Climate Extremes Disrupt Social Structures and Maternal Care in White-Faced Capuchin Monkeys

Extreme climate events, such as the 2015 El Niño drought, disrupt the social structures and maternal behaviors of white-faced capuchin monkeys. According to research published in Nature Ecology and Evolution, these stressors lead to increased infant mortality and alter how monkey groups compete for limited food resources in Costa Rica’s Lomas Barbudal forest.

Why do extreme droughts change monkey behavior?

Severe resource scarcity can override fundamental biological instincts, including maternal care. During an abnormally severe drought in 2015 influenced by the El Niño–Southern Oscillation (ENSO), evolutionary anthropologist Perry from the University of California, Los Angeles observed white-faced capuchin mothers abandoning their infants. Perry reported seeing babies crying on the ground while mothers walked away, a behavior she noted was contrary to their typical devotion under normal conditions.

Perry stated that these observations highlight the limits of capuchin adaptability as climate extremes become more frequent.

How does group size affect survival during climate events?

Group size typically provides a trade-off between resource control and internal competition. Behavioral ecologist Odd Jacobson of the Max Planck Institute of Animal Behavior analyzed 33 years of geolocation data to determine how these dynamics shift during climatic extremes.

Under standard conditions, larger groups often dominate resource-rich “food patches,” such as fruiting trees. However, Jacobson found that during extreme wet or dry seasons, internal competition for food intensifies, reducing the overall foraging efficiency of the group.

The research also challenged existing assumptions about territorial dominance. While large groups usually overpower smaller ones to secure fruit-rich areas along rivers during typical dry seasons, they stopped hoarding these high-quality areas during extreme El Niño events. Jacobson suggested this may happen because the landscape becomes so uniformly poor that there are no longer specific high-quality patches for larger groups to monopolize.

Capuchins vs. Spider Monkeys: Different survival strategies

Different primate species employ distinct biological responses to survive severe droughts. Filippo Aureli, an ethologist at the Universidad Veracruzana, compared the impacts of the 2015 drought on capuchin and spider monkey populations in the Costa Rican dry tropical forest.

• White-faced Capuchins: Experienced high rates of infant mortality as mothers abandoned offspring.
• Spider Monkeys: Tended to stop reproducing during the extreme event.

Aureli noted that while these populations have held on so far, the increasing intensity of climate extremes makes their long-term viability uncertain.

What happens next for primate societies?

The unpredictability of weather patterns poses a risk to the “optimal size” of primate groups.

Researchers emphasize the necessity of baseline data to understand these shifts. Perry noted that without knowing what “normal” conditions look like, scientists cannot accurately measure the impact of the chaos currently affecting global ecosystems.

Frequently Asked Questions

How did researchers track the monkeys?

The team used a “hierarchical social relations model” combined with 33 years of geolocation data. This allowed them to predict how different monkey groups moved through the forest and where their territories overlapped.