Correlates of hormonal modulation in mantled howler monkey males,Alouatta palliata

Abstract

Objectives: The study of hormone modulation may offer important insight into the responses of individuals to environmental challenges. Here we studied C-peptide, thyroid hormone (T3), glucocorticoid (GC), and testosterone (T) metabolites of mantled howler males to assess: 1) correlations among hormones; 2) individual and temporal variation in hormone concentrations; and 3) the influence of ecological, climatic, behavioral, social, and reproductive factors on hormone variation.Methods: We studied 10 adult males at La Flor de Catemaco (Mexico) from January 2012 to December 2016. We collected information on food availability; ambient temperature; time budgets; male involvement in mating, agonistic interactions, and interactions with extragroup males. We analyzed C-peptide concentrations in urine samples and T3, GC, and T in fecal samples.Results: C-peptide was negatively correlated with other hormones, whereas T3, GC, and T were positively related. Hormonal variation was unrelated to individual or yearly differences. Food availability was positively related to C-peptide and T3, and negatively related to GC. Involvement in mating was positively related to T3 and T, whereas the rate agonistic interactions was positively related to GC and T. The rate of interactions with extragroup males was positively related to T. When males mated, the increase in C-peptide and the decrease in GC with increasing food availability were less notable.Conclusions: Hormonal variation in mantled howler monkey males is generally stable, but it is influenced by several factors. Our results offer a broad picture of the hormonal modulation of mantled howler monkey males in response to diverse challenges.

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

“…Using fecal T3 data, supporting comparative evidence is now available from several species of NHPs (Chen et al, 2021;Gesquiere et al, 2018;Thompson et al, 2017). Interestingly, this research and other work with NHPs (Dias et al, 2021) also demonstrates a positive relationship between fecal T3 levels and male mating effort, a finding that provides comparative evidence for influence of T3 on energy allocation specifically to male reproduction.…”

Noise intensity modulates the responses of mantled howler monkeys to anthropophony

“…After the end of the playback experiments, we followed groups for the rest of the day. If before, during, or after the experiments we observed any of the following events, which are stimuli with the potential to affect mantled howler monkey behavior and physiology, we discarded the experiment and rescheduled it: aggression (Dias et al, 2017; n = 1 experiment); noise produced by aerial traffic, human voice (not produced by researchers), and tools/machinery (e.g., chainsaw, lawnmower: Gómez‐Espinosa et al, 2022; n = 8 experiments); mating (Dias et al, 2022; n = 1 experiment). All experiments were conducted under similar environmental conditions: no rain, absent to gentle wind (Beaufort Scale categories 0−2), mean SPL of 40.1 ± 2.1 dB.…”

“…Glucocorticoid hormones are released by the hypothalamo-pituitaryadrenocortical axis in response to psychological and energetic demands (Sapolsky et al, 2000). We have previously demonstrated that the fecal concentrations of glucocorticoid metabolites (fGCM) of mantled howler monkeys are responsive to social, ecological, and anthropogenic challenges (e.g., Cañadas-Santiago et al, 2020;Dias et al, 2017Dias et al, , 2022Gómez-Espinosa et al, 2014). Furthermore, there is a ca.…”