Age negatively impacts reproduction in high-ranking male rhesus macaques on Cayo Santiago, Puerto Rico

Krista M Milich,Dario Maestripieri,Angelina Ruiz-Lambides,Elizabeth Maldonado

doi:10.1038/s41598-020-69922-y

Krista M Milich, Dario Maestripieri + Show 2 more

Open Access

https://doi.org/10.1038/s41598-020-69922-y

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Abstract

Based on sexual selection theory, the reproductive potential of male primates is expected to be limited by access to fertile females. Alpha males, the highest ranking males in a social group, are predicted to have better access to mates and produce more offspring until they are no longer dominant, which usually corresponds with age. Little is known about male reproductive senescence independent of rank changes in nonhuman primates. Here, we examine variation in the reproductive success of high-ranking male rhesus macaques on Cayo Santiago. We recorded behavioral data for 21 adult males across 9 social groups during the 2013 mating season. Additionally, we used paternity data from the long-term database to determine the number of offspring each subject sired over his lifetime and during the study period. Older high-ranking males in stable groups had fewer offspring than younger high-ranking males in stable groups in 2013. The low reproductive output for the older males was not a result of lower mating effort, and reproductive output in 2013 was not predicted by total prior reproductive success. Our results provide novel evidence of post-copulatory reproductive senescence in high-ranking male nonhuman primates.

Highlights

Sexual selection theory predicts that male primates are mainly limited in their reproductive potential by access to fertile females[1]
Little is known about male reproductive senescence, or age-related declines in reproduction, independent of rank changes in primates, a large body of research literature on this topic exists for human males[7,8,9,10,11,12,13]
The focus has primarily been on female reproductive senescence, and many studies have assumed that alpha males who are seen mating frequently are producing offspring, regardless of their age[20]

Summary

Introduction

Sexual selection theory predicts that male primates are mainly limited in their reproductive potential by access to fertile females[1]. There is significant variation in the age of high-ranking males on the island, which may be facilitated by food provisioning that may provide opportunities for older males to maintain high-ranking positions more frequently than they would be able to under more ecologically stressful conditions. This pattern may be further facilitated by the succession rank system in rhesus macaques, in which males typically achieve high dominance status based on their tenure in a g roup[27] (but see28) rather than by challenges to other m ales[29]

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