Mothers of the most solitary great ape plan and structure playdates, even when it comes at a cost

October 07, 2026

Orangutan mothers seek out playmates for young | Max-Planck-Gesellschaft

Behavioral Biology Biodiversity

To the Point

• Investing in play: orangutan mothers adjust ranging behavior to increase their offspring’s access to play with neighboring peers.
• A new form of investment: mothers actively provide young with social contact, even at a cost to their own energy budget.
• Hidden cost of solitary living: social play seems to be a requirement across all great apes, and some solitary species must accept a cost to meet that need.

Playing with peers is a crucial part of growing up; so crucial, that orangutan mothers will go out of their way to arrange playdates for their young, according to a 15-year study on wild Bornean orangutans.

Orangutans are the most solitary of all great apes. Mothers spend most of their time alone with their youngest offspring, who remain dependent for their first seven or more years of life. Infants have little opportunity to meet youngsters their own age, yet playing together helps to build the strength and social skills that they need later in life.

Now scientists have strong evidence that orangutan mothers look for opportunities for their young to play with similarly aged playmates, even travelling further to do so.

“We reveal a hidden cost of solitary living,” says Maria van Noordwijk, senior author of the study. “On top of providing food and safety for their young, orangutan mothers are tasked with supplying social resources too.”

The study was led by scientists from the Max Planck Institute of Animal Behavior together with the University of Zurich, Universitas Nasional, and Rutgers University.

Orangutan play

Orangutan kids have a ‘play button’ that only mom can switch off. Here’s how Maria van Noordwijk and Odd Jacobson studied this behavior

A longstanding mystery

Since 2003, van Noordwijk and her team have followed mother-infant pairs at Tuanan Research Station on the island of Borneo in Indonesia, where they observed habituated orangutans from morning to night. Encounters between mothers are rare, but when they do happen, they’re a cautious affair.

“Adults usually don’t get very close to each other,” says van Noordwijk, a fellow at the Max Planck Institute of Animal Behavior, who led the fieldwork while at University of Zurich. Infants, though, are a different matter. “They zoom towards each other, roughhousing, biting, grappling,” she says. “Orangutan kids have a ‘play button’ that only mom can switch off when she decides it’s time to move on.”

Van Noordwijk noticed that these infant encounters seemed to come at a cost to the mothers. “It just looked like a really long, hard day for them,” she says. “I knew there was something going on with these playdays, but we needed the right statistical technique to verify this.”

Playdates with peers

After 15 years, van Noordwijk’s team had amassed 32,000 hours of observations from 31 mother-infant pairs. Working with Odd Jacobson, a postdoctoral researcher at the Max Planck Institute of Animal Behavior, she tested whether mothers were actively seeking out playmates for their young. “We applied a statistical technique that combined mothers’ space use with social characteristics of neighboring mother-infant pairs,” says Jacobson, the paper’s first author.

Jacobson found that mothers with infants closer in age shared more of the same forest areas, and those infants also played together more often, even after accounting for factors such as relatedness and fruit availability.  “Mothers appear to match their kids with play partners that are physically and developmentally suitable,” says Jacobson.

Playdates also carried a clear movement signature. Mothers travelled further not only on play days themselves, but also on the days surrounding play. Adult females are known to have a core area, where they spend most of their time. Starting on the day before play, mothers moved toward the other mother’s core area; and after play, they moved back toward their own core area. These patterns suggest that orangutan playdates are not chance meetings, but are actively shaped by mothers’ ranging decisions.

Mapping the social landscape

“To find a suitable playmate it seems that they position themselves spatially to increase the likelihood of encountering mothers with similarly-aged offspring,” says Jacobson. This targeted movement illustrates that mothers are aware of what van Noordwijk calls the “forest gossip.”

“Orangutans might spend most of their day alone, but they are still embedded in a social network. They know exactly who their mostly life-long neighbors are, and they know who had a baby when. From their treetop positions they can probably get a rough sense of where these neighbors are, at least on occasion.”

The ability to navigate this social landscape may draw on known cognitive skills of orangutans. “We have accepted for a long time that they apply spatial navigation and route planning to locate and access food resources,” says van Noordwijk. “Now we show that they are combining a cognitive map of not only feeding but also social resources in order to provide for their young.”

Mothers pay the price

All this effort comes at a cost. Mothers spent more time travelling and less time feeding on days associated with playdates, representing an overlooked form of maternal investment in their offspring’s social development.

“In many social species, playmates come naturally with group living,” says Jacobson. “The play problem arises when moms spend most of their time alone with a single young and don’t regularly come together for feeding, socializing, or protection.” How many other species face this same problem, and how they solve it, remains unknown.

The authors acknowledge that playdates are rare, occurring on just six percent of the days that a mother-infant pair was followed, or roughly once every 20 days. And on days when infant peer play did occur, they spent only around 20 minutes doing so in total.

Whether that investment ultimately pays off remains an open question. “We still don’t know if the time and energy mothers spend arranging playdates give their young an advantage later in life,” says Sri Suci Utami Atmoko, coauthor from Universitas Nasional, Indonesia. “What is certain is that only long-term studies like these can possibly unlock the answer. Discoveries like this depend on sustained research, allowing us to connect behavior with development, environment, and demography across the lifespan of these long-lived species.”

The findings also raise a broader question: what do we gain from living socially, and what do we pay when social contact is scarce? Meg Crofoot, a coauthor and director at MPI-AB says: “In some ways, we are more like orangutans than we realize. We evolved to raise children in large groups, but modern life is increasingly pushing us into a solitary lifestyle. Orangutans remind us of what we lose when we isolate ourselves. When opportunities for social contact are limited, someone has to pay the cost.”

ByAvery Porter Published: Oct 08 2026, 9:40 PM EDT

Three Dead Alaska Polar Bears Were Infected with H5N1 Bird Flu, Study Finds, but Signs of Immunity Are Emerging

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A new study has found that three polar bears found dead in Alaska in 2023 and 2024 were infected with highly pathogenic H5 avian influenza, the same clade 2.3.4.4b viruses that have spread through wild birds, poultry, and mammals across North America. The research, reported by the University of Minnesota’s CIDRAP in late September, adds to evidence that the virus is reaching top Arctic predators.

The study’s authors offered a notable caveat. “These data indicate that HPAIV infection may represent an emerging threat to polar bear health within the Alaska Arctic; though population immunity seems to be building and may protect this species from widespread demographic impacts of disease,” they wrote.

The findings arrive at a seasonal turning point. Fall bird migration typically brings a rise in avian flu detections, and Minnesota has again become a national hot spot for both poultry and wild-bird cases. For most Americans, the immediate practical risk is low, but the wildlife findings show how far the virus has traveled.

A Virus Reaching the Top of the Arctic Food Chain

Polar bears are listed as threatened under the Endangered Species Act and normally hunt seals on sea ice. The first known polar bear death from H5N1 anywhere was a young male found near Point Barrow, Alaska, in 2023. A case report in the CDC’s journal Emerging Infectious Diseases found brain inflammation as the main sign of disease and noted that seabirds called short-tailed shearwaters had tested positive for the virus near the same spot that summer.

Researchers believe bears likely become infected by scavenging infected bird carcasses or other dead animals. Alaska state veterinarian Bob Gerlach has said that when an infected bird dies in a cold environment, the virus can be maintained for a while — a risk for any predator that scavenges. Seabird colonies hit by outbreaks can leave many dead birds in one place.

The new study expands that picture to three infected bears across two years. Carcasses in the far north are often found only by chance, by local residents or wildlife monitoring programs such as those run by the North Slope Borough, and Gerlach has said more bears may have died unnoticed in remote areas. It does not mean the virus is spreading widely from bear to bear, and the authors did not report evidence of large-scale die-offs.

Signs That Immunity May Be Building

The most important nuance is the evidence of exposure without death. When animals survive infection, they develop antibodies that show up in blood tests. A U.S. Geological Survey data release published in May 2026 documented blood samples from Alaska polar bears tested for prior exposure to these viruses.

A separate study from Norway points the same way. Researchers reported H5N5 bird flu in a dead yearling polar bear and a walrus in Svalbard in May 2026. In blood samples, H5 antibodies appeared in 75% of polar bears tested in 2023 and 97% in 2024 and 2025, compared with none from 2014 to 2022. That work was posted as a preprint and has not yet been peer reviewed.

Together, the findings suggest many bears have been exposed and survived — a very different picture from a species-wide die-off. That would be encouraging for a species already under pressure from shrinking sea ice. Still, researchers cannot yet say how long protection lasts, whether it protects against newer virus strains, or how many deaths go unnoticed in remote areas where carcasses are quickly scavenged.

Fall Outbreaks in Minnesota and Beyond

Closer to most readers, avian flu activity is picking up with fall migration. In the 30 days before CIDRAP’s late-September report, the U.S. Department of Agriculture confirmed H5N1 in 20 flocks, including 13 commercial farms and seven backyard flocks, affecting about 560,000 birds.

Minnesota accounted for six of eight new poultry outbreaks in that week’s update, including two commercial turkey facilities in Stearns County. The largest single outbreak was at a commercial turkey operation in Barron County, Wisconsin, with 79,100 birds affected. Minnesota also reported at least 40 wild-bird detections over 10 days, most in the seven-county Minneapolis-St. Paul area, including mallards, Canada geese and three bald eagles.

Poultry outbreaks can affect egg and turkey supplies regionally, especially heading into the holiday season, though one week of detections does not predict prices.

Human Risk and Practical Precautions

The Centers for Disease Control and Prevention says that “while the current public health risk is low,” it is monitoring the situation and working with states to track people exposed to infected animals. CDC’s current situation summary lists 71 reported human cases in the United States since February 2024, most among people with direct exposure to infected poultry or dairy cattle.

No person-to-person spread has been documented. People face the greatest risk when they handle sick or dead birds or animals without protection, which is why poultry workers, backyard flock owners, and hunters are urged to take care.

Practical steps are simple. Do not touch sick or dead wild birds or mammals with bare hands. Hunters cleaning waterfowl this fall should wear gloves, work outdoors or in well-ventilated areas, and wash up afterward. Backyard flock owners should keep their birds away from wild waterfowl and report sudden deaths to their state veterinarian. Keep pets away from dead birds. Report unusual wildlife die-offs to your state wildlife agency.

There is no need to avoid properly cooked poultry or eggs, and residents do not need to change daily routines based on the polar bear findings.

The bottom line: H5 bird flu has now been confirmed in three dead Alaska polar bears, but rising antibody levels suggest many bears are surviving exposure. Fall migration is driving new outbreaks in poultry, while CDC still rates the risk to the public as low. Monthly USDA and CDC updates will show whether this fall’s wave grows.

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