Orangutan mothers – Over 15 years of observations of wild Bornean orangutans suggest mothers sometimes travel into neighboring territories to line up play for infants with similarly aged offspring—so much so that the extra distance comes with reduced feeding time.
For days, the direction of travel changes. Then the youngsters are suddenly close to each other.
A new analysis of wild Bornean orangutans points to a striking possibility: mothers may make trips into the territories of other mothers with similarly aged infants so the young can play together. The picture matters because play is how many animals learn—building social and motor skills and shaping behavior that lasts. Orangutans, though, are widely described as solitary. Mothers typically raise a single infant for six to seven years. and young orangutans only socialize when they happen to meet. How those meetings occur, and whether they’re simply luck, has been hard to pin down.
Zarin Machanda at Tufts University in Massachusetts starts from a different angle. She says the assumption might be that orangutans need less play because they’re less social than other apes—yet orangutan males still have to fight. so they would need somewhere to practise. That question shaped the hunt for answers.
Odd Jacobson at the Max Planck Institute of Animal Behavior in Konstanz. Germany. and his colleagues worked through 15 years’ worth of data on 31 wild Bornean orangutan (Pongo pygmaeus wurmbii) mother-offspring pairs. The dataset totals about 30. 000 hours of observations recording where the animals were. whom they were with. and what they were doing.
What they found is difficult to ignore: mothers with similarly aged offspring spent a disproportionately high amount of time together in the same area. When that happened, the youngsters tended to play. Play was also more likely if the mothers were closely related.
And the mothers’ movement didn’t look random. The distance the apes travelled increased in the days before and after the so-called playdate, as mothers headed into a neighbor’s territory and then returned home.
In Jacobson and colleagues’ write-up, the conclusion is blunt: the study provides strong evidence that wild Bornean orangutan mothers adjust their ranging behavior to increase their offspring’s access to social play.
But playdates that look intentional could still be something else. The researchers note a possible alternative explanation: the young might simply be playing where orangutans congregate because fruit is plentiful—an idea compared to brown bear cubs playing together when their mothers converge on a river full of salmon. Yet the meet-ups happened regardless of how much fruit was available in the area.
Even more telling, the extra travel meant less time feeding. That trade-off led the team to suggest the encounters are planned at a cost to the mothers’ own foraging, rather than being part of it.
Machanda cautions that intentionality is almost impossible to determine from behavioural data alone. Still. she adds that it’s possible “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.”.
Adriano Lameira at the University of Warwick in the UK sees the results fitting with the long-term investment orangutans make in raising offspring. and with their cognitive abilities. He doesn’t think the mothers are calling ahead to arrange meetings, though. Male orangutans use long calls to communicate their travel direction a day in advance. he says. but females aren’t thought to use long-distance calls for social coordination.
For Lameira. the likely mechanism is local: what the mothers can hear and see from the trees. their local knowledge—such as which trees are fruiting or where there are big lianas for youngsters to climb—and the ability to anticipate what another mother might do. “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 says.
Taken together. the findings sharpen a question that has sat in the background of orangutan social life: if play is vital. how do solitary adults find ways to deliver it?. The data can’t prove mothers are planning playdates in a human sense—but the patterns in timing. territory crossing. relatedness. and the feeding trade-off make one thing harder to dismiss: the youngsters aren’t just stumbling into each other by chance.
orangutans Bornean orangutan play behavior mother-offspring animal behavior Max Planck Institute Zarin Machanda Odd Jacobson ranging behavior cognition