Faecal parasites increase with age but not reproductive effort in wild female chimpanzees

Abstract

Energy investment in reproduction is predicted to trade off against other necessary physiological functions like immunity, but it is unclear to what extent this impacts fitness in long-lived species. Among mammals, female primates, and especially apes, exhibit extensive periods of investment in each offspring. During this time, energy diverted to gestation and lactation is hypothesized to incur short and long-term deficits in maternal immunity and lead to accelerated ageing. We examined the relationship between reproduction and immunity, as measured by faecal parasite counts, in wild female chimpanzees ( Pan troglodytes schweinfurthii ) of Kibale National Park, Uganda. While we observed higher parasite shedding (counts of eggs, cysts and larvae) in pregnant chimpanzees relative to cycling females, parasites rapidly decreased during early lactation, the most energetically taxing phase of the reproductive cycle. Additionally, while our results indicate that parasite shedding increases with age, females with higher fertility for their age had lower faecal parasite counts. Such findings support the hypothesis that the relatively conservative rate of female reproduction in chimpanzees may be protective against the negative effects of reproductive effort on health. This article is part of the theme issue ‘Evolution of the primate ageing process’.

Collaboration enhances career progression in academic science, especially for female researchers

“…For example, a focal author with a positive ‘adjusted network size’ score would have more unique co-authors than expected, given their number of publications. Note that this residual regression approach [ 26 , 46 ] is not the same as the much criticized ‘regression of residuals' practice [ 47 ], since here we regress the predictors, rather than the response variable. For comparison, analyses using unadjusted metrics of collaboration behaviour are included in the electronic supplementary material, appendix 1.…”

“…Here we borrow concepts from studies testing how sociality relates to fitness and survival in non-human animals to investigate how collaboration patterns may influence career progression. For many species, interacting with peers is a crucial component of lifetime fitness [ 26 , 27 ] and lifespan [ 27 ]. Group-level cooperation improves acquisition of resources (i.e.…”

Insights from evolutionarily relevant models for human ageing

“…In this volume, Jasienska [104] advocates for evolutionarily informed approaches to design more powerful studies of the health effects of reproduction, including more realistic assessments of reproductive effort. However, using detailed measures of reproductive effort, Phillips et al [92] found that wild chimpanzee females experienced only transient increases in faecal parasites during pregnancy, and high fertility predicted lower, not higher parasitism with age. This is surprising because, unlike humans, chimpanzees do not receive support from others to raise their offspring, suggesting instead that they may have effective strategies to resist the trade-offs between reproduction and health.…”

“…Two other papers translate clinical approaches to frailty to field conditions, examining ecologically relevant measures of physical performance in wild chimpanzees [90] and African foragers and pastoralists [91]. Other papers test for immunosenescence, which is difficult to measure directly in wild primates, but is detectable through its functional outcomes: age-related increases in parasitic [92] and viral infections [93]. Others have taken the opposite approach of dissecting complex phenomena like cognitive [94,95]), neurobiological [96] and skeletal ageing [97] to examine whether they result from common mechanisms across species.…”

“…The contributions in this volume highlight extensive similarities in the ageing processes between humans and other primates across a variety of domains. For example, several contributions demonstrate shared patterns of immunosenescence, both in its specific regulatory mechanisms [64] and its effects on infectious disease burden in the wild [92,93]). While the process of immunosenescence in human ageing is well recognized, the role of infectious disease in driving late-age mortality has diminished in industrialized nations relative to the role of degenerative diseases.…”