New research from the University of St Andrews has found that the amount of knowledge a wild orangutan acquires over its long juvenile development depends on its style of learning, both socially and individually.
In a paper published today (24 September) in Science, Researchers studying wild orangutans in Sumatra have been able to assess for the first time the scale of learning by juveniles' before they achieve independence from their mothers.
Infant orangutans differ greatly from one another in how frequently they engage in social versus individual learning.
Orangutans hold the record for diligent maternal care, which lasts as long as eight or more years before youngsters can be weaned and forage independently. For orangutans this requires learning the approximately 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 these years is substantially greater than has yet been appreciated for any non-human animal.
Researchers from St Andrews, in collaboration with the Max Planck Institute of Animal Behavior (MPI-AB) in Germany, used long-term data from the Suaq Balimbing monitoring station in Indonesia, and analysed 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 behaviours were recorded as indicators of social learning, and instances in which juveniles explored the world themselves were recorded as indicators of individually driven learning.
Examining how long it took after an episode of attentive peering for juveniles' own explorations to deviate from the effects of this social information, the surprising answer was that on average it was as long as two and a half hours. This translates into youngsters acquiring 5-6 times more knowledge from their mother and others than their own purely independent explorations.
This is the first study of cultural inheritance in a wild animal to assess the totality of social and individual learning that goes into achieving the repertoire of behaviour needed for independent adult life. The team found that social and individual learning worked powerfully in tandem to achieve this, 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.
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.
Co- author Professor Andrew Whiten from the School of Psychology and Neuroscience at St Andrews, said: "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."
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.
