Effects of group size and contest location on the outcome and intensity of intergroup contests in wild blue monkeys

Abstract

Intergroup contests determine access to resources and influence the evolution of group living in 24 social species. Asymmetries in resource holding potential and payoffs should influence the 25 outcome and intensity of such contests. We evaluated predictors of contest outcome and intensity 26 using data collected over 40 months from 6 groups of wild blue monkeys (Cercopithecus mitis). 27 We found increased odds of winning when a group was larger than and used the contest site 28 more than its opponent, and when contests occurred closer to its home range center while farther 29 from the opponent's center. However, a larger difference in group size (across five pairs of 30 opposing groups) did not predict a greater proportion of contests won by the larger group. Some 31 evidence suggested increased odds of a draw when group sizes were more similar. Additionally, 32 contests were longer and more aggressive when groups were more similar in size and when the 33 contest site was similarly central in both groups' home ranges. Contests were also more 34 aggressive when the opposing groups' use of the contest site was more similar. Overall, 35 asymmetries in resource holding potential (i.e. group size) and/or payoffs related to the contest's 36 location influenced a group's competitive advantage, the likelihood of a draw, and the intensity 37 of intergroup contests. Although comparable data are limited, it seems clear that both types of 38 asymmetries can play a role in determining the outcome and intensity of intergroup contests, and 39 that the relative power of each may vary across species. 40 41

The role of the residence-effect on the outcome of intergroup encounters in Verreaux’s sifakas

“…In conclusion, our results support the assumption that the particular circumstances of group encounters, such as the location of the conflict, are crucial predictors for the outcome of encounters31117202241. Since the particular conditions of each encounter ought to impede the establishment of stable dominance relationships between groups, our data support the notion that the dilemma between cooperation and competition in gregarious animals occurs at the individual level3114146.…”

Stronger between-clan than within-clan contests and their ecological correlates in a non-territorial, fission-fusion species, the Asian elephant

“…2002, Koenig and Borries 2006, Chancellor and Isbell 2009, Hanya 2009) rather than on between-group contest (for example, Wilson et al . 2012, Brown 2013, Roth and Cords 2016, Pal et al . 2018).…”

“…Many studies of between-group contest have largely focused on territorial behaviour or factors affecting outcomes of the contests or their consequences for group members (for example, Cheney 1987, Markham et al . 2012, Willems and van Schaik 2015, Roth and Cords 2016, Majolo et al . 2016, Mirville et al .…”

Stronger social bonds do not always predict greater longevity in a gregarious primate

“…Variables other than the quality of social ties and rank can also influence survival in group-living animals. Large group size may enhance survival by providing benefits similar to those of maintaining particularly affiliative relationships, such as more effective vigilance for predators (Elgar, 1989;Lehtonen & Jaatinen, 2016;Roberts, 1996;van Schaik & Van Noordwijk, 1986), defense of young offspring (Grinnell & McComb, 1996;Wolff & Peterson, 1998), or defense of feeding territories (Radford & du Plessis, 2004;Roth & Cords, 2016). Nevertheless, living in larger groups may also exact costs by increasing within-group competition for food (Roberts & Cords, 2013;VanderWaal, Mosser, & Packer, 2009), or by increasing the risk of male takeovers and subsequent infanticide (Steenbeek & van Schaik, 2001).…”