Differences in play can illuminate differences in affiliation: A comparative study on chimpanzees and gorillas.

Giada Cordoni,Maria Bobbio,Elisabetta Palagi,Ivan Norscia,Kim A Bard

doi:10.1371/journal.pone.0193096

Giada Cordoni, Maria Bobbio + Show 3 more

Open Access

https://doi.org/10.1371/journal.pone.0193096

Copy DOI

Journal: PloS one	Publication Date: Mar 7, 2018
Citations: 23	License type: CC BY 4.0

Affiliation: University of Pisa, University of Turin

Abstract

Play behaviour reinforces social affiliation in several primate species, including humans. Via a comparative approach, we tested the hypothesis that play dynamics in a group of lowland gorillas (Gorilla gorilla gorilla) are different from those in a group of chimpanzees (Pan troglodytes) as a reflection of their difference in social affiliation and agonistic support. We selected one group of lowland gorillas and one of chimpanzees, hosted at the ZooParc de Beauval (France), managed in a similar way and living in similar enclosures. The same observers video-collected and analysed data on play behaviour in both groups, by applying identical methodological procedures. Data showed that adult play was less frequent in the group of gorillas compare to chimpanzees. Polyadic play, which involves more than two players and is characterised by the most uncertain outcome, was also less frequent in gorillas than chimpanzees. Play sessions were more unbalanced (more unidirectional patterns by one of the player towards the other) in chimpanzees than in gorillas but in the latter play escalated more frequently into serious aggression. Play asymmetry in the gorilla group increased as the number of players increased, which explains why gorillas limited their polyadic playful interactions. In conclusion, our findings on the study groups of apes can be a valuable starting point to expand the study of social play in the great apes to evaluate if inter-individual affiliative relationships really account for the differences in play distribution and dynamics.

Highlights

Compared to ‘serious’ behaviors, whose functions are immediately evident, play is a difficult behavior to contextualize from both a functional and an operational point of view
Before testing the predictions relative to play dynamics in the two species, we explored if our study groups reflected the social characteristics already reported in literature for chimpanzees and gorillas
The values of Agonistic Support Index were significantly higher in chimpanzees than in gorillas (Mann-Whitney exact test: U = 27.50, NG = 10, NC = 13, P = 0.014; Fig 1a; S2 Table)

Summary

Introduction

Compared to ‘serious’ behaviors, whose functions are immediately evident (e.g., sexual behavior, aggressive behavior), play is a difficult behavior to contextualize from both a functional and an operational point of view (for an extensive definition of play see [1]). When we talk about play we immediately think about its long-term benefits, such as motor, cognitive and social skill improvement [2,3]. It has been demonstrated that play can reduce social anxiety linked to particular contexts such as crowded condition (gorillas, [4]; bonobos, [5]), pre-feeding. Play dynamics in chimpanzees and gorillas competition (chimpanzees, [6]; bonobos, [7]; common marmosets, [8]; wolves, [9]), intra-sexual (sifaka, [10]) and inter-sexual competition (brown bears, [11]). Recent findings on the distribution of play as a function of sex, age, relationship quality, and distribution of power, suggest that play can be shaped according to the social structure and the inter-individual relationships that characterize each group [21]

Methods

Results

Conclusion