Bonobo moms help their sons secure mating opportunities

Scientists at the Max Planck Institute for Evolutionary Anthropology determined the assistance of their mother improves a male's chance of becoming a father by a factor of three.

"This is the first time that we can show the impact of the mother's presence on a very important male fitness trait, which is their fertility," primatologist Martin Surbeck said in a news release. "We were surprised to see that the mothers have such a strong, direct influence on the number of grandchildren they get."

Researchers observed the behaviors of wild bonobo populations in the Democratic Republic of Congo, as well as wild chimpanzee populations in the Ivory Coast, Tanzania and Uganda. Surbeck and his colleagues found both chimp and bonobo moms advocate for their sons during male-male combat.

But researchers observed bonobo moms taking their advocacy a step farther. In the Congo, bonobo moms guarded the mating attempts of their sons, preventing competing males from intervening. Bonobo moms also interrupted the mating attempts of other males.

Additionally, bonobo mothers used their elevated status in the primate's matriarchal society to gain their sons access to places of social significance, increasing the odds of their sons gaining and maintaining high social status. Males with greater social status have a better chance of mating with fertile females.

In bonobo society, mom's help isn't typically available to daughters.

"In bonobo social systems, the daughters disperse from the native community and the sons stay," Surbeck said. "And for the few daughters that stay in the community, which we don't have many examples of, we don't see them receiving much help from their mothers."

The new research was published this week in the journal Current Biology.

Currently, scientists theorize mom's main motivation is genetic continuity, but researchers hope longer, more comprehensive studies of bonobo society could provide additional insights into the benefits of aggressive mothering.

It's possible, scientists suggest, that by avoiding the added physiological burden of birthing more children, protective moms can increase their lifespan. The phenomenon could explain why human females lose their ability to have children fairly early in life, compared to other mammals.