Nor do things improve much when it comes to mating. "With most animals, males duke it out and the winner gets the girls," says Holekamp. "But with hyenas, females have 100 percent say." They decide when and under what conditions they will tolerate deferential sperm donors. At age 2 or 3 a male leaves his natal clan and wanders off to beg acceptance into another clan. After vicious rejections, he eventually succeeds and reaps his reward: brutal harassment as the clan's nadir, one of the last in line for food and sex. This probation, which biologists call "endurance rivalry," is a test, Holekamp explains: "The guy who can stick it out the longest wins." The trial lasts about two years, after which some females may grant him access. "You do not want to be a male hyena," Holekamp says.
An hour before dawn, we are bouncing along a track in Masai Mara. Topi antelopes stand quietly in the dark, Thomson's gazelles dash away and a giraffe's silhouette brushes the fading stars. Hyenas usually rest during the hot daylight hours, so Holekamp and her researchers typically work a split shift in the field, mornings from 5 to 9, evenings from 4 to 8.
The Land Cruiser's transmitter beeps, indicating a radio-collared hyena nearby. It's Murphy, alpha female of a clan that Holekamp calls Talek West. (Murphy's half-sister, Whoopie, rules Talek East.) Each clan comprises about 50 animals. They had once been united under their mother, Bracket Shoulder, who had been in power for a decade when Holekamp first came to Masai Mara. Thus Bracket Shoulder and her daughters have ruled the Talek group for 30 years.
The clan split into east and west factions in the late 1990s when herders from the Masai tribe began illegally grazing their cows in the middle of the clan's territory. Grazing has worsened as growing numbers of people and livestock press against the reserve, home to 400 to 450 adult spotted hyenas. The Masai, like herders and ranchers throughout Africa, consider hyenas livestock-killing vermin. They often stab, snare or poison them. Nevertheless, spotted hyenas are the most numerous large predator in Africa.
The Masai have largely escaped the violence that has racked Kenya since disputed elections in December. Before a power-sharing agreement was reached in March, more than 1,000 people were killed and 500,000 or more were displaced. In Masai Mara, the upheavals have led to more poaching, fewer tourists and less money for conservation, but the hyenas that Holekamp's group studies haven't been harmed.
"Most hyenas die violently, from lions or people," says Holekamp, "but Bracket Shoulder died at 17 of kidney failure. And she was still in power." She still had perfect teeth, too, since her rank assured her the best cuts of meat, whereas the teeth of lower-ranking animals get chipped and worn from crunching bones.
As sunrise suffuses the sky, we pass through a section of tall grass, the boundary with the neighboring Fig Tree clan. Three hyenas appear in the fresh light, their bellies distended, heads and chests bloody. One carries what's left of the kill, a topi's skullcap, recognizable by its tall ridged horns. Hyenas peel the horns' keratin coating and eat the bones beneath.
Spotted hyenas in Masai Mara subsist mostly on topis and Thomson's gazelles until the great herds of wildebeest migrate through from the Serengeti. Holekamp thinks hyenas' favorite food is fresh zebra—she's seen them bypass easier prey in hopes of a striped entree—but they will eat anything with fur, feathers, wings or scales. Holekamp was once puzzled by a group of hyenas that seemed to be grazing; they were licking a bloom of caterpillars off the grass. After a rain, when termites shoot out of their mounds like fountains, hyenas stand over the holes and guzzle.
To a hyena, almost anything organic is edible. Aimee Cokayne, a research assistant who's been living at Fisi Camp for much of the past 20 months, remembers a hippo that died in a mudhole. Hyenas tore chunks from the rotting carcass for months, unfazed by the increasing putrefaction. Holekamp says that if Masai boys flip a large tortoise onto its back as a prank and it decays into a tureen of carrion soup, hyenas lap it up. (They also roll in it.) They even snack on the dung of wild dogs and wildebeests. Is anything putrid enough to gag a hyena? Holekamp thinks hard. "No," she finally says. "I haven't seen that yet."
She is collaborating with a microbiologist at Michigan State to study hyenas' hardy immune systems. Other species suffer pandemics (rabies in wild dogs, distemper in lions, anthrax in ungulates), but hyenas appear to be unscathed by disease, not to mention rotten meat. "How do they tolerate foods that most creatures find deadly?" Holekamp is still trying to figure that one out.