The immune performance of wild capuchin monkeys declines when the animals experience warmer temperatures, and younger monkeys appear to be particularly vulnerable to heat, according to a University of Michigan study.
UM anthropology doctoral student Jordan Lucore examined how the immune systems of wild monkeys in Costa Rica were affected by temperature. Lucore and a team of researchers found that when the monkeys experienced about two weeks of warmer temperatures—86 degrees Fahrenheit—the generalized performance of their immune systems declined. This is the part of the immune system that is activated once the body senses a threat.
Their findings, published in Science Advances, were a surprise, Lucore said. Scientists expect endothermic animals—animals that can regulate their body temperature, such as mammals—to be able to protect themselves from temperature fluctuations because they can maintain a constant body temperature.
We think this has implications for understanding the effects of climate change because we see this unlikely relationship between the immune system and temperature in this particular kind of study, and we see it at much lower temperatures than expected. Eighty-six degrees Fahrenheit isn’t that hot.’
Jordan Lucore, UM anthropology doctoral student
For the study, Lucore examined a population of wild white-faced capuchins in Costa Rica’s Taboga Forest Reserve. The Capuchinos de Taboga research project, launched in 2017, focuses on the cognition, endocrinology and behavior of these primates. The project is co-directed by Jacinta Beehner, UM professor of anthropology and psychology. Thore Bergman, professor of psychology at UM. and Marcela Benítez, professor of anthropology at Emory University, who are all co-authors of the study.
“Capuchins are considered a generalist species because they live in many different places with different climates and different ecologies. They are successful generalists,” Lucore said. “That was another disturbing thing about the results: I can’t believe we’re seeing this in capuchins. They’re pretty resilient.”
Studying the immune system can be invasive: Biomarkers are usually found in blood serum, which can only be extracted by invasive means. But Lucore looked at a biomarker called neopterin, which can be measured in urine.
The researchers used a “clean capture” method to collect the urine. Urine that lands on the ground or other leaves often can’t be used because it can be contaminated, Lucore said. Taking care not to push the animals or get too close, the researchers watched the monkeys, which are habituated to human presence, until they urinated. The researchers then collected the urine using a basket wrapped in plastic attached to a stick. Field researchers at the site can individually identify each monkey to track which urine samples belong to specific individuals.
Lucore measured the amount of neopterin in the urine and modeled the temperature in the days and weeks before the urine was collected. The researchers found that immune performance decreased when the monkeys experienced two weeks of high temperatures. They also saw that younger monkeys had the strongest effect on immune performance.
“We found that the immune system of young people can be particularly affected by temperature compared to other age groups,” Lucore said. “This is especially important for potential health and fitness outcomes because when you’re young, you’re relying on your generalized immune system. Your adaptive immune system hasn’t developed yet.”
The adaptive immune system is the component of the immune system that recognizes specific pathogens – something that takes time, up to several years, for young animals to develop.
Lucore said researchers don’t yet know if this has long-term effects on wildlife health. Long-term studies will need to examine multiple generations to determine whether the monkeys’ reduced immune performance leads to poorer health or reproductive outcomes. Lucore also said the results may be difficult to apply to humans, but they can tell us something about how climate change is affecting wildlife populations.
“Climate change is happening. It’s going to affect anyone living on Earth in ways you might not expect, and especially those fundamental systems that we need to survive,” Lucore said. “The fact that a graduate student like me can go out there and collect relatively short-term data and find strong evidence that temperatures affect the physiology of wild animals — I think that’s a really important thing to keep in mind.” .
The Capuchinos de Taboga field team, namely authors Amy White, Lorena Sinclair, Vasco Alexandre Martins, Sarah Kovalaskas, and Juan Carlos Ordoñez, were instrumental in the study. Co-author Andrew Marshall, UM professor of anthropology and ecology and evolutionary biology, provided critical analysis and interpretation of the study.
Source:
Journal Reference:
Lucore, JM, et al. (2024). High temperatures are associated with reduced immune system performance in a wild primate. Advances in Science. doi.org/10.1126/sciadv.adq6629.
