Infant mortality in white‐faced capuchins: The impact of alpha male replacements

Abstract

Infanticide is common in the context of alpha male replacements (AMR), particularly in groups where alpha males experience high reproductive skew and the infants are unlikely to be related to a new alpha male. We examined the relationship between the rate of infant mortality, infant age, and the occurrence and type of AMR in white-faced capuchin monkeys (Cebus capucinus imitator) of the Santa Rosa population in Sector Santa Rosa, Área de Conservación Guanacaste. Specifically, we investigated how the source of the new alpha male (coresident or extragroup) and relative aggression level during AMRs influenced infant mortality in this species. Between 1986 and 2015, we recorded 221 births in five study groups. Infants present at the time of an AMR, or born within 5.5 months following an AMR (i.e., conceived prior to AMR), experienced significantly higher mortality than those born during periods of group stability. Infant age was a significant predictor of infant survival, with the probability of surviving increasing by 0.4% for each additional day older an infant was at the time of the AMR. Infant mortality rates did not differ between AMRs by coresident males and extragroup males, possibly because the degree of relatedness between infants and new alphas did not significantly differ between coresident and extragroup AMRs. Infant mortality rates did not differ significantly between aggressive AMRs and more peaceful AMRs. Our results are consistent with predictions derived from the sexual selection hypothesis (SSH) of infanticide and suggest that future studies examine the role of testosterone as an underlying proximate mechanism for the aggression leading to this behavior. We argue that the sexual selection and generalized aggression hypotheses (GAH) of infanticide are best considered as different levels of analysis rather than competing hypotheses.

Primate life history, social dynamics, ecology, and conservation: Contributions from long‐term research in Área de Conservación Guanacaste, Costa Rica

“…In several species of primates, dominance rank (Majolo et al, 2012) (Brasington et al, 2017;Kalbitzer et al, 2017).…”

“…Risk of infanticide by adult males varies extensively among primates, and numerous research efforts to understand the variation and evolution of this behavior have been undertaken (Henzi & Barrett, 2003;Lukas & Huchard, 2014;Palombit, 2012 (Fedigan & Jack, 2013). Despite these strategies, infanticide is the leading source of infant mortality among capuchins in SSR and we have directly witnessed numerous cases (Brasington et al, 2017;Kalbitzer et al, 2017).…”

Differential impact of severe drought on infant mortality in two sympatric neotropical primates

“…In spider monkeys, gestation is 7.5 months, the average interbirth interval is 35 months, and weaning age varies from 19 to 31 months [49]. Male infanticide is a major source of infant mortality in the capuchin population at SSR [50][51][52], but it is not yet known whether male infanticide is a significant source of infant mortality in the spider monkey population. A comprehensive review of the natural history of the capuchin and spider monkey populations in SSR, including life-history traits, social structure and dynamics, and behavioural ecology, can be found in [53].…”

Group versus population level demographics: An analysis of comparability using long term data on wild white‐faced capuchin monkeys (Cebus capucinus imitator)

“…If observer presence reduces the rate of attempted takeovers by unhabituated males, then not only would we expect smaller numbers of adult and subadult males in our study populations, but there may also be reduced infanticide risk for infants, resulting in higher infant survivorship. The risk of infanticide in capuchin groups is high during group takeovers and has measurable impacts on infant mortality rates and interbirth intervals (Brasington et al, ; Fedigan, ; Kalbitzer et al, ). That our results indicate more infants per study group, but not more adult females, suggests that if the infant difference is real and not a sampling error, adult females in study groups potentially have shorter interbirth intervals than nonstudy groups, a result well worth investigating further.…”

“…These dispersal events are a dangerous time period, with a high mortality rate for both migrating and resident males (Gros‐Louis, Perry, & Manson, ; Jack & Fedigan, ). Entry into a new capuchin group is usually agonistic, and, if successful, often results in the displacement of existing group males and a significant increase in infant mortality from male‐mediated infanticide (Brasington, Wikberg, Kawamura, Fedigan, & Jack, ; Fedigan, ; Fedigan et al, ; Jack & Fedigan, ; Manson, Gros‐Louis, & Perry, ). Male capuchins continue to move between groups throughout their adult life (Wikberg et al, ).…”