Hyenas just don't get any respect. They are considered smelly, dirty, ugly, and dangerous. It's true that they are scavengers, carrion-eaters, but so is the noble lion, when he can get away with it. They only scavenge when there is no other food, usually no more than 50% of the time (about the same as the lion). They are, in terms of beauty, perhaps an acquired taste. And certainly their huge mouthful of teeth and bone-crunching jaws provide an impressive display of killing power.

But hyenas, like all animals, have a place in the world, and underneath their fearsome exteriors lies... an equally fearsome interior. There really is no getting around it - they are scary animals with some very nasty habits. But they are fascinating as well. Hyenas have physical and social characteristics that are found in no other mammals, and once you learn about these animals... well, you may not love them, but you'll have to admit that they are interesting.

When hyenas were first discovered by explorers, it was thought that the males and females must look very different, as all the specimens spotted or shot were male. Therefore, the females must be different enough to look like another species entirely. Various other wild canids were considered for the role, but they all proved to have their own males and females. Observation of packs of hyenas in the wild (in the 1960s) revealed the information that the smaller males were submissive to the larger ones, but still no females. Then, surprisingly, mating occurred, apparently between two males, and pups were born. This caused a flurry of excitement. There are animals that are naturally born hermaphrodites (that is, animals that have both m ale and female sexual organs), and there are also animals that can change genders in certain conditions - but no mammals are known to fall into either category. Were hyenas the first known example of a hermaphrodite mammal species?

Well, no. The truth is, in many ways, even more fascinating. It turns out that all hyenas, male and female, are born with what appears to be a penis. The two genders are almost impossible to tell apart until they reach sexual maturity and they either have babies or don't. The apparent penis in females is an external birth canal. When the babies are born, they pass through the cervix internally, but then pass into this external canal, which is less muscular than a usual birth canal. But hyena babies are very robust and born with a full set of teeth. They work and squirm their way out of the birth canal on their own, and in some cases, where a particularly big baby wants out, they have been known to chew their way out of the birth canal. (Because it is an external organ, the mothers can survive this, usually with no real damage.) Once the cubs are born, the first thing they do is fight to the death, killing the smallest cub. Sometimes babies are born already dead and covered in teeth marks - apparently from being attacked and killed by their siblings in the womb. It's a brutal start to life, but an efficient one in that it ensures that the mother does not waste resources on raising a baby that will not survive to adulthood.

The presence of the apparent penis isn't the only typical male characteristic that female hyenas have. At the equivalent of hyena puberty, when male and female hormones come into play in mammal species, the female hyena begins to produce massive amounts of testosterone, the male hormone. She gets larger than the males and puts on more muscle mass, and becomes very aggressive. The males, on the other hand, produce less testosterone and become very submissive to the females. This structure remains in place throughout a hyena's life. Their social structure is strictly hierarchical, and matrilineal, with the alpha, or lead, position held by a female and passed down from mother to daughter. All females are dominant to all males in the hierarchy, e.g. the lowest-ranking female still outranks the highest ranking male. Males leave their birth clan at adulthood and join another clan, where they begin to work their way up the male hierarchy.

Clearly, hyenas are like no other animal on earth. No one has really figured out why they have evolved the traits that they have, and much of their behavior is still mysterious to us. Even our fear of them is somewhat mysterious - they are no more dangerous or dirty than any other predator, yet we humans have an almost visceral fear of them. Seeing one looming up at you out of the darkness, or hearing their strange cackling call, stirs something deep and primal and afraid in us. And it has always been such - even in myth and legend, the hyena is a figure of fear and deceit and cowardice.

Maybe it's because, no matter how much we try to tell ourselves that they are really fascinating animals with a role to play and a place in the world - they are still really, really smelly.