Learning from their moms key to survival for young orangutans

By Stephen Beech

Learning from mother is key to adult survival for young orangutans, reveals new research.

Scottish scientists found that the amount of knowledge a wild orangutan acquires over its lengthy juvenile development depends on its style of learning.

Researchers studying wild orangutans in Sumatra discovered that over their development of up to 8.5 years, infants differ from one another in how frequently they engage in social and individual learning.

The team's findings, published in the journal Science, assessed for the first time the scale of learning by juvenile orangutans before they achieve independence from their mothers.

The great apes hold the record for diligent maternal care, which can last eight or more years before youngsters can be weaned and forage independently.

For orangutans that requires learning around 250 dietary items that need to be extracted from the rainforest, some requiring the use of simple tools.

The new study shows that the scope of the cultural heritage that passes from their doting mother to the infant over those years is "substantially greater" than has yet been appreciated for any nonhuman animal.

Researchers from St. Andrews, working with scientists from the Max Planck Institute of Animal Behavior (MPI-AB) in Germany, looked at long-term data from the Suaq Balimbing monitoring station in Indonesia.

Revathe Thillaikumar, a postdoctoral fellow at MPI-AB, said: "Until now, whether and how wild animals use different forms of learning to develop their survival-relevant skills have remained unknown."

The team analyzed nearly 7,000 records of youngsters' experiences obtained during 4,700 hours of dawn-to-dusk observations spanning 12 years of field study.

Instances of young orangutans closely peering at details of their mother's habits were recorded as indicators of social learning, and instances in which juveniles explored the world themselves were recorded as indicators of individually driven learning.

The researchers found that examining how long it took after an episode of attentive peering for juveniles' own explorations to deviate from the effects of that social information, the surprising answer was that on average it was as long as 2.5 hours.

They say that translates into youngsters acquiring five to six times more knowledge from their mother and others than their own purely independent explorations.

The team found that social and individual learning worked powerfully in tandem, with juveniles showing the highest rates of both forms of learning achieving independence with the most comprehensive dietary profiles, in preparation for their adult lives.

But when both forms of learning were low, individuals ended up with the lowest diet breadth, with a threefold difference between high and low learning of both forms.

Study senior author Caroline Schuppli, of MPI-AB, said: "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."

The team analyzed data from 21 immature orangutans recorded from birth to independence at around 8.5 years of age.

Thillaikumar said: "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.

"We were astonished by how different infants were from one another in their tendencies to learn."

Schuppli said: "Learning purely through individual exploration can be risky for a naive 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."

The team found that when infants engaged in social learning, it triggered subsequent exploration for as long as 2.5 hours.

Thillaikumar said: "Each time an infant peered, it had a prolonged, ripple effect on subsequent explorations."

The finding suggest that increased social learning could even partially compensate for low individual learning by improving diet breadth.

Thillaikumar said: "Social learning stepped in to do the heavy lifting, which shows us just how significant it is in the lives of great apes."

Schuppli said: "It's about more than just social or individual learning.

"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."

The results show that heightened learning results in broader diets.

Sri Suci Utami-Atmoko, of Universitas Nasional in Indonesia, said: "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."

Study co-author Andrew Whiten, from St. Andrews' School of Psychology and Neuroscience, added: "These findings about the extent of cultural and individual learning during these apes' long childhoods suggest that this pattern, that we clearly share with them, has origins all the way back to our common ancestors, many millions of years ago."