In spotted hyena societies, social networks — passed from mothers to their offspring — are essential to hyena life and survival.
According to a new study published in the July 16 issue of Science, the social relationships of juvenile spotted hyenas are similar to those of their mothers and the degree of similarity increases with the mother's social rank. The findings suggest that the inheritance of social networks and the strength of mother-offspring bonds may play a key role in shaping social structures and the fitness of individual animals across generations in the wild.
"We've all realized how important social networks are due to the pandemic," said Amiyaal Ilany, senior lecturer at Bar Ilan University, Israel and lead author of the study. "Social networks affect many aspects of life, in both humans and animals, and that's why it is so important to understand how these networks form and change."
The findings could be used to understand further general processes that influence other networks and systems in the wild, including population dynamics for conservation efforts, and show the importance of population stability in social species.
"You can't just release a bunch of individuals into the wild and expect them to get along well," said Ilany.
Social bonds are important to many aspects of life, including health, survival and reproductive success. However, the general mechanisms that determine and perpetuate social structure in wild animal populations remain unclear.
One proposed model, termed social inheritance, suggests that an offspring's social ties tend to resemble those of their parents — particularly those of the mother. While inheritance of social status and all its associated intergenerational costs and benefits are well recognized in humans, previous studies have revealed similar processes in other highly social species, such as rhesus macaques and African elephants.
Ilany and a team of researchers evaluated the role of social inheritance in spotted hyena society, which is female-dominated and highly structured. According to Ilany, wild hyenas provide an exceptional example of a complex society in animals that maintain long-term relationships.
Spotted hyenas — perhaps the most social of carnivorous mammals — live in stable groups or clans, which resemble the societies of baboons or macaques in terms of size and structure. Typically, hyena clans live in communal dens and contain several matrilineal kin groups that span multiple generations. While clan mates compete for killed prey, high-ranking individuals often maintain priority access to food.
Combining social network analysis and a unique transgenerational dataset comprised of 73,767 observations of social interactions among a population of wild hyenas spanning 27 years, the researchers discovered that social network inheritance is prominent in wild hyena society.
The authors found that the relationships of offspring with other hyenas are similar to those of their mothers and that these similarities persist for many years, even after the offspring grow older and independent from their mothers.
According to Ilany, the most intriguing and surprising findings were that maternal rank — the mother's status within the clan — and the strength of the bond between a mother and her offspring predicted both the strength of social inheritance and the long-term survival of the pair.
"The relationship is a bit complex," said Ilany.
Offspring of high-ranked mothers survive better if they copy their mother's social behavior accurately and form relationships with the same clan members. However, the opposite is true for offspring of low-ranked mothers.
"I see this as a kind of 'silver spoon effect' — if you are born to successful parents, do what they do. If you are born to losers — don't follow them," said Ilany. "They should change to survive."
However, since the mother-offspring social similarity also appears to depend on the strength of the maternal bond, Ilany notes that the effect of social inheritance on survival may also be correlative.
Ilany believes that the study shows that inherited traits some researchers assume to be genetic, such as the tendency to socialize and organize socially, can rather be explained by simple, social copying processes, illustrating why the social environment is so vital to an individual's life.