Learning style predicts survival skills in young orangutans

How much knowledge a wild orangutan acquires over its long development depends on its tendencies for learning socially and individually

To the point:

• Orangutans have individual learning styles: over their 8.5-year development, infant orangutans differ from one another in how frequently they engage in social and individual learning.
• Learning style predicts skill development: infants’ social and individual learning tendencies during development predict how many food items they will have learned by the time they become independent from their mothers.
• Learning is more than simply “social” or “individual”: the study shows for the first time that social and individual forms of learning interact to shape broad skill acquisition in wild great apes.

Orangutan infants spend their first eight years with their mothers, and throughout this time, they can draw on her knowledge. After that, however, orangutans are entirely on their own. To fare well as an independent orangutan, infants need to learn many survival skills, and arguably the most important of these are feeding skills. An adult orangutan’s diet constitutes nearly 250 distinct food items, which it chooses from thousands of different options, some of them potentially toxic, in the wide maze of the rainforest. Before they set out on their own, infants must also learn how foods should be processed, and when and where foods can be found in the forest

“How do infants master this complex diet curriculum in those first years?” asks Revathe Thillaikumar, a Marie Sklodowska-Curie Actions Postdoctoral Fellow at the Max Planck Institute of Animal Behavior.

Humans offer clues. Throughout our evolutionary history, humans had to learn an immense set of skills necessary for survival across many years of development. Many of these skills, such as knowledge of new food sources or hunting techniques, are learnt from one’s culture through a complex interplay of different forms of social and individual learning.

“But until now, whether and how wild animals use different forms of learning to develop their survival-relevant skills have remained unknown,” she says.

In a new study, Thillaikumar and colleagues show that wild orangutans build their broad diet profiles through a similarly fascinating interplay of social and individual learning during infancy. The study, published in Science and led by researchers at the Max Planck Institute of Animal Behavior (MPI-AB) in Germany, in collaboration with Universitas Nasional in Indonesia, is the first to show that multiple forms of learning interact over many years to build broad, survival-relevant ecological skills in a wild great ape.

Learning by watching, and doing

Researchers agree that many animals need learning to acquire many of the skills necessary for survival in the wild. However, it is debated to what extent animals learn from others (social learning) or practicing themselves (individual learning).

Answering this is challenging, especially in long-lived species like great apes. “To really understand how these forms of learning translate into actual skills and knowledge, we needed to link learning events to concrete, measurable outcomes like diet. But because orangutans develop so slowly, there is a multi-year lag between learning and measurable behavioral change,” says Caroline Schuppli, senior author of the study and group leader at MPI-AB.

A detailed dataset

The researchers overcame this challenge by drawing on long-term data from the Suaq Balimbing research station, Gunung Leuser National Park in Indonesia, where an international team of researchers and field assistants follow wild Sumatran orangutans over the course of the animals’ lives. For the study, the team investigated data from 21 immature orangutans recorded from birth to independence at around 8.5 years of age. Across 4,700 hours of observation, they examined three key behaviors: when orangutans closely observed their mother and nearby conspecifics through a behavior called “peering” (a behavioral indicator of social learning); when they explored different items in their habitat (a behavioral indicator of individual learning); and what food items they successfully ate without help from their mothers (a measure of ecological competence).

Thillaikumar worked with theoretical statistician Paul-Christian Bürkner of TU Dortmund University to analyze just under seven thousand records of social and individual learning, keeping each animal’s history separate to determine how its learning behavior related to its eventual diet breadth. “Analyzing each individual on its own was a linchpin for our study because this allowed us to finally link the two parts that were previously unbridgeable-learning and skill development,” says Thillaikumar.

Two forms of learning

The researchers found that immature orangutans differed substantially in how much they engaged in social versus individual learning. “We were astonished by how different infants were from one another in their tendencies to learn,” adds Thillaikumar. Despite such variation, all immatures engaged in social learning more frequently than individual learning-as much as five times more frequently on average.

“Learning purely through individual exploration can be risky for a naïve orangutan, especially for immatures who are still growing and cannot afford to miss out on feeding opportunities. So the safer option may be to watch and learn from knowledgeable role models, such as their mothers” explains Schuppli.

Three-fold contribution of social learning

The team found that when infants engaged in social learning, it triggered subsequent exploration for as long as two-and-a-half hours. “Each time an infant peered, it had a prolonged, ripple effect on subsequent explorations,” says Thillaikumar. The authors wanted to pin down the effects of each of the two processes, so they considered only explorations that were independently initiated to test how individual and social learning worked together.

They found that social learning and individual learning worked in tandem over the developmental period. Infants that engaged in high rates of both forms of learning ended up with the broadest diet profiles at independence. Conversely, when both forms of learning were low, individuals ended up with the lowest diet breadth, with a three-fold difference between high and low learning of both forms.

Increased social learning could even partially compensate for low individual learning by improving diet breadth. “Social learning stepped in to do the heavy lifting, which shows us just how significant it is in the lives of great apes,” adds Thillaikumar.

The results prompt a nuanced appreciation of the mechanisms underlying great ape cultures. “It’s about more than just social or individual learning,” says Schuppli. “It’s about the interplay of complex learning mechanisms that has driven the development of a broad, highly survival-relevant cultural competence in one of our closest, living relatives in the wild. This suggests that the sophisticated cultural learning seen in humans may have deep evolutionary roots.”

Linking learning to survival

The results show that heightened learning results in broader diets, but questions remain about exactly how this advantage arises. “Are they learning about lots of items, or are they getting better at learning?” asks Thillaikumar.

The team now plans to look beyond diet breadth to determine whether greater learning also improves energy intake, and ultimately, if this actually translates into survival and reproduction.

“Questions like these can only be answered by watching animals in their natural environment from birth to death,” says co-author Sri Suci Utami-Atmoko from Universitas Nasional in Indonesia. “Long-term field studies provide the time and space to follow long-lived animals over their whole histories. For orangutans, these studies provide us with window into how culture and survival have become intertwined over evolutionary time”.