In a rare occurrence, researchers have recorded adult mountain gorillas playing on their own in water, just enjoying themselves.
Play is an important developmental process not just in humans but also in other primates.
Through play, humans and other animals gain more physical and mental acuity and learn behaviors that will serve them well into adulthood.
According to the World Wildlife Fund, "Gorillas share of their genetic code with humans, making them our closest cousins after chimpanzees and bonobos."
Like humans and many other primates, gorillas — especially throughout childhood and adolescence — engage in play, which allows them to learn key skills and behaviors. Play also allows young gorillas to strengthen their muscles and become more agile.
So far, researchers have focused mostly on studying play as a social activity, but they have paid less attention to gorillas' solitary play and what it might mean to them.
For this reason, a few recent sightings of mountain gorillas playing on their own in water have caught the attention of a team of investigators, from the Primate Research Institute at Kyoto University, in Japan, the Primate Cognition Research Group, in Lisbon, Portugal, and Conservation Through Public Health, a nonprofit organization in Entebbe, Uganda.
The sightings — which occurred at the Bwindi Impenetrable National Park, in Uganda — were even more unusual because the gorillas playing on their own were subadults and adults: a 9-year-old female, a 10-year-old female, a 7-year-old male, and a 15-year old male.
Gorillas just...want to have fun?
The scientists have published their findings in the journal . First author Raquel Costa and colleagues report that the sightings took place on three occasions at the end of the dry season in January 2018.
At these times, members of the Rushegura mountain gorilla group were seeking refreshment at a shallow stream.
During the first sighting, the 15-year-old male — called Kanywani — played on his own by submerging his fingers into the stream and making back-and-forth motions with his hand. "These movements were calm, and he did not splash the water," the researchers write in their paper.
On the same occasion, the 9-year-old female — whom the researchers call Kamara — played with the water in a similar way, also on her own.