The most obvious advantage of "these bizarre structures," as Holekamp calls them, is power over reproduction. Mating is impossible without full female cooperation. And if a female changes her mind about a male after mating, the elongated reproductive tract lets her flush out the sperm by urinating.
Holekamp has developed a new theory to explain the evolution of the hyenas' female-dominated social structure and odd reproductive apparatus. "I think the bone-crushing adaptation is the key to it all." She explains: spotted hyenas' ancestors evolved massive skulls, jaws and teeth so they could pulverize and digest bones. This gave them a tremendous advantage over other predators, but with a cost: the skull and jaws that make bone-crushing possible take several years to mature. Holekamp has found that young hyenas can barely crunch dog biscuits. Hyena mothers care for their cubs for three or four years, much longer than most other predators do. Alone, cubs would be unable to compete for food at kills. "That put pressure on females to give their kids more time at the carcass," says Holekamp. Females had to become bigger and meaner, Holekamp hypothesizes, which they achieved partly by boosting their "masculinized" hormones. If Holekamp is right, female dominance and matriarchy among spotted hyenas stem from evolutionary adaptations made for the sake of feeding the kids.
One dawn we spot a hyena named Cashew. She is 4, old enough to collar, so Cokayne prepares a tranquilizer dart, aims for the haunch and fires. Cashew leaps sideways, bites the dart, spits it out, sniffs it, flinches, sniffs again. Then, seemingly unfazed, she resumes her steady pace and disappears into the tall grass.
Cokayne gets out of the Land Cruiser to look for Cashew as Holekamp drives slowly ahead. A few yards into the tall grass Cokayne finds the animal conked out. Holekamp takes several vials of blood from Cashew's long, muscular neck, then measures the skull, tail and teeth. She is three feet long, 112 pounds, a petite strawberry blonde with coarse fur and tan spots. Her big black nose and feet are doglike. Her dark brown nipples are growing; she might be pregnant for the first time. (For an earlier study, Holekamp and her colleagues used portable ultrasound equipment to determine how many fetuses were carried by female hyenas.) Cokayne scrapes some beige paste from a gland near the anus; hyenas rub this musky substance onto grass, stones and trees to mark their territory. Holekamp has witnessed clan wars near territorial borders. Females lead the attack.
Holekamp and Cokayne fit Cashew with a radio collar and an ear tag. The hyena unexpectedly lifts her head and drills her huge dark eyes into us. I suddenly feel like a slow topi, but the scientists are relieved that the tranquilizer is wearing off. Nearly 20 years ago, when a darted hyena stopped breathing, Holekamp resuscitated it, mouth to mouth. Her report on hyena breath: "Not too good."
Holekamp and Cokayne take Cashew to a shady gully where she can recover unseen by lions, which go out of their way to kill hyenas. The lions' motive isn't clear, but it's not hunger; they won't eat a hyena. Goodall writes about being shocked by "the viciousness, the seeming hatred," of a lion who attacked one. Holekamp traces 60 percent of the mortalities among her hyenas to lions. One pre-dawn we came across half a dozen lionesses lounging near a male with a crescent scar under his eye. "That's Adrian," said Cokayne. "I'd know him anywhere. He's a murderer." A month earlier she had been watching a hyena resting ten feet from her vehicle. "Adrian came out of the tall grass, took three giant leaps, and got the hyena by the throat and strangled it," says Cokayne. Two weeks later, a lion killed a hyena named Leonardo. The hyena's skull was now at Fisi Camp in a metal pan hanging from a tree, getting picked clean by beetles before joining Holekamp's specimen collection.
Holekamp says she keeps studying hyenas because they keep surprising her. Lately she has become intrigued by their intelligence. Hyenas are proving to be very smart—in some ways, as smart as primates, according to Holekamp's research. They live in societies as complex as those of some primates and seem to show as much social intelligence. Also like primates, they form coalitions and understand that certain relationships are more valuable than others. Like primates, they learn and follow rules of social status and behavior, and they solve social problems in ingenious ways, using distraction, deception or conciliation. Holekamp has seen lower-ranked animals give an alarm cry during a feeding frenzy to make others flee so there's space at the carcass. Benson-Amram has seen hyenas use the same tactic to scare away higher-ranking animals who were bullying a cub.
Benson-Amram has been devising hyena I.Q. tests. For instance, she puts meat into a small steel cage with a latch, then times how long a hyena takes to figure out how to open it. One subadult quickly solved the puzzle, and now every time Benson-Amram shows up with the cage, the animal—which she nicknamed Einstein—trots over and quickly unlatches the box lunch. Holekamp says, "Just how smart are they?" The researchers are still trying to find the limits of hyena intelligence.
Science's version of the spotted hyena—smart, matriarchal, obsessed with status, biologically and socially complex, jam-packed with surprises—has not displaced the repulsive cowardly scavenger of popular imagination. Holekamp has noticed that safari van drivers in Masai Mara assume that tourists dislike hyenas and rarely take them to dens. "If they did, I think people would be fascinated," she says, "because the animals are so weird."
Steve Kemper, a frequent contributor, wrote about mountain lions in the West for the September 2006 issue of Smithsonian.