Animals, too, cosy up to friends of friends

Bonding with a friend of a friend is something most humans do. But do animals too exhibit such behaviour?

Well, at least the spotted hyena seems to know the benefits of this type of social bonding, finds a study.

Hyenas typically live in large, stable groups known as clans which can comprise more than 100 individuals.

Socially sophisticated animals, these predators can differentiate between maternal and paternal kin from unrelated hyenas and are selective in their social choices, tending to not form bonds with every hyena in the clan.

They prefer the friends of their friends, the study found.

Researchers from University of Tennessee's National Institute for Mathematical and Biological Synthesis collected more than 55,000 observations of social interactions of spotted hyenas over a 20-year period in Kenya.

They found that cohesive clustering of the kind 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.

"Cohesive clusters can facilitate efficient cooperation and hence maximise 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.

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 at a later point in time make decisions based on rainfall amounts.

"In spotted hyenas, females are the dominant sex and so they can be very flexible in their social preferences," said co-author Kay Holekamp from Michigan State University.

In contrast, males disperse to new clans after reaching puberty.

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 study was published in the journal Ecology Letters.