Captive Adult Chimps And Playtime: Does It Mean They’re Happy?
Social relationships can be a source of both stress and well-being in humans and chimpanzees alike. For chimpanzees in captivity, the ability to get along and live in groups with as little stress as possible is especially important. Researchers have focused a lot on certain types of social interaction, such as social grooming, which helps chimpanzees stay clean and form social bonds. But, they have not focused much on the significance of social play, especially between adult chimpanzees. This is partly because social play between adults is relatively uncommon in chimpanzees. Nevertheless, it is important to determine what we can understand about the welfare of adult captive chimpanzees from studying their social play.
This study, published in the journal of Applied Animal Behavior Science, looked at social play among 37 adult chimpanzees. They were between the ages of 9 and 44. And they lived in Kumamoto Sanctuary in Japan. After analyzing a total of 367 hours of behavioral observations on mixed-sex and all-male groups, the researchers noted several interesting findings.
One pattern that researchers noticed was that social play between females occurred much less often than social play between males or between different genders of chimpanzees. When comparing all-male groups with mixed-sex groups, researchers noticed a higher rate of both playful and aggressive interactions in all-male groups. Another finding of this study was that rates of both social play and unreciprocated social grooming peaked at mid-day and before feeding time (which is a relatively tense time of day for these chimpanzees). These peaks were not found in this pattern for reciprocated social grooming. Researchers noted a spike in aggressive interactions during pre-feeding times. But, the main peak for aggressive interactions occurred earlier in the day (12:00–12:30pm).
The researchers additionally wanted to determine the relationships among social grooming, social play, and aggressive interactions. They found that, while mutual social grooming was negatively correlated with aggressive interactions, social play was not significantly correlated with aggressive interactions. Yet, social play and mutual social grooming were negatively correlated. Based on these findings, the researchers concluded that mutual social grooming was a sign that two chimpanzees got along. This is because chimpanzees who groomed each other were less likely to engage in aggressive behavior toward each other.
The situation was sometimes different for individuals who engaged in social play together. Chimpanzees who engaged in social play together were no less likely to behave aggressively toward one another. The researchers theorize that social play may be a way for chimpanzees to reduce tension and tolerate others whom they may not have particularly strong bonds with. Interestingly, researchers also found that within all-male groups, rates of adult social play increased with age. The researchers speculate that perhaps older chimpanzees know the value of social play in reducing social tensions, meaning they may use it as a tool to do so. But, more research is necessary before making any definitive conclusions.
The findings of this study do not support using adult social play as an absolute positive indicator of welfare. Social play may just be a way for chimpanzees to handle the tensions of group living. The researchers suggest that future studies “investigate social play and its relevance to the internal states in more diverse types of social groups and in more diverse social situations in depth.” The findings of this study are a useful reference for developing welfare assessments for adult chimpanzees.