Learning by watching: New insights into how nest-building skills are acquired and passed on.

By Dr Andrea L. Permana

Research Fellow, University of Warwick, UK and Max Planck Institute of Animal Behaviour.

When you think of wild orangutans, the chances are you picture one high in the trees moving through the rainforest canopy. But what you might not know is that every night, before they go to sleep wild orangutans must build themselves a brand-new bed in the trees. These beds are known as nests – and their construction is a task that they are not born knowing how to do but one which requires a surprising amount of knowledge and skill. But how do they learn how to build nests and how long does it take?

Our new study, published in Communications Biology, sheds light on this question. We collected data over 17 years on 44 wild Sumatran orangutans (Pongo abelii) at the Suaq Balimbing research site, in order to understand how young orangutans acquire their nest-building skills. The answer lies in something deeply familiar to us: watching others and practice!

Image of an orangutan nest

 Learning by watching

Young orangutans do not instinctively know how to build nests. Instead, they gradually master the skills over more than 7 years, which we demonstrated in a previous paper published in the Animal Behaviour in 2024. To investigate how nesting skills are acquired, we focussed on a behaviour called ‘nest peering’ – when an individual closely watches another individual building a nest.

Our findings show that nest peering plays a critical role in nesting skill acquisition. Immature orangutans who spent more time peering were significantly more likely to engage in nest practice themselves. Interestingly, just being close to another individual building a nest was not enough. What also mattered was focused attention. Nest peering was most often directed at the more complicated parts of nest-construction – such as night nests, tying trees together to make multi-tree nests, or making a pillow, blanket or roof – the kind of features which require several steps to complete and therefore more careful learning.

Watch a video taken in 2024 of oragutans building their nests

Know-how and know-what

Our study also found that orangutans don’t just learn how to build a nest, they also learn what to build them with. Young orangutans tend to use the same species of tree as the individual they have been peering at. For dependent youngsters, this is usually the mother. But as they grow independent, they begin to peer at a wider range of individuals and adjust their nest-building materials accordingly, becoming more explorative and likely acquiring some different ways of doing things. This dual transmission of know-how (the techniques) and know-what (the materials) is a clear example of observational social learning. Which has previously proven extremely difficult to show in wild animals. Indeed, it is a sophisticated way of acquiring survival skills and suggests that orangutans, like humans, use selective focussed attention to pick up both actions and contextual knowledge.

Why does it matter?

Understanding how orangutan learn is not purely an academic question. It offers valuable insights into the evolution of learning and culture in primates – including our own species. It also underlines the importance of social environments for cognitive development. Our research is part of a growing body of evidence showing that orangutans have complex learning processes. They watch, select and practice – and over many years, they master this and other key skills that are an essential part of life in the tree-tops.