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.

Intergroup lethal gang attacks do not require fission-fusion dynamics to evolve

“…In crested macaques, infants were the most Page 14 of 23 common victim after adult females, and the most frequently killed. Intergroup infant killing during gang attacks is also common in meerkats (Dyble et al, 2019). In both, meerkats and crested macaques, larger groups tend to win intergroup encounters, with the number of pups and females, respectively, increasing the odds of displacing other groups (Dyble et al, 2019;Martínez-Íñigo, 2018).…”

“…Intergroup infant killing during gang attacks is also common in meerkats (Dyble et al, 2019). In both, meerkats and crested macaques, larger groups tend to win intergroup encounters, with the number of pups and females, respectively, increasing the odds of displacing other groups (Dyble et al, 2019;Martínez-Íñigo, 2018). Samango monkeys (Cercopithecus mitis erytharchus) (Payne et al, 2003), and possibly Diana monkeys (Cercopithecus diana) (McGraw et al, 2002) are two other species in which philopatric individuals have gang attacked an outgroup individual of their sex.…”

“…Contrary to the imbalance-of-power-hypothesis predictions, several mammal species with stable groups have been observed engaging in lethal gang attacks (Table 2 and Dyble et al, 2019;Johnstone et al, 2020). Here, we present a comprehensive and detailed account of intergroup gang attacks in a non-hominid primate species living in stable groups without fission-fusion dynamics, the crested macaque (Macaca nigra).…”

Assessment during Intergroup Contests

“…and loser effects have been inferred through movement patterns. For example, losing groups used the area in which the contest occurred less frequently [31], moved faster and further than winning groups [32], or slept closer to their territory center ( [33]; cf [34] where losers slept closer to the territory boundary). Although these behavioral changes imply a loser effect, none of these studies tested whether losing groups actually lost, or winning groups won, future contestsa key component of establishing winner or loser effects.…”

“…Although group size is the best predictor of contest success among meerkat groups, groups with pups can overcome a group size disadvantage to win the contest [33]. Groups with pups might have a motivational advantage related to resource value: winning new territory can result in more food for developing young [33].…”