Young orang-utans acquire their knowledge of food and foraging skills through both social and individual learning. A greater tendency towards both learning processes results in the most varied diet by the time the animal is old enough to fend for itself.
Young Sumatran orang-utans (Pongo abelii) develop their repertoire of foraging skills by both observing their mother’s behaviour and exploring objects on their own, an international research team reports on 24 September in Science. Individuals with a stronger tendency towards both social and individual learning have the most varied diet by the time they reach independence; both forms of learning thus contribute to the animals’ ecological competence.
250 food sources
Orang-utans remain with their mother for the first eight years of their lives. After this developmental period, they must be able to survive independently in the wild. The diet of adult Sumatran orang-utans encompasses a challenging total of around 250 different food sources. It is therefore crucial that young great apes learn what is edible, when and where these food sources can be found, and how to process food before eating it. Individual learning is generally assumed to be less efficient and to carry greater risks, such as poisoning and predation. Social learning, by contrast, increases the reliability of information and provides a more complete and up-to-date picture. To investigate whether and how both forms of learning interact during development, the authors analysed wild Sumatran orang-utans over the eight-year dependency period.
Moments of observation
Over more than 1,700 hours of direct observation of 21 immature individuals, spanning more than a decade of research, the researchers recorded more than twice as many instances of young great apes exploring on their own as instances of them closely watching their mother. However, the research team found that most cases in which immature orang-utans independently handled objects were not independent of prior observation of their mother. This points, in their view, to a previously underappreciated, close intertwining of social and individual learning. The authors therefore classify instances of exploration that occurred within 145 minutes of an informative interaction with the mother as ‘socially initiated’. By this reasoning, social learning occurs five times more frequently than individual learning.
The researchers also report that not every young orang-utan shows the same tendency to learn. Individuals with the strongest tendency towards both social and individual learning eat the greatest number of different food sources at the point of independence. Social learning appears to have a compensatory effect on dietary development when individual learning is limited. Further research is needed to understand what drives this pattern and the extent to which the relative contribution of both learning processes depends on local conditions.