Ann Arbor Times

Faced with severe drought conditions, capuchin monkeys in northwestern Costa Rica have demonstrated remarkable resilience, according to a study conducted by researchers from the University of Michigan. The study provides the first data from wild primates suggesting that a stronger stress response may enhance survival during environmental challenges.

The research focused on hormone levels in capuchins to understand how their stress response aids survival. During a severe El Niño event from 2014-2016, a drought affected Central and South America, causing significant mortality among white-faced capuchin monkeys. The Lomas Barbudal Monkey Project, led by Susan Perry of UCLA, has been studying this population since 1990. The drought served as a natural experiment for researchers to compare the stress physiology of surviving monkeys with those that did not survive.

Published in Science Advances, the findings reveal that monkeys with a robust stress reaction—marked by an increase in stress hormones—were more likely to survive the harsh El Niño conditions than those with milder responses. This conclusion remained valid even after considering other factors affecting hormone levels.

Sofia Carrera, one of the study's first authors and a postdoctoral researcher at Northwestern University, explained: “The stress response evolved to help us mobilize the energy we need to get through challenges (think of this as the ability to run from a predator),” adding that most research typically focuses on how stress hormones negatively impact health and longevity.

Jacinta Beehner, U-M professor of psychology and anthropology and lead author of the study, acknowledged the 'wear-and-tear' effect of stress on human systems leading to health issues like heart disease. However, she noted that while humans do not benefit from modern stressors such as mortgages or job insecurity, wild animals face challenges where a reactive stress response can be advantageous for survival.

“High levels of stress hormones appear to promote (rather than hinder) survival under challenging conditions when food resources are scarce,” Beehner stated.

The study was supported by additional co-authors Irene Godoy, Colleen Gault, Ashley Mensing, and Juliane Damm. They played crucial roles alongside the rest of the Lomas Barbudal Monkey Project team in executing this research.