(The Center Square) – It turns out that, regardless of whether or not chimpanzees have a lot of food available, or little food around, mothers will still play with their children. Moreover, when other youths play too rough, young chimps go back to their mom.

Adult chimpanzees play together less under these conditions, but things like tickling and chasing continue with mother chimps and their offspring, according to a new study, the University of New Mexico said.

The study, titled Ecological “variation in adult social play reveals a hidden cost of motherhood for wild chimpanzees”, was published in Current Biology.

Here are the highlights of the research, according to the release.

Adult chimpanzees played more often with all partners when diet quality was highUnlike other dyads, only mother-offspring play persisted when diet quality was lowPlaying with offspring helps balance the costs of grouping with offspring needsLike with humans, parent-offspring play may be crucial to development for chimpanzees

The researchers expected seasonal variations in the level of play with mother chimps and their offspring. However, that wasn’t the case.

“For example, when supplies of quality fruits were low, the chimps focused on finding and gathering figs and leaves and put play time aside,” the release said. “Surprisingly, although chimp mothers had the same challenge in finding food, they continued devoting a lot of their time to nurturing their offspring’s development through play.”

Chimpanzee social structure may be a possible reason for this, however. When food is plentiful, chimps congregate in larger groups, which often include as many as 60 chimps. However, when food is less available, mothers break off into smaller groups and forage for food with their babies.

“But when they’re doing that, they are also limiting the ability of their young ones to play with others, and the moms become the primary playmates,” Kris Sabbi, who led the study, said. “They’re trading off that lower feeding competition in the larger group for more time and energy being spent playing with their little ones.”

This makes chimpanzees unique because, generally, animals don’t play with their children. The children usually play with each other.

“We were surprised to learn from our colleagues who study other social species that while play by young animals is near universal, adults play rarely, even with their own offspring,” Emery Thompson, a co-author on the study, said. “One hypothesis is that play stops being useful for animals who have completed their cognitive and motor development but our results suggest an alternative explanation: Animals in nature have too many competing priorities, particularly when resources are scarce. Adults opt for less costly forms of affiliation, like huddling together or grooming…”

“As evolutionary anthropologists, we are motivated to consider whether similar circumstances– prolonged development, since chimpanzees take 15 years to grow up, and periodic separation from other group members – may have made play between adults and children the norm in our own species,” she continued. “These findings also raise the question of whether play between adults holds any special significance, for example, as a way to reinforce a particularly beneficial relationship, or whether our brains evolved to find play rewarding because it is so important for our children.”

Sabbi also noted that chimps may play with their mother if they think the other chimps are playing too rough.

“If they’re playing with somebody and it starts to get a little bit too rough, they’ll switch it up and go back to playing with mom because, at the end of the day, it’s a very safe place,” Sabbi said. “If we compare to humans, it’s very easy to find lots of evidence in the child psychology literature for how important it is for human mothers and fathers to be playing with their children, especially at really young ages. Moms and dads are important first play partners before kids branch out into their own social networks.”

The researchers concluded that one reason why animals may not play isn’t because doing so lacks utility but because it uses time and energy. Additionally, the researchers wonder if the results are similar among closely related primates, the release said.

Kris Sabbi, a 2020 University of New Mexico Ph.D. graduate, who is currently a college fellow of Human Evolutionary Biology at Harvard University, led the study.

Sabbi led the study with her former doctoral associate, Zarin Machanda, an assistant professor of Anthropology and Biology at Tufts University. Additionally, UNM anthropology professors Melissa Emery Thompson and Martin Muller, plus UNM Anthropology graduate student Megan Cole and Isabelle Monroe, UNM graduate and research lab coordinator at the University of Michigan, were co-authors on the study.

A press spokesman for Tuft Univesity told The Center Square by email that the following entities provided grant funding for this research: the National Science Foundation, the National Institute on Aging, the Leakey Foundation, and the Wenner-Gren Foundation.