In Kenya, a spotted hyena relaxes with her 12- to 14-week-old cubs, who will inherit her allies.
Suzi Eszterhas/Minden Pictures
In hyenas as well as humans, it pays to be born to high-ranking parents. A new study reveals how power is passed down in these matriarchal mammals: Elite hyena cubs cultivate their mom’s friends, who help keep them fed and protected throughout their lives.
The work drives home the role moms and dads play in shaping the social world of their children, says Josh Firth, a social networks researcher at the University of Oxford who was not involved with the study. “We tend to think about who we are connected to as a product of our doing, but it’s a product of our parents as well.”
Chimpanzees, hyenas, and other social animals live in hierarchical societies. Those at the top eat first, and are typically surrounded by a gang that protects them from other members of their species that try to challenge their status. High rank tends to be inherited, but it’s been unclear how subsequent generations end up with the same type of ruling clan their parents do. Do they recruit their own powerful allies, or inherit them?
Erol Akçay, a theoretical biologist at the University of Pennsylvania, and behavioral ecologist Amiyaal Ilany, now at Bar-Ilan University, decided to analyze the work of Kay Holekamp. A behavioral ecologist at Michigan State University, Holekamp’s team had been following the lives of a clan of spotted hyenas (Crocuta crocuta) in Kenya for almost 30 years.
Day after day, the researchers have recorded the activity of the hyenas, including their interactions with and proximity to other hyenas, to understand the species’ behavior and ecology. They have also kept track of the pedigrees and social status of each female and its offspring.
Ilany used those data to reconstruct the social ties among these animals, based on their proximity to one another. Then they compared the social networks of mothers and their cubs.
Especially among high-ranking hyenas, then cubs developed the same friendships with the same families as their mother. The youngsters effectively inherited their mother’s social network, Ilany’s team reports today in Science. The more closely high-ranking cubs copied their moms’ social networks, the longer they lived. Cubs of lower status females, meanwhile, were best able to raise their survival odds by picking better allies than their moms did.
“If you are born to a high-ranking mother, you are better off if you copy what she’s doing,” Ilany explains. “But if you are born to a loser, then your lot is tougher, and you better do something else.”
“It’s a nice display of what’s going on in a real natural system,” Firth says. The same likely occurs in other social species, Akçay says. Firth, for example, has unpublished data documenting social inheritance in songbirds called great tits.
The work will change how researchers think about animal societies, Ilany says. “You can’t just look at social structure at one period of time,” Firth explains. “It’s just a snapshot, it might have been inherited from generation to generation.”