Nav: Home

Female chimps with powerful moms are less likely to leave home

January 20, 2020

DURHAM, N.C. -- In chimpanzee society, males spend their entire lives in the group where they were born, cooperating to defend their territory, while females tend to move away. But some chimp females seem less willing to cut the apron strings.

New findings from researchers at Duke University and North Carolina State University show that female chimpanzees with high-ranking mothers are more likely to be homebodies.

The study suggests that the perks of having a powerful mom can make it worthwhile for some females to stay and reproduce in the same group where they grew up, despite the risks of inbreeding with male relatives.

For the research, appearing Jan. 20 in the journal Current Biology, primatologists Kara Walker and Anne Pusey analyzed 45 years of dawn-to-dusk observations for 31 female chimpanzees born in Gombe National Park in Tanzania, where Pusey began working with Jane Goodall in 1970.

Chimps are unusual among mammals in that daughters, not sons, typically pick up their roots at puberty and move away from their families. But in Gombe National Park, some chimpanzee females stay put instead of moving out.

Leaving home is hard, and no less so for a chimp. Immigrants risk a great deal -- leaving behind the familiar faces and comforts of home to strike out alone on a perilous journey, only to face multiple challenges upon arrival. Compared to stay-at-home females, those who leave are often attacked by resident females when they arrive in a new group. They also get a later start on motherhood.

So why do movers move away and stayers stay put? "I've always been intrigued by that question," said Pusey, professor emeritus of evolutionary anthropology at Duke. "It has driven my research for decades."

Differences between the sexes in migratory patterns are widespread in mammals and birds, Pusey said. She and colleagues first noticed the pattern at Gombe in the 1970s, but because female chimpanzees don't leave home until between the ages of 11 and 13, it would take years of observation to unravel the reasons behind it. Now, thanks to Pusey's efforts to compile and digitize the data and put it all in one database, researchers are starting to find answers.

In the study, the team found very little difference between females who left and those who stayed in terms of things like diet quality, crowding, or the number of unrelated males around when females reached maturity, which suggests they don't leave due to competition for food or lack of suitable mates.

It was only when the researchers looked more closely at the females' family members that the split began to reveal itself: specifically, they found that females with more brothers were more likely to leave -- presumably because they risk inbreeding if they stay.

Brothers and sisters from the same mom usually show little interest in each other, avoiding sex with close kin. But there are exceptions, said Walker, a research assistant professor of behavioral ecology at North Carolina State University. High-ranking males have been known to coerce their sisters into mating with them. For the chimpanzees at Gombe, only one of four known offspring of such close matings made it to adulthood.

"Breeding with a brother is a pretty costly mistake," Walker said.

The results confirm a decades-old hypothesis, that in many animals that live in groups, the hazards of inbreeding push one sex or the other to start their families elsewhere. But the study also points to a countervailing force that compels some female chimpanzees to stay put: mom. The researchers found that females with high-ranking moms on hand were more likely to stay rooted.

Yes, being the unwitting target of a brother's misdirected advances might be a pain, but for some, the risk might be offset by the benefits of having a built-in support system.

Living close to mom means she's able to provide help, such as by sharing prime foraging spots, the researchers say. And whereas females who move away enter their new groups at the bottom of the pecking order, females with powerful moms who choose to stay put benefit from their mother's social clout and "cut in line."

Pusey thinks a lot can be learned about the evolution of migratory patterns in humans by studying chimpanzees. Our species also typically sees young women more likely than young men to leave home for marriage.

Even in chimps, she says, "it's sometimes better for females to stay," which "suggests that the benefit of having mom around is pretty universal."
-end-
This research was supported by the Jane Goodall Institute, the National Science Foundation (DBS-9021946, SBR-9319909, BCS-0648481, IOS-LTREB-1052693), the National Institutes of Health (R01 AI058715, R01 AI50529, R01 AI58715, P30 AI27767), the University of Minnesota, Duke University, the Leakey Foundation and the Margot Marsh Biodiversity Fund.

CITATION: "Inbreeding Risk and Maternal Support Have Opposite Effects on Female Chimpanzee Dispersal," Kara K. Walker and Anne E. Pusey. Current Biology, Jan. 20, 2020. DOI: 10.1016/j.cub.2019.11.081.

Duke University

Related Chimpanzees Articles:

For chimpanzees, salt and pepper hair not a marker of old age
Silver strands and graying hair is a sign of aging in humans, but things aren't so simple for our closest ape relatives--the chimpanzee.
In the wild, chimpanzees are more motivated to cooperate than bonobos
Scientists investigated cooperation dynamics in wild chimpanzees (Tai, Ivory Coast) and bonobos (LuiKotale, DCR) using a snake model.
A rare heart bone is discovered in chimpanzees
Experts from the University of Nottingham have discovered that some chimpanzees have a bone in their heart, which could be vital in managing their health and conservation.
In chimpanzees, females contribute to the protection of the territory
Researchers of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, extensively studied several neighboring groups of western chimpanzees and their findings reveal that females and even the entire group may play a more important role in between-group competition than previously thought.
Cultural diversity in chimpanzees
Termite fishing by chimpanzees was thought to occur in only two forms with one or multiple tools, from either above-ground or underground termite nests.
Similar to humans, chimpanzees develop slowly
Researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have systematically investigated developmental milestones in wild chimpanzees of the Taï National Park (Ivory Coast) and found that they develop slowly, requiring more than five years to reach key motor, communication and social milestones.
The genome of chimpanzees and gorillas could help to better understand human tumors
A new study by researchers from the Institute of Evolutionary Biology (IBE), a joint center of UPF and the Spanish National Research Council (CSIC), shows that, surprisingly, the distribution of mutations in human tumors is more similar to that of chimpanzees and gorillas than that of humans.
Crops provide chimpanzees with more energy than wild foods
A University of Kent study has found that cultivated foods offer chimpanzees in West Africa more energetic benefits than wild foods available in the region.
The growing pains of orphan chimpanzees
Using long-term behavioral and hormonal data from wild chimpanzees in the Taï Forest, Côte d'Ivoire, researchers from the Taï Chimpanzee Project at the Max Planck Institute for Evolutionary Anthropology, have revealed that mothers may be shaping pre-adult growth and offspring muscle mass even without direct provisioning.
How humans and chimpanzees travel towards a goal in rainforests
How do human-unique ranging styles, like large home range and trail use, influence the way we travel to our goals?
More Chimpanzees News and Chimpanzees Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Debbie Millman: Designing Our Lives
From prehistoric cave art to today's social media feeds, to design is to be human. This hour, designer Debbie Millman guides us through a world made and remade–and helps us design our own paths.
Now Playing: Science for the People

#574 State of the Heart
This week we focus on heart disease, heart failure, what blood pressure is and why it's bad when it's high. Host Rachelle Saunders talks with physician, clinical researcher, and writer Haider Warraich about his book "State of the Heart: Exploring the History, Science, and Future of Cardiac Disease" and the ails of our hearts.
Now Playing: Radiolab

Insomnia Line
Coronasomnia is a not-so-surprising side-effect of the global pandemic. More and more of us are having trouble falling asleep. We wanted to find a way to get inside that nighttime world, to see why people are awake and what they are thinking about. So what'd Radiolab decide to do?  Open up the phone lines and talk to you. We created an insomnia hotline and on this week's experimental episode, we stayed up all night, taking hundreds of calls, spilling secrets, and at long last, watching the sunrise peek through.   This episode was produced by Lulu Miller with Rachael Cusick, Tracie Hunte, Tobin Low, Sarah Qari, Molly Webster, Pat Walters, Shima Oliaee, and Jonny Moens. Want more Radiolab in your life? Sign up for our newsletter! We share our latest favorites: articles, tv shows, funny Youtube videos, chocolate chip cookie recipes, and more. Support Radiolab by becoming a member today at Radiolab.org/donate.