Stress That Saves: How Capuchin Monkeys Survived a Devastating Drought
A Surprising Link Between Stress Hormones and Survival in Wild Primates
Stress has long been viewed as the enemy of health in humans. But for wild animals, the story is more nuanced. A recent study of capuchin monkeys in Costa Rica, published in Science Advances1, suggests that stress may sometimes hold the key to survival. The findings reveal how a strong hormonal response to adversity helped certain monkeys endure the extreme drought conditions of a severe El Niño event.
Surviving El Niño: A Natural Experiment
From 2014 to 2016, a powerful El Niño event caused a catastrophic drought across Central and South America. In Costa Rica’s Lomas Barbudal Biological Reserve, the consequences were stark: the population of white-faced capuchin monkeys (Cebus capucinus) faced significant mortality due to food and water scarcity.
But this tragedy offered scientists a rare opportunity. For decades, researchers with the Lomas Barbudal Monkey Project, led by Susan Perry of UCLA, had tracked the health and behavior of this monkey population. When the drought struck, they were uniquely positioned to compare the physiological profiles of monkeys that survived with those that did not.
The Role of Stress Hormones in Survival
The study centered on cortisol, a stress hormone released during periods of adversity. Using data collected over years, the team measured how individual monkeys’ cortisol levels spiked during earlier environmental challenges. Their analysis revealed a striking trend: monkeys with a stronger hormonal response to stress were far more likely to survive the drought.
“The stress response evolved to help us mobilize the energy we need to get through challenges,” explained study co-author Sofia Carrera of Northwestern University.
This “fight or flight” mechanism, which allows animals to prioritize survival over other physiological processes, appears to have been especially beneficial during the El Niño event.
Stress in Animals vs. Humans
In humans, stress is often associated with chronic health problems, from cardiovascular disease to anxiety disorders. U-M professor Jacinta Beehner, another lead author, highlighted the stark contrast between how humans and wild animals experience stress.
“Wild animals face acute, life-threatening challenges, like escaping predators or enduring drought. In those situations, the stress response helps them survive,” Beehner explained. “But in humans, chronic stress from modern issues like mortgages or job insecurity often wears down our systems instead of helping us.”
For the capuchins, a reactive stress response allowed them to reallocate energy toward immediate survival needs, like finding food and water. This adaptability proved crucial as resources dwindled.
Long-Term Impacts and Conservation Implications
The study sheds light on how primates—and potentially other wild animals—respond to environmental stressors. It also raises important questions about conservation. Climate change is expected to increase the frequency and severity of droughts, putting more pressure on wildlife populations.
By understanding the physiological mechanisms that promote resilience, scientists can better predict which species or individuals may be more vulnerable to environmental change.
“This research highlights the importance of studying stress in a broader ecological context,” said Beehner. “It’s not just about how animals cope in the moment, but also about the long-term implications for their populations.”
A Glimpse Into the Future of Stress Research
The findings open new avenues for research into the evolutionary role of stress. Could similar patterns be observed in other primates, or even in early human populations? The study also invites a deeper exploration of how chronic stress in humans diverged from its original purpose as an adaptive survival mechanism.
For now, the capuchin monkeys of Lomas Barbudal provide a poignant reminder of nature’s capacity for resilience—and of the delicate balance required to survive in an unpredictable world.
Related Research
Sapolsky, R. M. (2004). “Why Zebras Don’t Get Ulcers.” Holt Paperbacks. A foundational work exploring the biology of stress in animals and humans.
ISBN: 9780805073690Wingfield, J. C., & Sapolsky, R. M. (2003). “Reproduction and Resistance to Stress: When and How.” Journal of Neuroendocrinology, 15(8), 711–724.
DOI: 10.1046/j.1365-2826.2003.01033.xRomero, L. M., & Wingfield, J. C. (2016). “Tempests, Poxes, Predators, and People.” Oxford University Press. Examines how animals cope with environmental stress.
ISBN: 9780195366690
These studies complement the capuchin research by deepening our understanding of stress as both a biological tool and a potential liability, depending on the context.
Carrera, S. C., Godoy, I., Gault, C. M., Mensing, A., Damm, J., Perry, S. E., & Beehner, J. C. (2025). Stress responsiveness in a wild primate predicts survival across an extreme El Niño drought. Science Advances, 11(4). https://doi.org/10.1126/sciadv.adq5020