Inheriting Friends from Mother’s Key to Hyena’s Success | MSU Today


In the wild, inheriting beneficial physical traits can be the difference between a long and a short life. But for the spotted hyena, another type of inheritance, which has nothing to do with genetics, is extremely important for health and longevity – social networks inherited from their mothers.

A new study, based on 27 years of observational data from University of Michigan Emeritus professor Kay holekamp, extends a previously established theoretical model of spotted hyena social networking to show how these networks emerge, how long they last, and how they affect a hyena’s life trajectory.

The article is featured as the cover of the journal Science.

MSU Distinguished Professor Kay Holekamp has collected over 30 years of detailed observational data on hyenas.

“There are a lot of species where the genetic inheritance of being bigger and stronger allows an animal to dominate, but that doesn’t happen in the society of hyenas,” said Holekamp, ​​professor at the integrative biology department and director of the interdisciplinary program in Ecology, evolution and behavior who co-authored the document. “We see tiny cubs towering over large huge males, so we know body size is not a good predictor of who will be socially dominant in spotted hyenas.”

Co-authors Erol Akçay, associate professor at the University of Pennsylvania and Amiyaal Ilany, lecturer at Israeli Bar-Ilan University, used sophisticated modeling techniques of social evolution to establish general theoretical principles on how social networks among hyenas are transmitted. But to test and extend the model, they needed data from nature.

“The basis for this article was laid when Amiyaal requested access to our data on hyenas because he wanted to model association patterns in hyenas, and I’m always happy to share data,” he said. declared Holekamp, ​​of which research group has close sighting records for several generations of hyenas from the Masai Mara National Game Reserve in Kenya.

One photo shows a group of several spotted hyenas - animals with golden fur dotted with darker spots.

Several hyenas lean against each other and engage in social sniffing, an affiliate behavior that serves to promote social bonds among clan members. The offspring of the females in this photo are likely to associate with their mother’s close associates even after their own mother has died, which is a key point of the article. Credit: Lily Johnson-Ulrich

By meticulously tracking hundreds of individual hyenas based on their specific spot patterns, social media could be determined by proximity – who spent time with whom, how far, and for how long. By combining this rich set of data with the models of social evolution developed by Akçay and Ilany, the team was able to show that, in a remarkable way, baby hyenas become very early friends with their mother’s relatives.

“We knew that the social structure of hyenas is based in part on rank in the agonistic hierarchy, which we know is inherited from mothers,” Akçay said. “But what we found, whether affiliate or friendly interactions are also inherited, had not been shown.”

The networks of mothers and their offspring are similar in the beginning because small hyenas stay close to their mothers for the first two years of their life. But the researchers noticed that even though the young hyenas stopped spending so much time near their mothers, they continued to maintain similar networks. This was especially true for female offspring, who usually remain a member of the clan for life.

“We have data in some cases showing that the network similarity between mothers and offspring, especially female offspring, was still very high after about six years,” Ilany said. “You might not see your mom that often, or she might even have passed away, but you still have similar friends. “

It is important to note that higher-ranking mothers imprinted their social media on their cubs more accurately and for longer than lower-ranking mothers, and these networks had a direct effect on lifespan and reproductive success.

A mother spotted hyena rests behind three of her young.

A female collared spotted hyena with her litter of two cubs and another cub in the clan communal den in the Masai Mara National Reserve in Kenya. Credit: Phoebe Parker-Shames

Mother-offspring pairs with more similar social networks lived longer, the team found, noting how factors other than genetics influence key evolutionary outcomes.

“One explanation for why social media inheritance works better for high rank than low rank hyenas may be that lower rank females tend to fend for themselves more often to avoid competition with high rank hyenas. higher rank, so that their little ones have less learning. opportunities that top female cubs rank, ”Holekamp said. “It shows the beauty of the hyena fusion-fission society. The lower ranks can make the most of a bad situation by using separation to distance themselves from their competition.

The article is just one example of how the unprecedented amount of data collected by Holekamp’s research group since the 1980s has led to an explosion of new research and insight into the social evolution of hyenas. .

“The long-term nature of our research allows scientists to answer questions about the fitness consequences you can’t do with a long-lived organism unless you sit down and watch them year after year. “said Holekamp. “We’re at a point where we have some really fabulous fitness data in addition to documenting years of interesting behavioral phenomena, and we can follow individuals over time to find out what the consequences of these behavioral patterns are on fitness. . “

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