Dear enemies or nasty neighbors? Causes and consequences of variation in the responses of group-living species to territorial intrusions

Christensen, Christa Lykke; Radford, Andrew N.

doi:10.1093/beheco/ary010

Cited by 106 publications

(114 citation statements)

References 114 publications

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“…Dear Enemy Effect: When an individual responds more aggressively to a territorial incursion from a stranger than to an incursion from an individual with a neighboring territory …”

Section: Glossarymentioning

confidence: 99%

“…Individual behavior in intergroup encounters is flexible, following a continuum from aggressive to tolerant, and this flexibility reflects the local environment (e.g., the patchiness of resources, seasonality in resource availability, species' diet breadth), the qualities and condition of the interacting individuals (e.g., sex, resource access, rank, the reproductive status of each), and features of the interacting groups (e.g., the balance of power between the two, the presence and number of estrous females in one or the other). However, despite evidence of this behavioral flexibility, much of the existing literature on intergroup behavior in primates emphasizes the release of selection pressures favoring aggression (e.g., the Dear Enemy Effect), which allows for either “random” or tolerant encounters (Figure ); for example, other reviews have provided thorough treatment of the selection pressures favoring (or disfavoring) aggressive intergroup behavior in nonhuman primates and in humans . Our approach differs in that we focus on individual‐level selection pressures that, given selection pressures disfavoring intergroup aggression, favor intergroup encounter and association over random encounter.…”

Section: Introductionmentioning

confidence: 99%

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The evolution of intergroup tolerance in nonhuman primates and humans

Pisor

Surbeck

2019

Evolutionary Anthropology

106

143

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Primate individuals use a variety of strategies in intergroup encounters, from aggression to tolerance; however, recent focus on the evolution of either warfare or peace has come at the cost of characterizing this variability. We identify evolutionary advantages that may incentivize tolerance toward extra‐group individuals in humans and nonhuman primates, including enhanced benefits in the domains of transfer, mating, and food acquisition. We highlight the role these factors play in the flexibility of gorilla, chimpanzee, bonobo, and human behavior. Given humans have an especially broad range of intergroup behavior, we explore how the human foraging ecology, especially large spatial and temporal fluctuations in resource availability, may have selected for a greater reliance on tolerant between‐community relationships—relationships reinforced by status acquisition and cultural institutions. We conclude by urging careful, theoretically motivated study of behavioral flexibility in intergroup encounters in humans and the nonhuman great apes.

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“…Dear Enemy Effect: When an individual responds more aggressively to a territorial incursion from a stranger than to an incursion from an individual with a neighboring territory …”

Section: Glossarymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The evolution of intergroup tolerance in nonhuman primates and humans

Pisor

Surbeck

2019

Evolutionary Anthropology

106

143

View full text Add to dashboard Cite

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“…Despite the growing number of single-species studies on IGEs in nonhuman primates, some qualitative reviews and theoretical frameworks on the topic (Kitchen and Beehner 2007;Radford et al 2016;Christensen and Radford 2018), there are very few comparative quantitative tests of group-and individual-level factors affecting IGE individual participation and outcome . In light of the large intra-and interspecific differences observed in the social behavior of primates and of the over-/underrepresentation of some species in the literature, testing whether IGEs are affected by similar factors (e.g., dominance status or sex) across primate populations and species is of primary importance.…”

mentioning

confidence: 99%

Effect of Group Size and Individual Characteristics on Intergroup Encounters in Primates

et al. 2020

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Intergroup encounters are common in nonhuman primates and can vary from affiliative to aggressive. We extracted data from the literature to test five different hypotheses: 1) where there are group size differences between opposing groups, whether the larger group is more likely to win an intergroup encounter than the smaller group; 2) whether the likelihood of a group engaging in aggressive intergroup encounters increases with group size; and 3-5) whether dominant, older individuals, and/or males are more likely to participate aggressively in intergroup encounters than subordinate, younger individuals and/or females. Our data set comprised 52 studies on 31 primate species (3 lemur species, 5 New World monkeys, 19 Old World monkeys, and 4 apes). We found that the larger group is more likely to win an encounter against a smaller group than vice versa. We found no significant relationship between group size and propensity to be aggressive during intergroup encounters. We found weak/no support for the effect of age, dominance rank, and sex on the frequency of aggression displayed toward outgroup individuals during intergroup encounters. Species-and population-specific differences in inter-and intragroup competition and in the degree of the unequal distribution of resources across group members may explain why age, dominance rank, and sex are not strong predictors of aggression during intergroup encounters.

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“…Contests between rival groups are commonplace across taxa from insects to primates (Batchelor & Briffa 2011;Hardy & Briffa 2013;Kitchen & Beehner 2007;Radford 2003;Thompson et al 2017) and nonhuman between-group conflict parallels the human scenarios discussed by D&G in many respects. For instance, fighting usually arises over a resource (e.g., food, mates, territory) already held by one group (Christensen & Radford 2018;Kitchen & Beehner 2007), and so there is an inherent role asymmetry between attackers (seeking to gain the resource) and defenders (seeking to protect that resource from usurpation). For a given pair of groups, especially in territorial species where contests between neighbours are common, which group is attacking and which is defending can change across time (birds: Radford & du Plessis 2004;mongooses: Thompson et al 2017;primates: Wilson et al 2012), and repeated interactions can influence subsequent behaviour even in the absence of recent conflict (Radford 2011).…”

Section: Introductionmentioning

confidence: 99%