The white-faced capuchin monkeys (Cebus imitator) of Costa Rica are already experiencing the effects of climate change, particularly on their immune systems, according to a recent study conducted in the Taboga Forest Reserve in Guanacaste.

The findings, published in the journal Science Advances, reveal that the youngest monkeys, those under seven years old, are the most affected.

Jordan Lucore, a doctoral student in Anthropology at the University of Michigan and lead researcher on the project, emphasized the universality of climate change effects: "Climate change is already happening.

It will impact everyone on Earth in ways you might not expect," Lucore said.

The study is part of the Capuchin Research Project in Taboga, a collaborative effort between the University of Michigan, Emory University, and four Costa Rican scientists.

Since 2017, this project has been studying the cognition, endocrinology, and behavior of these primates, particularly in relation to climate change.

White-faced capuchins are known for their social nature and adaptability to various environments, from lowland coasts to mountainous regions within Costa Rica.

Juan Carlos Ordoñez Jiménez, one of the participating Costa Rican scientists, describes the species as highly social, with intricate group dynamics where each individual knows and interacts closely with its peers.

These primates are generalist species, thriving in diverse ecological settings.

However, their resilience is being tested by climate change.

The researchers focused on the innate immune system, which is the first line of defense against pathogens.

They found that approximately two weeks of warmer temperatures exceeding 30°C led to a decline in the innate immune function of the capuchins, primarily affecting the young.

This temperature increase predominantly occurs during the dry season in areas with lower forest cover, leading to thermal stress.

The study tracked 54 capuchins over a range of environmental variables.

Researchers collected and analyzed 670 urine samples over two years to measure neopterin, a marker of innate immune activity, while also noting temperature and wind conditions every 15 minutes.

This non-invasive method allowed them to monitor changes in immune response due to climatic shifts.

Ordoñez underlines that while these findings are preliminary, they highlight the urgency of long-term studies to assess the full impact on reproduction and health.

Future research aims to monitor multiple generations to understand if reduced immune performance affects survival and reproductive success.

"This doesn't mean the species will disappear, but it is a warning signal," Ordoñez concluded, stressing the need for continued monitoring.