ and ‘fight’ photographs courtesy of Dominic Cram, KMP. ‘Group seen’ and ‘lethal violence’ photographs taken by M.D., KMP.

Figure 2.

Factors that determine the outcome of meerkat intergroup interactions. (a) Effects of our five predictors on the likelihood of the focal group winning an intergroup interaction and (b) predicted probability of the focal group winning an intergroup contest as a function of relative group size and of the presence of pups in the focal and opponent group.

Figure 3.

Territorial consequences of meerkat intergroup interactions (IGI). (a) Proportion of winning and losing focal groups that moved sleeping burrow in the evening after an intergroup interaction. (b) Distance moved by winning and losing groups relative to their territory centre. Positive values indicate a move away from the territory centre. Error bars show the standard error.