Chimpanzee daughters ‘less likely to leave home if mother is powerful’
Sometimes a strong chimp matriarch makes staying at home look like a better option than moving out.
Female chimpanzees with high-ranking mothers are less likely to leave the group, new research suggests.
In chimpanzee society, males spend their entire lives in the group they were born, working to defend their territory, while the females tend to move away.
However, new research suggests chimpanzee daughters whose mothers are top of the pecking order are more likely to cling to the apron strings, despite the risks of inbreeding.
According to the study published in the Current Biology journal, the perks of having a powerful mother can make it worthwhile for females to stay and reproduce in the same group they grew up.
Compared to stay-at-home females, those who leave are often attacked by resident females when they arrive in a new group, and also get a late start on motherhood.
Primatologists Kara Walker and Anne Pusey from Duke University in North Carolina, US, analysed 45 years of dawn-to-dusk observations for 31 female chimpanzees born in Gombe National Park in Tanzania, where Ms Pusey began working with Jane Goodall in 1970.
Unlike the majority of mammals, chimps are unusual in that daughters, not sons, typically move away from their families at puberty.
Researchers noted, however, that at Gombe National Park some females stayed put despite coming of age – particularly those with high-ranking mothers on hand.
They say being close to mother means she is able to help, such as by sharing prime foraging spots.
While females who move away join a new group at the bottom of the pecking order, those with powerful mothers who stay put benefit from social status, allowing them to cut in line.
Ms Pusey says “it’s sometimes better for females to stay”.
In terms of things like diet quality, crowding or the number of unrelated males around when females reached maturity, the team found very little difference between females who left and those who stayed.
The scientists say this suggests they do not leave due to competition for food or lack of suitable mates.
When they looked more closely at the females’ family members, scientists found female chimps with more brothers were more likely to leave – presumably because they risk inbreeding if they stay.
The study sets out that brothers and sisters from the same mother tend to show little interest in each other.
But there are exceptions where high-ranking males have been known to coerce their sisters into mating with them.
According to the research, only one of four known offspring of such close matings made it to adulthood.
Dr Walker said: “Breeding with a brother is a pretty costly mistake.”