The evolutionary consequences of sexual selection and sexual conflict are epitomized in the hamadryas baboon, a species characterized by strong sexual dimorphism and intense male–male competition. Hamadryas males coerce individual females into reproductively exclusive one‐male units via aggressive takeovers, and infants involved in such takeovers are at least four times more likely to be killed (or otherwise die) after takeovers compared to other times. Here we examine female reproductive state before and after takeovers to further investigate the determinants of takeovers and their impact on female reproduction. Our data set consists of 162 takeovers over a period of 20 years in a population of wild hamadryas baboons at Filoha, Ethiopia. Results show that, in contrast to their polygynandrous relatives, hamadryas males show no bias with regard to female reproductive state at the time of the takeover, but are more likely to take over nulliparous compared to multiparous females. In addition, these results reinforce previous findings demonstrating the high likelihood of infant loss after hamadryas takeovers and suggest that females may use an additional strategy of pregnancy termination to curtail investment in offspring that are very likely to die anyway. Thus, hamadryas males may target females with high future reproductive value and hamadryas females may employ counterstrategies to help mitigate the effects of sexual coercion and infanticide on their own fitness.
Pregnancy failure represents a major fitness cost for any mammal, particularly those with slow life histories such as primates. Here, we quantified the risk of fetal loss in wild hybrid baboons, including genetic, ecological, and demographic sources of variance. We were particularly interested in testing the hypothesis that hybridization increases fetal loss rates. Such an effect would help explain how baboons may maintain genetic and phenotypic integrity despite interspecific gene flow.
We analyzed outcomes for 1020 pregnancies observed over 46 years in a natural yellow baboon‐anubis baboon hybrid zone. Fetal losses and live births were scored based on records of female reproductive state and the appearance of live neonates. We modeled the probability of fetal loss as a function of a female's genetic ancestry (the proportion of her genome estimated to be descended from anubis [vs. yellow] ancestors), age, number of previous fetal losses, dominance rank, group size, climate, and habitat quality using binomial mixed effects models.
Female genetic ancestry did not predict fetal loss. Instead, the risk of fetal loss is elevated for very young and very old females. Fetal loss is most robustly predicted by ecological factors, including poor habitat quality prior to a home range shift and extreme heat during pregnancy.
Our results suggest that gene flow between yellow and anubis baboons is not impeded by an increased risk of fetal loss for hybrid females. Instead, ecological conditions and female age are key determinants of this component of female reproductive success.
- Award ID(s):
- 2018897
- NSF-PAR ID:
- 10390535
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- American Journal of Biological Anthropology
- Volume:
- 180
- Issue:
- 4
- ISSN:
- 2692-7691
- Page Range / eLocation ID:
- p. 618-632
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
-
more » « less
Abstract Objectives In many taxa, adverse early‐life environments are associated with reduced growth and smaller body size in adulthood. However, in wild primates, we know very little about whether, where, and to what degree trajectories are influenced by early adversity, or which types of early adversity matter most. Here, we use parallel‐laser photogrammetry to assess inter‐individual predictors of three measures of body size (leg length, forearm length, and shoulder‐rump length) in a population of wild female baboons studied since birth.
Materials and Methods Using >2000 photogrammetric measurements of 127 females, we present a cross‐sectional growth curve of wild female baboons (
Papio cynocephalus ) from juvenescence through adulthood. We then test whether females exposed to several important sources of early‐life adversity—drought, maternal loss, low maternal rank, or a cumulative measure of adversity—were smaller for their age than females who experienced less adversity. Using the “animal model,” we also test whether body size is heritable in this study population.Results Prolonged early‐life drought predicted shorter limbs but not shorter torsos (i.e., shoulder‐rump lengths). Our other measures of early‐life adversity did not predict variation in body size. Heritability estimates for body size measures were 36%–67%. Maternal effects accounted for 13%–17% of the variance in leg and forearm length, but no variance in torso length.
Discussion Our results suggest that baboon limbs, but not torsos, grow plastically in response to maternal effects and energetic early‐life stress. Our results also reveal considerable heritability for all three body size measures in this study population.
-
more » « less
Abstract Ecoimmunological patterns and processes remain understudied in wild primates, in part because of the lack of noninvasive methods to measure immunity. Secretory immunoglobulin A (sIgA) is the most abundant antibody present at mammalian mucosal surfaces and provides an important first line of defense against pathogens. Recent studies show that sIgA can be measured noninvasively in feces and is a good marker of mucosal immunity. Here we validated a commercial ELISA kit to measure fecal IgA in baboons, tested the robustness of its results to variation in collection and storage conditions, and developed a cost‐effective in‐house ELISA for baboon fecal IgA. Using data from the custom ELISA, we assessed the relationship between fecal IgA concentrations and gastrointestinal parasite burden, and tested how sex, age, and reproductive effort predict fecal IgA in wild baboons. We find that IgA concentrations can be measured in baboon feces using an in‐house ELISA and are highly correlated to the values obtained with a commercial kit. Fecal IgA concentrations are stable when extracts are stored for up to 22 months at −20°C. Fecal IgA concentrations were negatively correlated with parasite egg counts (
Trichuris trichiura ), but not parasite richness. Fecal IgA did not vary between the sexes, but for males, concentrations were higher in adults versus adolescents. Lactating females had significantly lower fecal IgA than pregnant females, but neither pregnant nor lactating female concentrations differed significantly from cycling females. Males who engaged in more mate‐guarding exhibited similar IgA concentrations to those who engaged in little mate‐guarding. These patterns may reflect the low energetic costs of mucosal immunity, or the complex dependence of IgA excretion on individual condition. Adding a noninvasive measure of mucosal immunity will promote a better understanding of how ecology modulates possible tradeoffs between the immune system and other energetically costly processes in the wild. -
more » « less
Abstract Objectives Interbirth intervals (IBIs) are a key metric of female reproductive success; understanding how they are regulated by environmental, social, and demographic factors can provide insight into sources of variance in female fitness.
Materials and Methods Using 36 years of reproductive data on 490 IBIs for 160 wild female baboons, we identified sources of variance in the duration of IBIs and of their component phases: postpartum amenorrhea (PPA), sexual cycling, and pregnancy. We also examined how body fat and fecal hormone concentrations varied during female IBIs.
Results We found that IBIs tended to be shorter (reproduction was accelerated) when female traits and environmental variables promoted energy acquisition, but with different specific effects for different component phases of the IBI. We also found that females lost a substantial amount of body fat during PPA, indicating that PPA imposes accumulating energetic costs as it progresses. Prior to cycle resumption females began to regain body fat; body fat was stable across the cycling phase and increased throughout most of pregnancy. However, body fat scores per se were not associated with the duration of any of the component phases. Finally, we found that fecal glucocorticoid concentrations decreased as PPA progressed, suggesting a decline in energetic stress over this phase. Fecal progestogen and estrogen concentrations changed over time during sexual cycling; the direction of these changes depended on the phase of the sexual cycle (luteal versus early or late follicular phases).
Discussion Our study lends insight into the energetic constraints on female primate reproduction, revealing how female environments, changes in body fat, and steroid hormone concentrations relate to IBI duration and to reproductive readiness.
-
more » « less
Abstract As the value of Global Positioning System (GPS) technology in addressing primatological questions becomes more obvious, more studies will include capturing and collaring primates, with concomitant increased risk of adverse consequences to primate subjects. Here we detail our experiences in capturing, immobilizing, and placing GPS collars on six olive baboons (
Papio anubis ) in four groups and 12 vervet monkeys (Chlorocebus pygerythrus ) in five groups in Kenya. We captured baboons with cage traps and vervets with box traps, immobilized them, and attached GPS collars that were to be worn for 1 year. Adverse consequences from the trapping effort included incidental death of two nonsubjects (an adult female and her dependent infant), temporary rectal prolapse in one baboon, superficial wounds on the crown of the head in two vervets, and failure to recapture/remove collars from two baboons and two vervets. Obvious negative effects from wearing collars were limited to abrasions around the neck of one vervet. A possible, and if so, serious, adverse effect was greater mortality for collared adult female vervets compared with known uncollared adult female vervets, largely due to leopard (Panthera pardus ) predation. Collared animals could be more vulnerable to predation because trapping favors bolder individuals, who may also be more vulnerable to predation, or because collars could slow them down or make them more noticeable to predators. Along with recommendations made by others, we suggest that future studies diversify trapping bait to minimize the risk of rectal prolapse, avoid capturing the first individuals to enter traps, test the movement speeds of collared versus noncollared animals, include a release system on the collars to avoid retrapping failure, and publish both positive and negative effects of capturing, immobilizing, and collaring.
