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You can go to linode.com/scishow to learn more and get a $100 60-day credit on a new Linode account. [ intro ] There are a lot of animal species that get unfairly painted as villains in the stories we tell. Take the hyena, for example.

If most of what you know about them comes from a certain animated movie from the 90s, you might think of them all as sneaky, stupid, sidekick scavengers. But in the real world, things are a lot more complex. One hyena species lives in large social groups with a rigid social hierarchy of their own.

And unlike in The Lion King, their leaders are female. They also have matrilineal dynasties, with mothers passing their proverbial rule down to their daughters. So scientists have been trying to figure out how and why that happens, if it’s nature, or nurture.

And it turns as is often the case with this question, out it’s probably a bit of both. Female members of the species Crocuta crocuta, otherwise known as the spotted hyena, are pretty awesome. Each social group, or clan, can be made of over 120 members who live according to a rigid, female-dominated social hierarchy led by specific bloodlines that share resources, territories, and social networks.

But how do these females and their offspring maintain their social position in the clan? Physically, they’re bigger and more aggressive than males. Scientists have traditionally attributed both of these traits to a group of hormones called androgens which play an important role in the development of male sex characteristics.

You’ve probably heard of at least one androgen, testosterone. Androgens are produced by both males and females in any vertebrate animal species, but typically the males make more of them. In the case of spotted hyenas, there are several androgens that females tend to have in greater abundance than their male counterparts.

But things get a lot more complicated when it comes to testosterone. Normally, females have less testosterone circulating in their bodies than the males do. But that changes when they get pregnant.

Toward the end of a female hyena’s pregnancy, her androgen levels start to increase. And exposure to these extra hormones will shape the personality of the fetus for the rest of its life. This is the “nature” part of how spotted hyenas maintain their clan’s social hierarchy.

The amped-up androgen cocktail a baby hyena is exposed to before they’re born will permanently rev up their aggressive tendencies. Back in 2006, a team of scientists published research which showed that the higher up on the social ladder a mother hyena is, the more her androgen levels increase during pregnancy. So hyenas born to high-status mothers will go on to be more aggressive than those of low-status mothers, and therefore higher up the social ladder themselves.

That makes hyenas the first known mammals to use this technique to pass down their social status. Pretty cool. But this androgen exposure works for ramping up the aggressive tendencies for both female and male offspring.

So while it might help explain why spotted hyenas can maintain dynasties, keeping the same families in charge, the androgen increase during a mother’s pregnancy can’t fully help us explain why those dynasties are matriarchal. There has to be some kind of “nurture” component that helps female hyenas rule their clans, too. And for evidence of that, we turn to a study published in 2018.

Another group of scientists spent a decade tracking the aggressive interactions of eight spotted hyena clans in Tanzania, recording which hyena came out on top each time two individuals clashed. They monitored interactions between members in the same clan, as well as different clans, taking into account whether the members had grown up in those clans, or had immigrated into them. And they found that individual hyenas with more social support from their clan mates were more likely to dominate in one-on-one interactions, regardless of their sex.

But females came out on top because, on average, they had stronger social ties than males. The study found that hyenas usually support their relatives in any showdown between two individuals. A hyena’s social ties, and therefore its social status, ultimately come down to its blood relationships.

And most males leave their family and emigrate to another clan when they reach adulthood. Why would they do that? Well, it gives them an opportunity to find a mate that isn’t a sister or cousin.

And that increase in genetic diversity tends to produce healthier offspring, which a species kind of needs to stick around. The fact that female hyenas are the ones that tend to stay close to home probably contributed to the evolution of a female-dominated society. This is all super fascinating, so here’s to hyena moms, and the complex communities they raise their kids in.

Maybe it’s time for a Hollywood makeover. I’d definitely go see a movie called The Hyena Queen. Since SciShow videos are made for YouTube rather than Hollywood, if you learned anything that you want to look into further, you can always find links to the original research publications in the description down below.

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Thank you to Linode, to all of the hyena scientists and to you for learning with us. [ outro]