Friendship is extremely important to humans, and we're often picky about who we choose to befriend; new research suggests spotted hyenas feel the same way.

A team of researchers collected 55,000 observations of social interactions of Kenyan spotted hyenas over a 20 year period, and discovered a high prevalence of individual bonds with "friends of friends," National Institute for Mathematical and Biological Synthesis (NIMBioS) reported.

This phenomenon is called "triadic closure," and was found to be the key factor affecting the dynamics of the social structure among the spotted hyenas.

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

Hyenas generally live in large groups, dubbed clans, that can encompass as many as 100 individuals. Within these clans, the hyenas are choosy with their social bonds, and are more attracted to friends of their friends. The study revealed these hyenas follow a complex set of rules when making social decisions; males follow more rigid guidelines while females change their preferences over time.

"In spotted hyenas, females are the dominant sex and so they can be very flexible in their social preferences. Females also remain in the same clan all their lives, so they may know the social environment better. In contrast, males disperse to new clans after reaching puberty, and after they disperse they have virtually no social control because they are the lowest ranking individuals in the new clan, so we can speculate that perhaps this is why they are obliged to follow stricter social rules," said co-author Kay Holekamp, a zoologist from Michigan State University.

The findings were published in a recent edition of the journal Ecology Letters.