Gesture Use in Communication between Mothers and Offspring in Wild Orang-Utans (Pongo pygmaeus wurmbii) from the Sabangau Peat-Swamp Forest, Borneo

Andrea Knox,Frank J F Van Veen,Helen Morrogh-Bernard,Abdul Azis,Joey Markx,Emma How,Catherine Hobaiter

doi:10.1007/s10764-019-00095-w

Abstract

Research on captive and wild great apes has established that they employ large repertoires of intentional gestural signals to achieve desired goals. However, gestural research has focused on African great apes, with orang-utan data limited to a few captive studies. We address this gap by describing gesture use in wild Southwest Bornean orang-utan (Pongo pygmaeus wurmbii) mother and offspring pairs. We conducted focal follows on 16 individuals in the Sabangau peat-swamp forest in Borneo, Indonesia. The resulting 681 h of video footage yielded 1299 communicative signals: 858 vocal signals and 441 gestural signals. Eleven vocal signal types and 21 gesture types met the criteria for inclusion in the repertoire; however, the gestural repertoire did not approach asymptote and further gesture types will likely be identified in the future. Signalers used gestures of any modality in higher frequency when the recipient was paying visual attention, and took the recipient’s visual attention into account when selecting gesture modalities. Orang-utans employed hands and arms more than legs and feet in gesturing, but were more flexible in their choice of limb than chimpanzees using the same gestures. Orang-utans were highly responsive to gestural requests, using them to achieve eight goals and, where successful, responding either before gesturing ended or in <1 s in 90% of communications. Our findings on the range of gesture types and impact of visual attention support findings from captive orang-utans; and those on responsiveness and limb use highlight the importance of studying ape communication in the social and ecological context to which it is adapted.

Highlights

Nonhuman great apes’ use of 60–80 gestures in intentional communication remains the only broad system of communication outside of human language in which there is evidence for widespread and flexible use of goal-directed signals to communicate language-like meaning in everyday social interaction (Graham et al 2018; Hobaiter and Byrne 2014, 2017; Moore 2014)
We further explore the responsiveness of orang-utans to gestural communications and describe the range of goals for which gestures are employed between mother– offspring pairs
In addition to the 21 gestures included in the repertoire, an additional five gesture types were observed on a single occasion

Summary

Introduction

Nonhuman great apes’ (hereafter great apes) use of 60–80 gestures in intentional communication remains the only broad system of communication outside of human language in which there is evidence for widespread and flexible use of goal-directed signals to communicate language-like meaning in everyday social interaction (Graham et al 2018; Hobaiter and Byrne 2014, 2017; Moore 2014). Researchers have started to describe the way in which apes combine their signals; with gestures, vocalizations, and facial expressions, among other signals, employed in a single communicative system. These studies have highlighted the importance of considering communication holistically (Hobaiter et al 2017; Liebal et al 2011; Wilke et al 2017), as well as blurring the boundary between signal categories (e.g., orang-utans’ use of their hands to modify the acoustic properties of some vocalizations: Lameira et al 2013; Peters 2001). Gestural research efforts have focused mostly on the African great apes, with detailed repertoires described for the gesturing of both captive and wild chimpanzees (e.g., Bard et al 2014; Hobaiter and Byrne 2011a; Pollick and de Waal 2007; Roberts et al 2012; Tomasello et al 1985, 1989), bonobos (e.g., Genty et al 2014, 2015; Graham et al 2017; Halina et al 2013; Pika et al 2005), and gorillas (Byrne and Tanner 2006; Genty et al 2009; Pika et al 2003; Tanner et al 2006), while gestural research on orang-utans is limited to a few captive studies (Cartmill 2008; Cartmill and Byrne 2007, 2010; Liebal et al 2006; cf. Mackinnon 1974 for descriptions of wild orang-utan signals, Bard 1992 for gesture use in free-ranging reintroduced individuals, and Waller et al 2015 for facial displays)

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Conclusion