Play is more frequent in captive adult chimpanzees than in captive adult lowland gorillas, according to a study published March 7, 2018 in the open-access journal PLOS ONE by Giada Cordoni and Elisabetta Palagi from Univerity of Pisa in collaboration with Ivan Norscia from University of Turin.
In many adult animals, play is thought to reflect a species' degree of social cohesion, and is usually more frequent in species with low levels of competition and high levels of social affiliation. Cordoni and colleagues compared adult play in chimpanzees and lowland gorillas, two ape species with different social structures. Chimpanzees live in highly cohesive, co-operative groups that can have several adult males.
However, lowland gorilla groups are dominated by a single silverback male and have low levels of social affiliation. The researchers observed 15 chimpanzees and 11 gorillas in the ZooParc de Beauval, France. Altogether, observations were made over more than 129 hours for chimpanzees and 135 hours for gorillas, with play including "peek a boo" and "tug-of-war" games as well as "rough and tumble" play fights.
The researchers found that adult play was more frequent in chimpanzees than in gorillas, and play sessions lasted longer. In addition, in gorillas play was more likely to escalate into real aggression. It appeared that the more players, the more unstable a play session and the more difficult to manage. While future work will show if affiliative relationships really determine differences in social play amongst great apes, the researchers' findings are in keeping with the differences in social structure of chimpanzees and lowland gorillas.