The Evolution of Indiscriminate Altruism in a Cooperatively Breeding Mammal

Duncan, Chris; Gaynor, David; Clutton‐Brock, Tim; Dyble, Mark

doi:10.1086/703113

Cited by 26 publications

(46 citation statements)

References 72 publications

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“…For example, our model predicts that intragroup relatedness will be lower in larger groups except in cases where there is high reproductive skew among both males and females. Among our test species, this is the case for both meerkats and Damaraland mole-rats: although both species frequently live in groups of more than twenty individuals, high reproductive skew in both sexes means that the majority of individuals born in the group are siblings and mean intragroup relatedness is accordingly high at r = 0.35 for meerkats Duncan et al 2019) and r = 0.46 for Damaraland mole-rats (Burland et al 2002).…”

Section: Discussionmentioning

confidence: 99%

Contrasts in kinship structure in mammalian societies

Dyble

Clutton‐Brock

2020

Behavioral Ecology

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Comparative studies of mammals confirm Hamilton’s prediction that differences in cooperative and competitive behavior across species will be related to contrasts in kinship between group members. Although theoretical models have explored the factors affecting kinship within social groups, few have analyzed the causes of contrasts in kinship among related species. Here, we describe interspecific differences in average kinship between group members among social mammals and show that a simple mathematical model that includes the number of breeding females, male reproductive skew, and litter size successfully predicts ~95% of observed variation in average kinship between group members across a sample of mammals. Our model shows that a wide range of conditions can generate groups with low average relatedness but only a small and rather specific set of conditions are likely to generate high average levels of relatedness between their members, providing insight into the relative rarity of advanced forms of cooperation in mammalian societies.

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Section: Discussionmentioning

confidence: 99%

Contrasts in kinship structure in mammalian societies

Dyble

Clutton‐Brock

2020

Behavioral Ecology

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“…Contrary to theoretical predictions [33], we found no effect of mean within-group genetic relatedness on the outcome of intergroup aggression or of between-group genetic relatedness on the probability of aggression during an interaction. However, it is important to note that, as with the lack of kin discrimination in within-group cooperative behaviours in meerkats [35], this does not necessarily indicate that the willingness of meerkats to engage in intergroup contests has not been selected via indirect fitness benefits. Although the effect of interaction location on contest outcome was not significant, the direction of the effect was consistent with the kind of 'home territory' advantage seen in other species [32].…”

Section: Discussionmentioning

confidence: 99%

Intergroup aggression in meerkats

et al. 2019

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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.

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“…Subordinates within their natal groups may thereby also stand to gain indirect fitness benefits from defending the territory's resources (a public good) for use by relatives, and by defending the dominants themselves (and their future reproductive success) from displacement by unrelated extragroup individuals (Hatchwell, 2009). Indeed, the indirect benefits to subordinates of contributions to territorial defence are likely to be an important source of selection for the maintenance of subordinate contributions to territory defence in cooperatively breeding societies, in addition to the direct benefits that are typically the focus of public goods scenarios (Duncan et al, 2019;Gavrilets & Fortunato, 2014;Hatchwell, 2009). While we did not investigate the extent to which individual variation in inclusive fitness payoffs from investment in territorial defence explains individual variation in subordinate contributions for our focal species in this study, the lack of a sex difference in the probability that subordinates inherit the breeding position within their natal groups (Harrison et al, 2014), coupled with the likely lack of a sex difference between subordinates in the indirect benefits to be accrued from defence of the natal territory, could explain why we found no evidence here of a clear sex difference in subordinate contributions to territory defence.…”

Section: Discussionmentioning

confidence: 99%

Dominance-related contributions to collective territory defence are adjusted according to the threat

2019

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Across diverse societies, group members benefit from the cooperative maintenance of a shared territory (a public good). How such public goods are maintained has received extensive interest, yet individual contributions to cooperative territory defence remain poorly understood. Recent theory predicts that, in groups with social hierarchies, privileged individuals will contribute most to competition with rival groups as they benefit most from defence of the territory. Here, we investigated whether dominant individuals contribute more to territory defence in a group-territorial bird in which dominants monopolize within-group reproduction: the white-browed sparrow-weaver, Plocepasser mahali. Using simulated territorial intrusions, we demonstrate that dominants contributed significantly more than subordinates to territory defence. We also found that individual contributions were adjusted according to threat: males of both social classes significantly and similarly increased their contributions to defence in response to a high threat (playback of an unfamiliar pair's duet, rather than that of a neighbouring pair), which was associated with a stronger collective response by the group. Thus, while dominants contributed most as predicted by the asymmetry in benefits, subordinates did increase contributions when they were needed most (in small groups and under greater threat). Contributions by subordinates when needed most also highlights that dominants could still benefit substantially from tolerating the presence of subordinates despite their overall lower contributions. Our results show that public goods can be maintained despite unequal contributions and highlight the potential importance of context-dependent behavioural flexibility in mitigating collective action problems.

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The Evolution of Indiscriminate Altruism in a Cooperatively Breeding Mammal

Cited by 26 publications

References 72 publications

Contrasts in kinship structure in mammalian societies

Contrasts in kinship structure in mammalian societies

Intergroup aggression in meerkats

Dominance-related contributions to collective territory defence are adjusted according to the threat

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