Monday, May 23, 2005

Crocuta crocuta: Part 2

"Even the grass..."

If the spotted hyena had a signature phrase, it might well be the same of that as the late comedian, Rodney Dangerfield: "I can't get no respect." Long characterized as craven and stupid, the species is considered a villainous thief, a money-for-nothing scavenger that creeps onto the scene only after the real work has been done. In Disney's "The Lion King," the hyenas are slobbering, giggling fools. Likewise, in many a dated nature documentary the lowly hyenas are most often seen being run off by the "proud and noble lions."

Much of this disrespect is a result of our human aesthetic preferences. Rarely do I ask someone to describe a hyena and not hear the words "ugly," "disgusting," or "dirty." Yann Martel, in his terrific novel, Life of Pi, gives the reader a fair assessment of spotted hyena behavior, but the animal is still described as "ugly beyond redemption."
"Its thick neck and high shoulders that slope to the hindquarters look as if they've come from a discarded prototype for the giraffe, and its shaggy, coarse coat seems to have been patched together from the leftovers of creation. The colour is a bungled mix of tan, black, yellow, grey, with the spots having none of the classy ostentation of a leopard's rosettes; they look rather like the symptoms of a skin disease, a virulent form of mange. The head is broad and too massive, with a high forehead, like that of a bear, but suffering from a receding hairline, and with ears that look ridiculously mouse-like, large and round, when they haven't been torn off in battle. The mouth is forever open and panting. The nostrils are too big. The tail is scraggly and unwagging. The gait is shambling. All the parts put together look doglike, but like no dog anyone would want as a pet."
So what is this strange animal? Why does it seem to be "patched together from the leftovers of creation" and what is it actually like? Dogs, bears, raccoons, weasels, and badgers are all members of sub-order Caniformia. The physical appearance and greeting behaviors of the Hyaenidae family - four species: spotted hyena (Crocuta crocuta), striped hyena (Hyaena hyaena), brown hyena (Hyaena brunnea), and aardwolf (Proteles cristata) - lead many to assume that they belong to Caniformia as well. In fact, hyenas are more closely related to the house cat sleeping on the ground next to me; they are members of sub-order Feliformia. Of the four living hyena species, the aardwolf and spotted hyena represent the more ancient lineages, the spotted hyena being the sole survivor of a "diverse, very successful and advanced carnivore/scavenger that ranged from Europe to Indonesia."(1) The other members of the Crocuta genus were much larger animals, some of them bear-size, and the smaller build of the spotted hyena enabled them to persevere while larger relatives perished. Excepting the aardwolf, hyenas have incredibly tough digestive systems, capable of digesting mammal bones in a few hours and teeth in a few days. They have even been known to consume and digest semi-poisonous compounds with no observed ill effects. Considering the bone crushing strength of the hyena jaw and the speed with which they consume food, such an adaptation is rather vital. As Martel writes, "It is not their gastric juices that limit hyenas, but the power of their jaws, which is formidable."

I am fascinated by all of the hyena species, but I find the spotted hyena most curious by far. The complex social architecture of a spotted hyena clan is notably different from that of its closest relatives. The striped hyena, for example, is a relatively solitary animal. Adults do not tolerate members of the same sex, so males and females come together to mate and raise offspring but spend much their time alone. The brown hyena typically shares a home range with only a small number of close relatives. The spotted hyena, however, can live in clans of up to 100 animals (in some cases, where food is plentiful, the clans can even exceed this number, though an 80 adult clan is extremely rare). Understandably, such large groups require some degree of socialization. Until recently, however, the sophisticated social dynamics of spotted hyenas remained unknown.

Inherited social status - an animal born of a high-ranking parent is automatically considered superior to those from a lesser lineage - is uncommon among group-living mammals. Usually size, strength, and other physical abilities determine rank. A weak or timid elk (Cervus elaphus), or wapiti, is unlikely to build a harem and be a good breeder, just as a smaller, less offensive grey wolf (Canis lupis) will be subservient to the more aggressive, powerful males. Primates were long believed to be the only exception to the rule, but biologists have learned that spotted hyenas also break the mold. Crocuta crocuta lives in large matriarchal clans with a rigid hierarchy. Rank passes directly from a mother to her cubs. Oddly, a male cub, no matter how highly ranked his mother is, will eventually leave his clan (at between 2 and 5 years of age). By contrast, all females remain with their "birth clan." The lone male spotted hyena faces a hard life and must hope for acceptance into a new clan. Should he be accepted, he will start at the absolute bottom of the hierarchy. Ranking even lower than the lowliest of cubs, he must greet them with a submissive posture. Reduced in this way, the immigrant male will also be forced to feed last. If the clan he has joined is large, feeding last can sometimes mean gnawing on bones or surviving on the feces of your clan mates.

Zoologist Kay Holekamp, of Michigan State University, studies the spotted hyena in Kenya. Holekamp wondered why males would choose to leave their clan and suffer such a fate. The answer she found is surprising. Holekamp discovered that immigrant males father an astounding 97 percent of cubs, "even though they are outranked by younger native males." Curiously, the tenure of an immigrant male is significant. A newly arrived immigrant is unlikely to find receptive females, but those that have been with the clan for some time will have sex offered more often, despite the fact that they remain at the bottom of the pecking order. This arrangement makes good genetic sense (limiting inbreeding), but some readers may wonder why the males are so willing to play by the matriarchal society's rules, why they don't "take" the females as is common in so many other mammalian species?

The answer, as with most things Crocuta crocuta, is very unusual. Not only are the females the dominant sex, they are also physically larger (on average, 12% heavier) and more aggressive than the males.
"This female dominance comes by way of a rare degree of masculinization. Female hyenas...have higher concentrations of the typically male hormone androstenedione in early life and are host to some bizarre genital morphology. The hyena clitoris is an elongated structure that resembles the male's penis. The females urinate, mate, and give birth through this highly elastic pseudopenis."(2)
Because of this peculiar morphology, female hyenas are in complete control of the sex act. In order for the male hyena to mate successfully, the female must retract the clitoris inside of her, as if inverting a sock, allowing the male to insert his smaller penis. Also of note, the birthing process is incredibly difficult on female hyenas. Imagine a human female giving birth through an enlarged clitoris, and you begin to get a sense of the excruciating pain the mother hyenas experience when giving birth, especially the first time! Biologist Laurence Frank (University of California, Berkeley) says of the spotted hyena birthing experience, "It's the only time I've ever heard hyenas cry out in pain."(3) In fact, many first-time mothers die after giving birth.

There have been many fine articles on Crocuta crocuta in the last decade (the two quoted articles are good places to start) and what I have written above should serve as a springboard. If you have any questions about the species, feel free to ask. Odds are I know the answer and, if I don't, I'm sure I'll have fun finding out.

I'll close with another selection from Life of Pi.
"These were not cowardly carrion-eaters...Hyenas attack in packs whatever animal can be run down, its flanks opened while still in full motion. They go for zebras, gnus and water buffaloes, and not only the old or the infirm in a herd - full-grown members too. They are hardy attackers, rising up from buttings and kickings immediately, never giving up for simple lack of will. And they are clever; anything that can be distracted from its mother is good. The ten-minute-old gnu is a favourite dish, but hyenas also eat young lions and young rhinoceros. They are diligent when their efforts are rewarded...Nothing goes to waste; even the grass upon which blood has been spilt will be eaten."
(1) The Kingdon Field Guide To African Mammals. Jonathan Kingdon, Academic Press, 1997
(2) "Rebranding the Hyena," John Pickrell, Science News, April 27, 2002
(3) "Sex and the Spotted Hyena," Robin Meadows, Smithsonian ZooGoer 24(3), 1995

Photo credit: The Lion King, Walt Disney Pictures


Devo said...

HOly cow... you're right, HH, I've never known anywhere near this much about hyaenas. Thanks for once again edifying me.

Also, between this post and the story from Africa, it seems to me that of all the wild animals I might encounter, I should probably be most wary of a crew of Hyaenas... that's certainly different from anything I've ever learned from Walt and friends...

Anonymous said...

Thanks for bringing me up to speed HH. Excellent post. The hyaena "birthing experience" is news and painful to think about. A whole new meaning to ouch! Like their life isn't tough enough. And can you imagine the stress level of low-ranking newly immigrant young males.

Lené Gary said...

Great essay. I enjoyed the way you weaved science and literature together. I had never given much consideration to hyenas one way or another. Thanks for opening my eyes.

Anonymous said...

I'm curious if there is any theory as to what sort of selective pressure might have led to the hyaena's unique (?) morphology and sexual dimorphism. Perhaps this is already known, but if not I assume that theories have been floated.

Hungry Hyaena said...


Actually the bizarre genital morphology of the spotted hyaena is not unique, though it is the most extreme example biologists have found to date. Other examples I have read of include the elongated clitoris of both the female spider monkey (Ateles sp.) and European mole (Talpa europaea), but perhaps the most curious parallel will turn out to be the foosa (Cryptoprocta ferox), a distant relative of the hyaena and fierce predator that lives only on Madagascar. Unfortunately, it appears that foosa morphology changes with age. What often begins as a large clitoris becomes one of "normal" size by adulthood. Given their relative genetic similarity, I think more work could be done in this department.

More importantly, none of these other mammals use the clitoris in the same way. It certainly doesn't function as the birthing canal and it is rarely used, if ever, to showcase dominance or submission. Female spotted hyaenas use their clitoris as a sexual signalling device in much the same way male humans use their penis (at least in evolutionary terms; only a few friends still take out their wares at a cocktail party these days). (I agree with Jared Diamond's argument that, while a large penis may impress some ladies, our male sexual organs are principally meant for viewing by other men, testaments to our virility and strength. When a New Guinea man carves a penis gourd, he usually takes care to make it quite long and impressive. The poor soul who makes his to size, no matter how well-endowed he may be, is likely to be derided cruelly.)

As for the selective pressures which led to this morphology, most biolgists are stumped. Spotted hyaena researchers do surmise that the demand for aggression - such behavior earns more food and power - led to increased masculinization of the females, but this "solution" is really of little merit. If this were true, why do not all pack-living predators have dominant females and similar genitals? The morphology probably dates back to early hyaenas of the Crocuta genus, though I have not read of any fossils which prove as much.

So, the short answer is no one knows. Pretty crazy, huh?

Devo said...

Ha! "If I'd a known it was gonna be THAT kinda party, I'd a stuck my d!ck in the mashed potatoes!" That line rung like a bell in my head on your mention of wares at a cocktail party.

Funny name to choose for an example of places men generally don't whip it out, no?

Anonymous said...

Yo Reiger,
You should tell folks about elegant body design of the Hyena. Correct me if i'm wrong, but the high shoulder/ low hip combo coupled with massive jaws allow them to bite, hold, and dig in. Like an anchor with teeth, they immobilize larger prey until another Hyena can get a hold... until the prey is brought down.
That's what I learned anyways.

Anonymous said...

I saw a special on one of those discovery channels years ago called "Hyaneas: Nature's Gangsters". It was intense watching them hunt. I think they are awesome. And I'm jealous they have the strongest jaws in the world.

Anonymous said...

Thank you for your two part essays on the hyena. Like you I first fell for the spotted hyena,impressed by their complex social structure and the near constant animosity between lions and spotted hyenas (especially that both species will kill but not eat each other). This love was reinforced when I spent time with Mara, Seattle's Woodland Park Zoo's hyena. Her power and intensity was overwhelming.

Lately, most of my time has been spent with the striped hyena and I'd like to speak up for these little known members of the hyaenidae family. Smaller and shaggier, with huge bat-like ears, the striped hyena doesn't come charging up like the spotted. They hang back, watching and accessing and once they are comfortable, they will come over for a closer look. There is a quiet intellegence to them that is more dog-like than the spotted hyena - a gentleness that has been seen between family members that is lacking in spotted hyena society.

Yet they are still hyenas, capable protecting carcasses from leopards and occasionally tigers and with the same bone chilling laughing howl. I'd never heard anything as loud and frightening as the maniacal screaming, howling laughing voice of a striped hyena.