When temperatures rise, the immune responses of wild capuchin monkeys suffer. This research highlights how climate change could affect animal health.
A University of Michigan study reveals that wild capuchin monkeys’ immune responses weaken in warmer temperatures, with younger monkeys being especially affected.
Jordan Lucore, a doctoral student in anthropology at U-M, explored how temperature influences the immune systems of wild monkeys in Costa Rica. Lucore and the research team discovered that the performance of the monkeys’ generalized immune system dropped after about two weeks of exposure to temperatures around 86 degrees Fahrenheit. This immune response is the first line of defense activated by the body when it detects a threat.
Lucore described their findings, published in Science Advances, as unexpected. Usually, scientists assume that endothermic animals — those like mammals that can regulate their body temperature — can better cope with temperature changes because they maintain a stable body temperature.
“These results could provide insights into how climate change impacts wildlife,” Lucore noted, “because we are observing an unusual connection between immune function and temperature in these monkeys at levels lower than anticipated. Eighty-six degrees Fahrenheit is not excessively hot.”
The study focused on a community of white-faced capuchins living in the Taboga forest reserve in Costa Rica. Initiated in 2017, the Capuchinos de Taboga Research Project investigates these primates’ cognitive abilities, hormonal systems, and behaviors. It is co-directed by Jacinta Beehner, a U-M professor of anthropology and psychology; Thore Bergman, also a U-M professor of psychology; and Marcela BenÃtez, an anthropology professor at Emory University. All co-directors contributed to the study.
“Capuchins are known as generalist species because they thrive in various environments with differing climates and ecosystems. Their adaptability is noteworthy,” Lucore explained. “This makes the findings particularly concerning; it’s surprising to see such effects in capuchins, which are generally quite resilient.”
Studying immune systems typically involves invasive methods, as necessary biomarkers are usually found in blood. However, Lucore assessed a biomarker called neopterin present in urine.
The research team employed a “clean catch” technique to obtain urine samples, as urine that lands on the ground risks contamination. By carefully observing the monkeys — which are accustomed to human presence — until they urinated, the researchers collected samples using a plastic-wrapped basket on a stick. Researchers could identify individual monkeys to match urine samples to specific individuals.
Lucore analyzed the amount of neopterin in the urine and correlated it with temperature data from the days and weeks prior to sample collection. Results indicated a decrease in immune performance during periods of elevated temperatures over two weeks. Additionally, younger monkeys demonstrated the most significant decline in their immune responses.
“Our findings suggest that the immune systems of younger monkeys may be particularly sensitive to temperature changes compared to older age groups,” Lucore mentioned. “This is crucial for their health because young monkeys depend on their generalized immune system, as their adaptive immune systems have not fully developed yet.”
The adaptive immune system is responsible for recognizing specific pathogens, a process that can take several years to fully mature in young animals.
Lucore added that it remains unclear whether these effects have lasting health implications for wildlife. Future long-term studies are necessary to track multiple generations and determine if reduced immune performance leads to poorer health or reproductive success. While the results might not directly translate to humans, they shed light on how climate change is affecting wild animal populations.
“Climate change is a reality affecting all life on Earth in unexpected ways, especially fundamental systems vital for survival,” Lucore pointed out. “It’s significant to note that a graduate student can gather relatively short-term data and uncover strong evidence linking temperature changes to the physiology of wild animals.”
The contributions of the Capuchinos de Taboga team members, particularly co-authors Amy White, Lorena Sinclair, Vasco Alexandre Martins, Sarah Kovalaskas, and Juan Carlos Ordoñez, were essential to this study. Co-author Andrew Marshall, a professor of anthropology and ecology and evolutionary biology at U-M, provided vital analysis and interpretation of the results.
