Social ties among spotted hyenas passed down from generation to generation

July 15 (UPI) -- A new study of social relations among spotted hyenas could offer insights into the evolution of social relations among humans.

The study -- published Thursday in the journal Science -- began with a theoretical model based on the idea that offspring inherit social ties from their parents, whether passively or through mimicry.

While working as a postdoctoral researcher at the University of Pennsylvania, Amiyaal Ilany worked with Erol Akçay, a theoretical biologist at Penn, to develop the social networking model.

To test the model, Akçay and Illany, now biologist at the Mina and Everard Goodman Faculty of Life Sciences at Bar-Ilan University in Israel, turned to the spotted hyena, a species that lives in hyper-competitive, hierarchical clans.

The model showed inherited social ties best explain the formation and maintenance of social relationships among hyena offspring.

Scientists supplied their model with data from a 27-year-long survey of spotted hyena clans in Kenya, led by Kay Holekamp of Michigan State University. The multi-decade study featured data from more than 74,000 social interactions.

"Social affiliations are, indeed, inherited within clusters of hyenas," Illany, lead author of the study, said in a press release. "The plethora of data on spotted hyenas that was collected by Kay Holecamp provided us with a golden opportunity to test the model we developed several years ago."

"We found overwhelming evidence that social connections of offspring are similar to those of the mother," Illany said. "A mother who has social affiliations with another hyena can connect her offspring to that hyena and the two, in turn, will form a social bond. Even after the mother-offspring bond itself weakens dramatically, the offspring still remain connected to their mother's friends."

The size of spotted hyena clans ranges from a handful of individuals to more than 100, depending on the availability of prey. For hyenas at the bottom of the social hierarchy, food can be very hard to come by.

"Rank is super important," said Akçay, who co-authored the study. "Spotted hyena live in a matriarchal society. Those born to a lower-ranked mother are less likely to survive and to reproduce."

Researchers found the offspring of higher-ranking females gain a leg up in the competition by forming social bonds similar to their mother.

The data showed offspring of high-ranking matriarchs replicated their mother's social relations more closely than lower-ranking offspring.

The model revealed a close relationship between survival and the ability to accurately replicate mom's social relations.

The findings support the hypothesis of Akçay and Illany that inheritance of social connections is key to maintenance of social structure.

The researchers said they suspect inheritance of social relations also has a positive influence on a group's social stability -- a reminder that factors beyond genetic fitness can influence a species' reproductive success and survival.

"A lot of things that are considered by default to be genetically determined may depend on environmental and social processes," said Ilany.