Associations between fecal cortisol and biparental care in a pair‐living primate

Abstract

Objectives: We quantified variation in fecal cortisol across reproductive periods in Azara's owl monkeys (Aotus azarae) to examine physiological mechanisms that may facilitate biparental care. Specifically, we evaluated evidence for the explanation that owl monkeys have hormonal mechanisms to mobilize energy during periods when each sex is investing heavily in reproduction, that is, the gestation period for females and the infant care period for males.Materials and methods: Between 2011 and 2015, we monitored 10 groups of Azara's owl monkeys from a wild population in Formosa, Argentina and collected fecal samples from 26 adults (13 males, 13 females). Using enzyme-linked immunosorbent assays, we quantified fecal cortisol as a proxy for evaluating stress responses, including energetic demands, on both sexes during periods of reproduction and parental care.Results: Male cortisol was lowest during periods when they were caring for young infants (<3 months) compared with periods with older infants or no infant. Female cortisol was elevated during gestation compared with other periods. Mean fecal cortisol in both males and females was lower when an infant was present compared with when females were gestating. Discussion: Our results do not support the hypothesis that owl monkey males have elevated fecal cortisol during periods when they need to mobilize energy to provide intensive infant care. Our findings are also inconsistent with the Maternal Relief hypothesis. However, results from studies measuring fecal cortisol must be interpreted with care and alternative explanations, such as seasonal fluctuations in diet and thermoenergic demands, should be considered when drawing conclusions.

Coordinated Singing in Coppery Titi Monkeys (Plecturocebus cupreus): Resource or Mate Defense?

“…In Azara's owl monkeys (Aotus azarae), who are similar to titi monkeys in size, social system, and patterns of biparental care (infants are carried by males most of the time: Fernandez-Duque et al, 2020), fecal cortisol in both sexes was highest during gestation compared to lactation, possibly indicating higher energetic costs of gestation compared to lactation in this species (Corley et al, 2021). However, this effect might have been due to seasonality, as gestation in A. azarae takes place during the southern winter in the Argentinean Chaco, where the study was conducted (Corley et al, 2021). At our site reproduction is not strictly seasonal, with births having been recorded in July, August, and September (dry season) as well as October through February (rainy season).…”

Minimally invasive biomarkers in human and non‐human primate evolutionary biology: Tools for understanding variation and adaptation

“…In many respects, this position of leadership has emerged as a necessity for carrying out respectful and sustainable research with some of the world's most vulnerable human and comparative non‐human primate (NHP) populations. Researchers in HEB currently measure MIBs among humans and their close primate relatives in diverse contexts and in countries ranging quite literally from “A” (Argentina: e.g., Corley et al, 2021 ) to “Z” (Zimbabwe: e.g., Campbell & Mbizo, 2006 ).…”