Food availability influences social learning in orangutans

Food availability may be a catalyst for cultural transmission among orangutans, according to the results of a new study. Based on 18 years of observations of wild orangutans in Borneo and Sumatra, the researchers identified a relationship between an animal’s ecological environment, resource availability, and social learning behaviors.

The study was a collaborative effort by experts at the Max Planck Institute of Evolutionary Anthropology (MPI-EVA), the Max Planck Institute of Animal Behavior (MPI-AB), and the University of Leipzig. 

“Social learning includes any learning that is influenced by the observation of or interaction with another individual,” wrote the researchers.

“Culture, hence, at its most basic definition can be described as ‘socially transmitted innovations,’ and more specifically as the sum of ‘all behaviors and knowledge that are acquired and passed on within and between generations through social learning.'” 

Opportunities for social learning 

While investigating how male orangutans learn from others, the experts found that individuals who grew up in habitats with an abundance of food were more likely to pay attention to social information. 

This finding indicates that an animal’s ecological surroundings directly influence its opportunities for social learning, thereby affecting the likelihood of new behaviors becoming cultural innovations. 

“We’ve shown that animal’s ecological environment and respective resource availability has knock-on effects on an individual’s social learning opportunities, but also on their propensity for social learning over evolutionary time,” said study first author Julia Mörchen, a doctoral student at the University of Leipzig.

Nomadic lifestyle

The research was focused on adult male orangutans, a demographic chosen for their unique life history traits. Once reaching maturity, male orangutans leave their birthplaces to lead nomadic lives, constantly learning to adapt to new environments. This migrant lifestyle makes them reliant on social learning to survive.

“This means that males are like perpetual tourists, so they have to constantly learn crucial behaviors, like what food is safe to eat, from experienced locals,” explained Mörchen. To learn new skills, the migrant males watch resident orangutans in a behavior known as “peering.”

Critical insights 

In both Borneo and Sumatra, instances of migrant males peering at local residents were closely monitored. 

The researchers discovered that males were more inclined to spend time near others and engage in peering when food was abundant. This provides evidence that an animal’s environment can modulate social learning, noted the researchers. 

“When times are good, orangutans spend more time in close contact, and so there are more opportunities for social learning,” said Mörchen.

Stable food resources 

A comparison between the Sumatran and Bornean populations further underscored the study’s findings. Sumatran orangutans, living in areas with a high food supply, exhibited a higher rate of peering compared to their Bornean counterparts, who contend with less stable food resources. 

This difference persisted even after accounting for the variations in food availability, indicating a deeper, possibly inherent propensity for social learning among Sumatran males.

Study limitation

The researchers pointed out that the study cannot disentangle the mechanisms driving the difference in the propensities to attend to social information. 

“It could be the result of developmental effects, of Bornean and Sumatran orangutans growing up under different ecological conditions,” said Mörchen. “Or, it could be the result of genetic differences between the species that split approximately 674 thousand years ago, or a combination of both.”

“Our study provides a glimpse into how ecology may affect cultural transmission,” said study senior author Caroline Schuppli. “We show that availability of food modulates social learning opportunities and thus how likely new behaviors are to become cultural,” 

The study is published in the journal iScience. 

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