The costs of competition: injury patterns in 2 Asian colobine monkeys

Abstract

Aggression rarely escalates to physical conflict because doing so puts individuals at risk of injury. Escalation only pays off when the potential benefits outweigh the potential costs, that is, when resources critical to fitness are at stake. Here, we investigated the occurrence of injury in 2 Asian colobine species: Nepal gray langurs (Semnopithecus schistaceus) and Phayre’s leaf monkeys (Trachypithecus phayrei crepusculus). In both species, younger individuals are higher-ranking and might have greater incentive to fight. However, Nepal gray langurs have a strict breeding season, which may magnify male mating competition, and Phayre’s leaf monkeys, unlike Nepal gray langurs, have female-biased dispersal, which may increase female injury risk during subadulthood. Using long-term data on observed injuries (Nepal gray langurs: n = 208; Phayre’s leaf monkeys: n = 225), we modeled the monthly occurrence of injury (Y/N) and found that males received more injuries than females in both species. Also, subadults generally experienced frequent injury, as young individuals likely face challenges when competing for group membership and/or establishing rank. In Nepal gray langurs, males received 3 times more injuries during the mating season, suggesting strong competition for mates during this period, and females experienced more injuries before conception, suggesting competition to meet the nutritional requirements for reproduction. Unexpectedly, females in smaller groups received more injuries in Nepal gray langurs. Overall, these results indicate that injuries are most likely when fighting may aid in establishing group membership, achieving high rank, and reproducing. Future research should investigate the influence of injuries on fitness outcomes.

Behavioral and physiological responses to instability in group membership in wild male woolly monkeys (Lagothrix lagotricha poeppigii)

“…In other nonhuman primates integrating individuals of the dispersing sex have been found to be more likely to be injured (Feder et al, 2019;MacCormick et al, 2012). In our study, we also observed injuries to some of the integrating males, although there were too few instances to include these observations formally in our models.…”

Gut microbiome, diet, and conservation of endangered langurs in Sri Lanka

“…These outcomes may be linked to differences in habitat and dietary specialization. Limited data suggest that gray langurs may spend more time on terrestrial substrates (Feder, Lu, Koenig, & Borries, 2019; Hladik, 1977), and consume a more diverse diet compared to purple‐faced langurs (Hladik, 1977), which are more strictly arboreal and folivorous. Accordingly, gray langurs have a less specialized gut (reduced stomach and expanded large intestine ) compared to purple‐faced langurs (Chivers & Hladik, 1984).…”

Effects of local versus global competition on reproductive skew and sex differences in social dominance behaviour

“…Concerning sex differences in contest damage, there are data for primate species showing that males receive more injuries than females [43]. Most likely, similar results could be found in many social species.…”