Spotted hyena daughters inherit rank, resources, and a taste for power

Among people, it is common knowledge that privilege is often inherited. But according to new findings, hyenas also inherit resources and status, and not just their forebears’ genes, from their parents.

The findings were published recently in Science Advances — and they challenge the traditional evolutionary theories that assume males always face greater reproductive competition.

In the animal kingdom, the males are generally considered to be the dominant sex. They are stronger and more competitive. But spotted hyenas buck this trend.

Scientists at the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) in Berlin and the Institute of Evolutionary Science of Montpellier have found that in spotted hyenas, females dominate males not because they are bigger or stronger but because they have larger networks of social alliances.

The study also showed that female hyenas face more competition shaped by the inheritance of social rank across generations.

Marta Mosna, the lead author of the study and a researcher at Leibniz-IZW and the Ngorongoro Hyena Project, observed during her field visit in Africa that “male hyenas do not compete so much with each other”. Instead, they were found spending their time following the alpha female, the highest-ranking female hyenas, around.

“The males follow them wherever the female goes,” Ms. Mosna said. “They are staying close to her, spending a lot of time watching her, trying to connect with her, and trying to be friends with her.”

On the other hand, the competition is more fierce among the females.

“This is not really what you would expect for the classical sex role that Darwin-Bateman predicts,” she said.

The Darwin-Bateman hypothesis proposes that reproductive inequality is greater among males. That is, between males and females, the males can father more offspring than females and this is why they compete more among themselves for access to mates. In mammals, the females also invest more in each reproductive event than males do — since they bear the physiological costs of pregnancy and lactation — they are more selective about mating. These predictions, formalised as the Darwin-Bateman paradigm, have been confirmed across many mammalian species.

However, among spotted hyenas, the researchers found the females killing off the cubs of other females, despite all living in a matrilineal society in which the individuals were related to each other.

These and other observations supported the researchers’ conclusion that the daughters of ‘elite’ families could build powerful family lineages over time — thus also challenging one of evolutionary biology’s classic paradigms.

For their study, the researchers studied hyenas belonging to eight resident clans in the Ngorongoro Crater in Tanzania. Their work spanned 29 years of data, eight generations, and 2,743 wild spotted hyenas.

The team used faecal samples to track paternity. These samples contained epithelial-rich mucus. “We need DNA information, which we normally take from the mucus around the faeces,” Dr. Mosna said. “We need to look at the males and wait for him to defecate. And then, when he leaves, be sure that this was his poop to do paternity analysis.”

“It is not always easy,” she continued. “Sometimes they even defecate in the water, and then it is gone, or sometimes after they eat it is a bit too liquid — it is not very pleasant to put your hand on. It can also be a bit challenging, but fortunately, our field assistants are very well trained and very good with it.”

For one clan that the team called ‘Lemala’, the researchers pieced together a 30-year genealogical tree and found that almost all the living members had descended from a single founding female lineage.

This led them to investigate how such extreme reproductive inequality could arise, which in turn led to the idea of the social inheritance of rank: since a female’s social position is passed to her daughters, it could give that lineage an advantage increasing across generations.

The youngest daughter born to an alpha female inherits her mother’s social status and also benefits from better access to food, allies, and breeding opportunities. Over generations, these benefits accumulate, allowing a few privileged female lineages to produce more descendants.

“Inheriting the privilege … means that you have better access to food and nutrition. They grow faster and survive longer. They also have a better position in the social network, which is also very important for hyenas,” Ms. Mosna said.

“This research teaches us that nothing is fixed. Sex roles are not fixed, like how a male or a female should behave; how our society should behave is not fixed by genetics. Only social processes can actually change society in a meaningful way.”

“This is a terrific paper that breaks a lot of new ground and serves as a powerful testament to the value of long-term field studies,” Kay E. Holekamp, a Michigan State University distinguished professor who was not involved in it, said.

The researchers are now exploring whether similar patterns of socially inherited reproductive inequality occur in other animal species. They have said they also want to investigate whether female hyenas invest differently in sons and daughters depending on their social rank. High-ranking females may invest more in daughters to pass on their privileged position while lower-ranking females may favour sons, so they can leave the clan and reproduce elsewhere, Ms. Mosna said.

“This study has broad implications for how we understand animal societies: social structures can transmit advantages across generations and thereby shape competition, inequality, and evolutionary outcomes,” Amiyaal Ilany of Tel Aviv University said.

“It also shows why inheritance should not be viewed as purely genetic. Socially inherited rank, relationships, and access to resources can have lasting effects on fitness and on the composition of future generations.”

Kavi Bharathi R. is a science writer based at the Indian Institute of Science, Bengaluru.