Immature wild orangutans acquire relevant ecological knowledge through sex-specific attentional biases during social learning

Abstract

As a part of growing up, immature orangutans must acquire vast repertoires of skills and knowledge, a process that takes several years of observational social learning and subsequent practice. Adult female and male orangutans show behavioral differences including sex-specific foraging patterns and male-biased dispersal. We investigated how these differing life trajectories affect social interest and emerging ecological knowledge in immatures. We analyzed 15 years of detailed observational data on social learning, associations, and diet repertoires of 50 immatures (16 females and 34 males), from 2 orangutan populations. Specific to the feeding context, we found sex differences in the development of social interest: Throughout the dependency period, immature females direct most of their social attention at their mothers, whereas immature males show an increasing attentional preference for individuals other than their mothers. When attending to non-mother individuals, males show a significant bias toward immigrant individuals and a trend for a bias toward adult males. In contrast, females preferentially attend to neighboring residents. Accordingly, by the end of the dependency period, immature females show a larger dietary overlap with their mothers than do immature males. These results suggest that immature orangutans show attentional biases through which they learn from individuals with the most relevant ecological knowledge. Diversifying their skills and knowledge likely helps males when they move to a new area. In sum, our findings underline the importance of fine-grained social inputs for the acquisition of ecological knowledge and skills in orangutans and likely in other apes as well.

Sociality predicts orangutan vocal phenotype

“…Our findings show that the degree of sociality experienced by individual orangutans in the wild moulds their vocal personality. Findings converge with evidence for active social learning in wild orangutans 109 , 110 , 114 that suggest that socially sourced information crosses over into the vocal and communicative domain. We confirm that like human learners exposed to different linguistic communities, social settings help modulate vocal output dynamics and structure in nonhuman hominids.…”

“…First, number of tutors probably affects vocal dynamics of novices. For example, marmoset infants attend to one or two tutors during development, but young orangutans seek interaction with multiple adult conspecifics as they gradually become independent 85 , 106 – 110 , becoming exposed to larger pools of ‘role models’ for the acquisition of new behaviours and skills across domains 73 , 74 . Indeed, when songbirds were experimentally presented with an increased abundance of role models, similar results were obtained 4 .…”

Molecular assessment of dietary variation in neighbouring primate groups

“…Albeit, sex was not a significant predictor for the present data, it could be worthwhile to study possibly greater behavioural flexibility of the dispersing group members, adult males, as shown previously in behavioural experiments and discussed above (Bono et al, 2018; van de Waal et al, 2013). Furthermore, it has been found that the sex of an individual can already lead to dietary variations in juveniles as described for orangutans (Ehmann et al, 2021). Here, this effect was not significant but the structure within the NMDS still suggests differences between male and female juveniles (Figure S7).…”

The role of great ape behavioral ecology in One Health: Implications for captive welfare and re‐habilitation success

“…These two very different experiences of human contact may elicit mixed responses towards humans in these apes. Moreover, as a consequence of their capture, they have often missed out on infancy and early juvenility with their mothers and/or natural groups and have thus lost a key window of opportunity for learning the natural behavioral profiles of their species van Noordwijk & van Schaik, 2005) or sex (Ehmann et al, 2021). While all species of great apes face similar challenges, we focus on the example of orangutans (Pongo abelii, Pongo pygmaeus, and Pongo tapanuliensis) since they experience a variety of captive care settings, and because they are currently the only great ape taxon for which there are active and systematic programs of re-introduction into natural habitat which follows IUCN best practice guidelines (Beck et al, 2007).…”

“…These two very different experiences of human contact may elicit mixed responses towards humans in these apes. Moreover, as a consequence of their capture, they have often missed out on infancy and early juvenility with their mothers and/or natural groups and have thus lost a key window of opportunity for learning the natural behavioral profiles of their species (Schuppli, Forss et al, 2016; van Noordwijk & van Schaik, 2005) or sex (Ehmann et al, 2021).…”