Abstract
The study of free-living animal populations is necessary to understand life history trade-offs associated with immune investment. To investigate the role of life history strategies in shaping proinflammatory cell-mediated immune function, we analyzed age, sex, and reproductive status as predictors of urinary neopterin in 70 sexually mature chimpanzees (Pan troglodytes) at Ngogo, Kibale National Park, Uganda. In the absence of clinical signs of acute infectious disease, neopterin levels significantly increased with age in both male and female chimpanzees, as observed in humans and several other vertebrate species. Furthermore, males exhibited higher neopterin levels than females across adulthood. Finally, females with full sexual swellings, pregnant females, and post-reproductive females, the oldest individuals in our sample, exhibited higher neopterin levels than lactating females and cycling females without full swellings. Variation in females’ neopterin levels by reproductive status is consistent with post-ovulatory and pregnancy-related immune patterns documented in humans. Together, our results provide evidence of ample variation in chimpanzee immune activity corresponding to biodemographic and physiological variation. Future studies comparing immune activity across ecological conditions and social systems are essential for understanding the life histories of primates and other mammals.
Highlights
The study of free-living animal populations is necessary to understand life history trade-offs associated with immune investment
Unravelling these complex interactions requires that we study organisms within the ecological conditions to which they are adapted. Ecoimmunology[5], in which the immune system is understood in the light of evolutionary and ecological pressures, prioritizes the study of free-ranging, genetically diverse, and energetically limited populations exposed to an array of naturally occurring pathogens
Following prior r esearch[50], we conducted two additional post-hoc tests to further test the importance of sample size and determine if agerelated effects were consistent across the adult lifespan
Summary
The study of free-living animal populations is necessary to understand life history trade-offs associated with immune investment. Studies of immunosenescence in wild nonhuman mammals remain relatively rare[21], age-related increases in inflammatory biomarkers have been observed in several free-living mammal populations, including those of roe deer (Capreolus capreolus)[22], Soay sheep (Ovis aries)[23], and mandrills (Mandrillus sphinx)[24], as well as a nonindustrialized human p opulation[7]. These results suggest that inflammaging is more widespread than previously thought
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