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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.
And you’ve 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 clanmates
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.
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