Reputation: Hyenas are ugly villains that only eat dead things, sometimes lions, sometimes even humans. Then they whoop with laughter. Despicable. They are also hermaphrodites, aren't they?

Reality: Spotted hyenas deserve respect not contempt. More often than not, they hunt down their prey rather than scavenge. They are fabulously intelligent, with massive brains and one of the most complex social set-ups of any carnivore. Females dominate males and have no vaginal opening, but they do sport an impressive, fully erectile clitoris. What's not to like?

This article is for my mother-in-law. A couple of weeks ago, she came by our house and started ranting about hyenas and what evil, good-for-nothing creatures they are. Like a good son-in-law, I begged to differ. This stereotype, I suspect, may prevent us from seeing hyenas as they really are.

Lions scavenged spotted hyena kills more often than the other way round

One of the most oft-touted tropes about hyenas is that they are scavengers, stealing most of their food from more upstanding species like lions and (according to Pliny the Elder) sometimes even digging up graves in search of human corpses.

That is wrong, at least for spotted hyenas (Crocuta crocuta). Working in the Ngorogoro Crater in Tanzania back in the 1970s, zoologist Hans Kruuk found that the lions scavenged spotted hyena kills more often than the other way round.

"There is no population, anywhere in Africa, where they don't hunt down at least 50% of their own food," says spotted hyena expert Kay Holekamp of Michigan State University in East Lansing, US. The scavenger stereotype may apply to striped and brown hyenas, which both eat a lot more carrion, but it can hardly be attributed to an animal capable of taking down an adult wildebeest four times its size.

Spotted hyenas also have far larger brains than the other two species, even controlling for their much larger skulls.

We know this because Holekamp and her colleagues have passed dozens of skulls through a CT scanner to create virtual images of hyena brains. This also revealed that spotted hyenas have particularly enlarged forebrains, the region involved with complex decision-making.

This makes sense because spotted hyenas are often found in very large, very fluid groups. The smallest spotted hyena clans are about the same size as a big lion pride or big wild dog or wolf pack. But these will often coalesce into huge aggregations.

"The biggest gathering we've ever seen had 72 animals in it," says Holekamp. Another clan she is studying contains 130 individuals, though these have not been observed in the same place at the same time. "This is bigger by an order of magnitude practically than any other carnivore group."

Imagine trying to keep track of 130 different hyenas

Given this, it should come as no surprise that the vocal repertoire of spotted hyenas is several times as rich as that of other hyenas, or for that matter, lions.

One of their calls is the famous "whoop". To the uninitiated, there is something undeniably sinister about this call, particularly when it comes in the pitch darkness of an African night. But to those who understand spotted hyenas, it is simply an effective way for them to establish and maintain contact with each other over a distance.

Each hyena uses sounds, smells and visual cues to recognise others in their clan. "Imagine trying to keep track of 130 different hyenas," says Holekamp. "That's quite a cognitive task but they seem able to do it just fine."

Who wears the trousers?

Spotted hyena society is also notable for the dominance of its females over its males. This is not the case in the other two, more traditionally familial hyena species. Amongst female spotteds, there is a strict hierarchy. The highest ranking female gets first dibs on any kills, which helps her to reproduce more quickly and successfully than females further down the pecking order.

But perhaps the strangest thing about female spotted hyenas is their reproductive anatomy. Internally, there's not much to set them apart from other mammals. But to say that their external genitals are far-out is to put it mildly.

"The clitoris is enormously elongated to form this fully erectile pseudopenis through which they urinate, copulate and give birth," says Holekamp. This is a sentence she has clearly delivered before because she fires this volley of explicit words at me in less than 8 seconds: I timed it.

"It's the only female mammal that has no external vaginal opening," she adds, just to confuse me further. "That is something that is totally unique."

Neither male nor female?

So unique, in fact, that for centuries people assumed the spotted hyena had to be a hermaphrodite.

The clitoris is enormously elongated to form this fully erectile pseudopenis

In a way, this is understandable. If you saw a spotted hyena loping back to its den with clearly distended mammary glands, you would probably guess it was a female. When the same milk-laden animal welcomed a fellow clan member with a massive phallic erection, you might feel less certain. "That confused people for a very, very long time," says Holekamp.

During sexual intercourse, this organ is flaccid but the male still has to insert his erect penis into the clitoris. If this sounds like it might be uncomfortable, then just imagine what it's like to deliver a 1.5-kilogram foetus from the same orifice.

What is this bizarre genital apparatus about? A lot of very clever people have thought long and hard about precisely this question. But "nobody really understands yet quite what it's there for," says Holekamp.

One possibility is that it helps the members of a clan recognise each other. Spotted hyenas will often perform a "greeting ceremony": standing side-by-side and head-to-tail, each sniffing the erected phallus of the other. But this seems a little over the top. If a hyena can recognise clan-mates by more conventional sensory means, does she really need a pseudopenis?

Angry girls

A more likely alternative is that female hyenas have been naturally selected for their size and aggression. Unusually high levels of testosterone during early development could make their genitalia develop in this unusual way.

It is also possible that such a bizarre reproductive tract gives a female some control over the father of her offspring. Not only does it make it challenging for a male to insert his penis, but the bladder also empties into the same channel. So a female that has just mated with a male can easily change her mind. "She always has the option of flushing the whole system," says Holekamp.

In case you're wondering, I did not share any of this lurid detail with my mother-in-law.

Tweetable facts about spotted hyenas

Spotted hyenas are not the same as striped hyenas or brown hyenas.

Spotted hyenas are not scavengers, but hunt down at least 50% of their own food.

Spotted hyena clans can contain up to 130 individuals, more than an order of magnitude greater than any other carnivore.

The female spotted hyena urinates, copulates and gives birth through her clitoris. Ouch.