Using 27 years of detailed data on hyena social interactions, a team led by Penn biologists nailed down a pattern of social network inheritance and its implications for social structure, rank, and survival.
Hyenas are a highly social species, living in groups that can number more than 100. But within their clans, there is order: A specific matrilineal hierarchy governs societies in this species where females are dominant to males.
While researchers have intensively studied the social structure of hyenas and other animals, it’s only recently that scientists have begun to investigate how this structure arises. A new study led by Penn biologists, which relies upon 27 years of detailed observations of hyena social behavior collected by researchers at Michigan State University, pulls back the curtain on how social order comes to be.
Their findings show that hyenas inherit their mother’s social networks, so their social connections resemble their mother’s. However, offspring of higher-ranking individuals more faithfully replicate their mother’s interactions, winding up with social networks that more closely resemble their mother’s than do offspring of females that rank lower on the clan’s social ladder. The team reported their findings in the journal Science.
“We knew that the social structure of hyenas is based in part on one’s rank in the agonistic hierarchy, which we know is inherited from mothers,” says Erol Akçay, a study coauthor and associate professor in Penn’s School of Arts & Sciences. “But what we found, that affiliative, or friendly interactions, are also inherited, hadn’t been shown.”
“This is a very simple process of social inheritance that we show works very, very well,” says Amiyaal Ilany, a senior lecturer at Israel’s Bar-Ilan University. “Individuals that were born to higher rank are more accurate in their inheritance, and they have good reason to do so. It fits well with what is already known about inheritance of rank. There are very strict rules about what place you sit in the hierarchy if you are a hyena.”
The work builds on a theoretical model of social network inheritance Akçay and Ilany developed in 2016. According to that simple framework, animals establish their networks by “social inheritance,” or copying their mother’s behaviors. The model fits well with snapshots of real-world social networks from not only hyenas but also three other social species: bottle-nosed dolphins, rock hyrax, and sleepy lizards.
In the new work, the team aimed to refine their…