Orangutans need years of guidance to learn what’s safe to eat

Orangutans live in forests that demand patience, memory, and long training. Young apes watch every move their mothers make.

Each gesture becomes a clue: which leaves to trust, which fruits to avoid, and where hidden food might be tucked away. Over time, those clues accumulate into the deep, hard-earned knowledge that lets an orangutan survive alone.

A new study shows that this guide cannot form in isolation. It grows through shared experience, not through endless trial and error.

Humans also learn this way. We watch, copy, and build on the ideas of others. Researchers have wondered if wild apes follow a similar path. The new findings suggest that they do, and that their survival depends on it.

How orangutans build their diet

A young orangutan leaves its mother with knowledge of nearly 250 foods. It knows how to find them and how to handle them.

The recent study confirms that no individual could build such a broad list alone. Years of social contact shape this achievement. This long stretch of guidance forms what researchers call a culturally dependent repertoire.

Dr. Elliot Howard Spink, a postdoctoral researcher from the Max Planck Institute of Animal Behavior, is now a researcher at the University of Zürich.

“We provide convincing evidence that culture enables wild orangutans to construct repertoires of knowledge that are much broader than they could otherwise learn independently,” said Dr. Spink.

“These diets must be the product of experiences and innovations of many other individuals, which have accumulated over time,” noted Dr. Claudio Tennie from the University of Tübingen.

This idea aligns with long-standing theory. Learning with guidance shortens risky exploration. It pushes attention toward safe choices and speeds up the expansion of useful knowledge.

Why early diets matter

The forest gives young orangutans thousands of chances to explore, yet those chances mean little without social input. For many years, an immature ape stays close to its mother.

This closeness offers steady exposure to safe foods. It also provides access to rare opportunities, such as watching visiting adults feed or use objects.

These early years hold almost all the learning chances available across an ape’s life. After independence, social contact drops fast. That shift leaves little room for new lessons.

The study shows that young apes must reach adult-like diet breadth before this window closes. Otherwise survival becomes harder, especially during seasonal shortages.

A wide diet protects against scarcity. It lowers the risk of poisoning and provides the energy needed to build strength during late development. Narrow diets raise vulnerability at the exact moment independence begins.

A model to study wild orangutans

To test how learning actually unfolds, the scientists built an agent-based model calibrated with more than a decade of observations.

Each day in the simulation mirrors a day in the forest. The model presents feeding patches. It adds social states. It reflects the real frequency of food encounters recorded at Suaq Balimbing.

“Every single parameter of this model is based on our long term data from wild orangutans,” said study lead author Dr. Caroline Schuppli.

The model includes four social states – alone, distant association, close association and peering. Each state influences how likely a young ape is to explore.

Peering raises exploration sharply. Close association increases curiosity. Even distant association nudges attention toward feeding spots.

The model followed these states over 15 years of simulated growth, tracking how many foods a young ape learns. The team investigated whether independent exploration alone can match the pace seen in the wild.

The value of cultural learning

With full social input, simulated orangutans reach adult like diets at the same time as wild individuals. Learning rises quickly. Food repertoires match real patterns.

By the age of independence, most simulated orangutans know enough to support themselves.

When peering is removed, learning slows. Diet breadth shrinks. When both peering and close association vanish, progress drops sharply.

The model showed that exposure alone cannot build a complete diet, even when young apes encounter thousands of food patches over many years.

“Socially isolated, simulated orangutans still had hundreds of thousands of opportunities to encounter food items during development,” said Dr. Spink.

But even massive amounts of exposure to food could not replace what was lost when they couldn’t engage in these social interactions, he noted.

“We’re seeing the strongest evidence yet that orangutan diets are culturally accumulated over many generations,” said study co-author Andrew Whiten.

Orangutan diets across generations

The study also proposes that orangutan diets pass across generations. Mothers shape the earliest experiences. Other adults provide scattered but important lessons.

Males moving into new areas rely on peering to spot unfamiliar foods. This pattern suggests that knowledge in orangutan populations shifts through social contact, not strict instinct.

The research expands this idea further. Some differences between orangutan populations may reflect group level knowledge passed over decades. Subtle differences in food use may show cultural inheritance, much like regional habits among humans.

These insights reshape how scientists view ape learning. They also help explain why orangutans need long childhoods. A long childhood creates space to watch, practice, fail, and try again under safe supervision.

Significance of the research

The study carries practical weight. Many young apes in rehabilitation centers arrive without the cultural exposure needed for survival.

If released too early or without proper training, they face real danger. Some may starve. Some may eat toxic plants.

Rehabilitation programs now include forest schools that teach feeding skills. These programs guide young apes through safe exploration.

The new findings highlight why these steps matter. Without a wide diet repertoire, survival in the wild becomes uncertain.

“Reintroduction programs already teach orangutans to feed themselves outside captivity,” said Dr. Schuppli. “Our study emphasizes how important this is to pass on their full cultural menu, so that these animals have the greatest chance of success in the wild.”

The study is published in the journal Nature Human Behaviour.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–