NIMBioS Study: It’s Best to Make Friends of Friends—Just Ask the Spotted Hyena

Networked hyenas (Photo: Amiyaal Ilany)

Networked hyenas (Photo: Amiyaal Ilany)

Bonding with a friend of a friend is something most humans gravitate toward naturally—hence Facebook’s ongoing prompts of people for you to “friend.”

If animals could use Facebook, the spotted hyena would be a natural.

A new study from UT’s National Institute for Mathematical and Biological Synthesis (NIMBioS) shows that the four-legged predator seems to instinctively know the benefits of this type of social bonding.

The study, which looks at the social network structure of the spotted hyena, appears today in the journal Ecology Letters. It is available online.

Hyenas, which can live up to twenty-two years, typically live in large, stable groups known as clans, which can include more than 100 individuals. Socially sophisticated animals, hyenas can discriminate maternal and paternal kin from unrelated hyenas. They are selective in their social choices and tend not to form bonds with every hyena in the clan, but rather prefer the friends of their friends, the study found.

Researchers collected more than 55,000 observations of social interactions of spotted hyenas over a twenty-year period in Kenya, making this one of the largest studies of social network dynamics of any nonhuman species. They found that cohesive clustering where an individual bonds with friends of friends—something scientists call “triadic closure”—was the most consistent factor influencing the long-term dynamics of the social structure of spotted hyenas.

Individual traits, such as sex and social rank, and environmental effects, such as the amount of rainfall and the abundance of prey, also matter in social structure, but the ability of individuals to form and maintain social bonds in triads was key, according to the study.

“Cohesive clusters can facilitate efficient cooperation and hence maximize fitness, and so our study shows that hyenas exploit this advantage,” said lead author Amiyaal Ilany, who conducted the research as a NIMBioS postdoctoral fellow. He is now at the University of Pennsylvania. “Interestingly, clustering is something done in human societies, from hunter-gatherers to Facebook users.”

The study found that hyenas follow a complex set of rules when making social decisions. Males follow rigid rules in forming bonds, whereas females tend to change their preferences over time. For example, a female might care about social rank at one time, but then later choose based on rainfall amounts.

Knowing why and how these animals form lasting relationships can help scientists better understand cooperation patterns and the consequences of sociality in other species.

The researchers used a new, more comprehensive method than those used in earlier studies, a type of mathematical modeling typically found in sociology, to arrive at their findings about the spotted hyena.

This more dynamic approach represents a major advancement over past study methods, allowing researchers to evaluate the simultaneous effects of multiple factors—environmental, individual, genetic, and structural—on network dynamics. It also gave the researchers a peek into how or why the social structure changes over time and allowed them to isolate the factors that shape the structure.

NIMBioS is a National Science Foundation–supported center that brings together researchers from around the world to collaborate across disciplinary boundaries to investigate solutions to basic and applied problems in the life sciences.

To learn more about NIMBioS, visit the website.

CONTACT:

Catherine Crawley (865-974-9350, ccrawley@nimbios.org)

Lola Alapo (865-974-3993, lalapo@utk.edu)