Female orangutans are typically solitary creatures, but new research suggests they go out of their way—literally—to give their young a playmate. A study published by scientists at the Max Planck Institute of Animal Behavior in Konstanz, Germany, has found that mother orangutans travel further and eat less in the days before and after meeting up with other mothers who have offspring of a similar age, so the youngsters can play together.
The research, led by Odd Jacobson, examined 15 years of observational data on 31 wild Bornean orangutan mother-offspring pairs, totalling about 30,000 hours of field observations. The team found that mothers with similarly aged offspring spent a disproportionately high amount of time together in the same area. Youngsters tended to play in these situations, and play was more likely if the mothers were closely related. The findings are published in a peer-reviewed journal.
Play is essential for developing social and motor skills in many animals, yet orangutans are among the least social of the great apes. Mothers raise a single infant alone for six to seven years, so opportunities for social play are rare. “Our study provides strong evidence that wild Bornean orangutan mothers adjust their ranging behavior to increase their offspring’s access to social play,” the authors wrote.
The researchers ruled out the possibility that the meet-ups were simply coincidental gatherings near abundant fruit. The encounters occurred regardless of fruit availability, and the increased travel meant the mothers spent less time feeding. This suggests the playdates are deliberate and come at a cost to the mothers’ own foraging efficiency. “It’s possible that there’s something different about the way that mothers play with their babies and peers play, and they’re making a choice to get their babies socialised with peers,” said Zarin Machanda of Tufts University, who was not involved in the study.
Adriano Lameira, an orangutan expert at the University of Warwick, said the findings are consistent with what we know about orangutans’ cognitive abilities and their enormous parental investment. He does not believe the mothers call ahead—male orangutans use long calls to signal travel direction, but females are not thought to do so for social coordination. Instead, he suggests the meet-ups rely on local knowledge, such as which trees are fruiting or where good climbing structures are, combined with an ability to predict where other mothers will be. “One mother will likely be able to estimate, based on the other mother’s last location and typical range, which resources they will be searching for and where they will most likely be,” Lameira said.