This story appears in the January 2016 issue of National Geographic magazine.

AT SUNSET THE WILDEBEEST SEEMS DOOMED: Sick or injured, it’s wandering miles from its herd on the Serengeti Plain of Tanzania. By sunrise the loner is dead, draped in a roiling scrum of vultures, 40 or so birds searching for a way to invade its earthly remains. Some of the scavengers wait patiently, with a Nixonian hunch, eyes on their prize. But most are engaged in gladiatorial battle. Talons straining, they rear and rake, joust and feint. One pounces atop another, then bronco rides its bucking and rearing victim. The crowd parts and surges in a black-and-brown wave of undulating necks, stabbing beaks, and thrashing wings. From overhead, a constant stream of new diners swoops in, heads low, bouncing and tumbling in their haste to join the mob.

View Images A Rüppell’s vulture lays claim to a dead zebra in Tanzania’s Serengeti National Park, while other Rüppell's and white-backed vultures ( Gyps africanus) move in for a piece of the action. More vultures will likely join the banquet. They can strip a carcass clean in minutes.

View Images Blood drips from a Rüppell’s vulture’s beak as it pauses mid-meal. The neck and head of Rüppell’s are sparsely feathered, the better to keep gore, guts, and fecal matter from clinging after a deep carcass dive.

Why the fuss over a carcass so large? Why the unseemly greed? Because the wildebeestis tough-skinned and wasn’t killed by carnivores, it lacks an opening wide enough for general admission. And so the boldest birds compete furiously for access. As the crowd cackles and caws, a white-backed vulture snakes its head deep into the wildebeest’s eye socket and hurriedly slurps, with grooved tongue, whatever it can before being ripped from its place at the table. Another white-backed tunnels into a nostril while a Rüppell’s vulture starts at the other end; it’s eight inches into the wildebeest’s anus before another bird wrenches it away, then slithers its own head, like an arm into an evening glove, up the intestinal tract. And so it goes—40 desperate birds at five golf-ball-size holes.

Eventually, two lappet-faced vultures make their move. These spectacular-looking animals stand more than a yard tall, with wingspans of nine feet. (In treetops, they make stick nests as big as king-size beds.) Their faces are pink, their bills large and deeply arched, and their powerful necks festooned with crepey roseate skin and a brown Tudor ruff. While one lappet hammers a hole in the wildebeest’s shoulder, the other excavates behind a sinus, in hopes of finding juicy botfly larvae. Sinews and skin snap. Now a white-backed rams its head down the wildebeest’s throat and yanks out an eight-inch length of trachea, ribbed like a vacuum hose. But before the vulture can enjoy it, the four-foot-tall marabou stork that’s been stiffly lurking snatches the windpipe away, tosses it once for perfect alignment, and swallows it whole. Thanks to the labors of the lappets, which favor sinew over muscle, the wildebeest is now wide open. Heads fling blood and mucus into the air; viscera drip from vulture bills; two birds play tug-of-war with a ten-foot rope of intestine coated in dirt and feces.

Mealtime Get the carrion’s-eye view of a vulture feeding frenzy captured by a camera hidden in a dead zebra’s rib cage.

As the wildebeest shrinks, the circle of sated birds lounging in the short grass expands. With bulging crops, the vultures settle their heads atop folded wings and slide their nictitating membranes shut. No more sound, no more fury. As placid as suburban ducks, they rest, at peace with the world.

THE VULTURE MAY be the most maligned bird on the planet, a living metaphor for greed and rapaciousness. Leviticus and Deuteronomy classify vultures as unclean, creatures to be held in abomination by the children of Israel. In his diary during the voyage of H.M.S. Beagle in 1835, Charles Darwin called the birds “disgusting,” with bald heads “formed to wallow in putridity.” Among their many adaptations to their feculent niche: the ability to vomit their entire stomach contents when threatened, the better to take quick flight.

View Images In the Serengeti a golden jackal takes umbrage at an immature white-backed vulture butting in on its meal of dead wildebeest. Earthbound carnivores such as jackals and hyenas have limited territories in which to find food. Aloft, vultures have a much better view of the daily menu: They can spot a carcass 20 miles away.

Revolting? Perhaps. But vultures are hardly without redeeming values. They don’t (often) kill other animals, they probably form monogamous pairs, and we know they share parental care of chicks, and loaf and bathe in large, congenial groups. Most important, they perform a crucial but massively underrated ecosystem service: the rapid cleanup, and recycling, of dead animals. By one estimate, vultures either residing in or commuting into the Serengeti ecosystem during the annual migration—when 1.3 million white-bearded wildebeests shuffle between Kenya and Tanzania—historically consumed more meat than all mammalian carnivores in the Serengeti combined. And they do it fast. A vulture can wolf more than two pounds of meat in a minute; a sizable crowd can strip a zebra—nose to tail—in 30 minutes. Without vultures, reeking carcasses would likely linger longer, insect populations would boom, and diseases would spread—to people, livestock, and other wild animals.

But this copacetic arrangement, shaped by the ages, is not immutable. In fact, in some key regions it’s in danger of collapse. Africa had already lost one of its eleven vulture species—the cinereous vulture—and now seven others are listed as either critically endangered or endangered. Some, like the lappet, are found predominantly in protected areas (which are themselves threatened), and other regional populations of the Egyptian and bearded vulture are nearly extinct. Vultures and other scavenging birds, says Darcy Ogada, assistant director of Africa programs at the Peregrine Fund, “are the most threatened avian functional group in the world.”

Eater of the Dead The only land-based vertebrates that can thrive solely on scavenging, vultures are crucial to ecosystem balance. Because they can quickly devour large amounts of flesh and their stomach acids neutralize pathogens, vultures may help limit the spread of bacteria and diseases such as anthrax and rabies. But their numbers have been plummeting worldwide, with several populations at risk of collapse. Suited for Scavenging Vultures’ bulk allows them to survive on body reserves between discoveries of carrion. Anatomical adaptations help them expend as little energy as possible when soaring on thermals over ranges—up to 185,000 square miles—in search of food. Rüppell’s vulture

Gyps rueppelli Crop Gizzard Intestines Primary feathers Secondaries Space between primary feathers reduces drag and lowers stalling speed while maintaining lift. Bald head Baldness in many vulture species is related to thermoregulation and hygiene. Head feathers would catch gore and viscera. Eyes Compared with raptors that hunt, vultures have less powerful eyesight but still excel at spotting carcasses and converging scavengers. Crop Some vultures can store up to 20 percent of their body weight in consumed flesh in this enlarged section of their esophagus. Gut Highly corrosive, bacteria-killing stomach acids give vultures a high tolerance to toxins in decaying flesh. Vulture Albatross Sailplane Wings Broad wings and long primary feathers, compared with other soaring birds, enable energy-efficient gliding on even the weakest air currents. Hooded

vulture White-backed

vulture Lappet-faced

vulture Beak Hooked bills help with ripping meat. Still, only the largest vultures can tear open a carcass, allowing smaller vultures to access innards. Ruppell's

vulture Turkey

vulture Nostrils Turkey and yellow-headed vulture species have a keen sense of smell, unique among birds, with nostrils not divided by a septum. Backward-facing

barbs Tongue Vultures have adaptations like deep grooves and backward-facing barbs for quickly gulping hefty portions of carrion. Turkey

vulture Ruppell's

vulture Golden

eagle Feet Vultures spend more time on the ground than other raptors, and have developed flatter feet and shorter, less curved claws. States of Decline There are 23 species of vulture divided into two families by hemisphere, New World and Old World, each facing threats. Number of species 1 8 None ASIA EUROPE NORTH AMERICA AFRICA SOUTH AMERICA AUSTRALIA Americas: Recovering When counts of California condors began in the early 1900s, the birds’ ranks had already been decimated.After decades of conservation efforts, numbers are growing, but lead poisoning from spent ammunition in scavenged carcasses is still a threat. California Condor Population 1950

150 wild condors 1967

1 captive 2012

235 2012

169 Africa: Declining Poisoned by herders aiming to protect their livestock and by poachers afraid that circling vultures will give away their location, some groups are shrinking by as much as 50 percent a decade. Traditional healers believe vulture brains grant the ability to see the future. Causes for Decline in African Vultures 1% Killing for food 9% Electrical infrastructure 29% Killing for traditional medicine 61% Posioning India: Crashed India’s populations plunged in the mid-1990s. Hindu belief prohibits consumption of beef, so cows that die are disposed of outdoors. Vultures died of kidney failure after eating cows that had been treated with the bovine drug diclofenac. The drug was banned in India in 2006. Birds Counted in Indian Transect Surveys 2000

vultures 0 2007 1992 -96.8%

Indian and Slender-billes -99.9%

White-rumped 23 Species of Vulture Critically endangered Endangered Near threatened Least concern MATTHEW TWOMBLY, LAUREN C. TIERNEY, CHIQUI ESTEBAN, NGM STAFF; MESA SCHUMACHER. ART: MATTIAS SNYGG

SOURCES: DARCY OGADA, PEREGRINE FUND; SIMON THOMSETT, NATIONAL MUSEUMS OF KENYA; STEVE KIRKLAND, U.S. FISH AND WILDLIFE SERVICE; BIRDLIFE INTERNATIONAL; VIBHU PRAKASH, JOURNAL OF THE BOMBAY NATURAL HISTORY SOCIETY, 2007

On a sunny March day Ogada is traveling with her colleague Munir Virani in the Masai Mara region of Kenya. Virani is here not to study his beloved birds but to speak with herdsmen about their cows. Livestock husbandry, it turns out, is essential to vulture welfare. As our truck weaves through flocks of sheep and goats, Virani explains how the Maasai have in recent years leased their land, which rings the northern section of the Masai Mara National Reserve, to conservancies established to protect wildlife by excluding pastoralists and their livestock. Some Maasai claim the conservancies have lured more lions and other carnivores to the area. (The conservancies are contiguous and unfenced.) Meanwhile populations of wildebeests and other resident ungulates in the Mara ecosystem are facing threats from poaching, prolonged drought, and conversion of savanna to cropland and real estate. This in itself would be bad news for vultures, but there’s worse.

Virani asks every Maasai we meet: Have you lost any livestock to predators recently? The answer is always, “Yes, and my neighbors have too.” Usually the lions attack at night, when the cattle are penned inside bomas—corrals ringed with thorny brush. The lions roar, then terrified cattle stampede, crash through the boma gate, and scatter. Dogs bark, waking their owners, but it’s usually too late. The killing of a single cow represents a loss of 30,000 shillings ($300), a significant blow to families that use livestock as currency (a bull can be worth 100,000 shillings).

Next comes retaliation: The men tie up their dogs, retrieve what’s left of the lion’s kill, and sprinkle it with a generic form of Furadan, a cheap, fast-acting pesticide that’s readily available under the table. The lion returns to feed, most likely with its family, and the entire pride succumbs. (Researchers estimate that Kenya loses a hundred lions a year in these conflicts. The country has roughly 1,600 lions left.) Inevitably vultures also visit the livestock carcass, or they eat the poisoned lions themselves. Whatever the vector, the birds, which can feed in “wakes” of more than a hundred individuals, all die as well.

It’s hard to believe that just a few granules of a compound designed to kill worms and other invertebrates can lay low an animal whose gastric juices are acidic enough to neutralize rabies, cholera, and anthrax. Indeed, Furadan was scarcely on Ogada’s radar until 2007, when she began receiving emails from colleagues about poisoned lions. “That raised some eyebrows,” she says. Tourism is Kenya’s second largest source of foreign income, and lions are the nation’s star attraction. In 2008 scientists and representatives from conservation groups and government agencies convened in Nairobi to share information on poisonings and plan a response. “Jaws dropped,” Ogada remembers. “The problem was far larger than any of us, working locally, knew.” Once Ogada and others began to study the problem, they estimated that poisoning accounts for 61 percent of vulture deaths, Africa-wide. The anthropogenic threat is compounded by vultures’ reproductive biology: They don’t reach sexual maturity until five to seven years of age, they produce a chick only once every year or two, and 90 percent of their young die in the first year. Over the next half century vulture numbers on the continent are projected to decline by 70 to 97 percent.

AS BAD AS THE AFRICAN SITUATION appears, it has been worse elsewhere. In India populations of the most common vultures—white-rumped, long-billed, and slender-billed—declined by more than 96 percent in just a single decade. Then in 2003 researchers from the Peregrine Fund definitively linked bird carcasses with cattle that had been treated with an anti-inflammatory called diclofenac. Initially prescribed for arthritis and other pain in humans, the drug had been approved for veterinary use in 1993. In vultures, diclofenac causes kidney failure: Autopsies reveal organs coated with white crystals.

The Indian die-off received a lot of attention because its downstream effects were so startling. India has one of the largest cattle populations in the world, but most Indians don’t eat beef. After millions of vultures fell victim to poisoning, dead cattle started piling up. Then the dog population—released from competing with vultures for scavenged food—leaped by 7 million, to 29 million animals over an 11-year period. The result: an estimated 38.5 million additional dog bites. Rat populations soared. Deaths from rabies increased by nearly 50,000, which cost Indian society roughly $34 billion in mortality, treatment expenses, and lost wages. India’s Parsi community in Mumbai was alarmed to note another change. The corpses they ritually place on elevated stone platforms for “sky burial”—in which vultures liberate the souls of the dead so that they can reach heaven—were taking months longer to disappear, because there were no vultures left to feed on them.

View Images Conservationists in Namibia use a car side-door mirror on a pole to peek into a lappet-faced vulture’s nest in a tree. If they find a chick that’s old enough, they’ll retrieve it, wing tag it, and put it back. Females may lay only one egg every year or two, so every chick’s survival is critical to the population’s future.

After researchers proved that diclofenac was to blame for the vulture die-off, in 2006veterinary use of the drug was banned in India, Pakistan, and Nepal. (It’s still given to cattle clandestinely.) Bangladesh followed suit in 2010, and in mid-June 2015, a coalition of conservation groups urged the European Commission to ban the drug’s use in animals. A response is pending. In combination with captive-breeding programs andvulture “restaurants,” which serve safe meat from farms or abattoirs to wild birds, the campaign has done some good. Nine years on, Indian vulture declines have slowed, and in some regions their numbers have even begun to increase. But the population of the three hardest-hit species remains a small fraction of its former millions.

OGADA ISN’T HOPEFUL that Africa will follow India’s lead in responding to the vulture crisis. “There has been little government action to conserve vultures in Kenya,” she says, “and no political will to limit the use of carbofurans,” the chemical family that includes Furadan. And although vultures in India face just one major threat—unintentional poisoning—vultures in Africa face many more.

In July 2012, 191 vultures died after feasting on an elephant that had been poached and then sprinkled with poison in a Zimbabwean national park. A year later roughly 500 vultures were killed after feeding on a poison-laced elephant in Namibia. Why do poachers, intent on ivory, target vultures in this way? “Because their kettling in the sky over dead elephants and rhinoceroses alerts game wardens to their activities,” Ogada says. Ivory poachers now account for one-third of all East African vulture poisonings.

Cultural practices have also taken a toll on vultures. According to André Botha, co-chair of the vulture specialist group at the Inter­national Union for Conservation of Nature, many of the birds found at poached carcasses are missing their heads and feet—a sure sign they’ve been sold for muti, or traditional healing. Shoppers at southern African markets have little trouble buying body parts believed to cure a range of ailments or impart strength, speed, and endurance. Dried vul­ture brain is also popular: Mixed with mud and smoked, it’s said to conjure guidance from beyond.

View Images A vendor in Durban, South Africa, proffers vulture heads for sale as muti—traditional medicine. Dried and smoked, vulture brains are also thought to provide visions of the future. The birds’ own prospects are bleak. Six of eight species in the country are endangered.

Still, the biggest existential threat to African vultures remains the ubiquitous availability and use of poisons. FMC, the Philadelphia-based maker of Furadan, began buying back the compound from distribution channels in Kenya, Uganda, and Tanzania—and suspended sales in South Africa—following a 60 Minutes segment on lion poisonings in 2009. But the compound, in generic form, persists. Agriculture is the second largest industry in Kenya, and the nation has a long history of using toxins to combat outbreaks of disease and pests. Anyone can walk into a Kenyan agro-veterinary shop and, for less than two dollars, buy highly toxic pesticides off the shelf—to kill insects, mice, feral dogs, hyenas, leopards, jackals, and even fish and ducks meant for human consumption. (Poachers claim, erroneously, that removing the animal’s entrails, then slowly roasting the carcass, detoxifies the flesh.)

“You cannot have agriculture in the tropics without pesticides,” Charles Musyoki, former head of species management for the Kenya Wildlife Service, says. “So we need to educate the public about their correct and safe use.”

What the public understands now is that carbofurans are cheap, reliable, and—compared with stalking and spearing a predator—risk free. To date, the government hasn’t prosecuted a single poisoner of vultures. “Poisoning predators is just part of the culture,” Ogada says with a shrug. Indigenous groups have always protected their herds, and the descendants of Europeans—who introduced cheap synthetic poisons in the first place—have been slaughtering mammalian and avian carnivores in Africa for more than 300 years.

AFTER A LONG DAY of speaking with Maasai herdsmen, Virani and Ogada are eager for the sun to set, not to escape the heat but to witness the flicking of an electrical switch. In the gloaming, Virani parks his jeep outside a compound that sits in the pounded dust bowl between the 50,000-acre Mara Naboisho Conservancy, to the east, and the 400,000-acre Masai Mara reserve, to the west. Under a velvet sky glimmering with stars, Virani stares at a boma and, when a dozen lightbulbs strung between fence posts blink on, breaks into a grin.

Balloon safari operators, who ascend before daybreak, have complained about this nighttime light pollution. But to Virani these flashing bulbs, connected to a solar battery, are a minor miracle, the safest, most cost-effective way to keep predators away from cattle pens and short-circuit the retalia­tory poisoning that’s decimating vultures.

“The lights cost between 25,000 and 35,000 shillings per boma,” Virani says—between $250 and $350, with the Peregrine Fund picking up half of that. “Prevent one cattle predation, and they’ve paid for themselves.” In their first six months of deployment in this part of the Mara, lion attacks on 40 bomas with arrays went down by 90 percent. So far, carnivores and elephants—which commute between the conservancies and the reserve, often through Maasai vegetable patches—are still avoiding the lights, but lack of maintenance and mismanagement of the systems (siphoning power to charge phones, for example) have reduced their effectiveness. Still, demand for the arrays far outpaces supply.

ON THE SERENGETI, about 150 miles to the south of the Masai Mara, the sun rises on three adult hyenas, shoulder deep in yet another dead wildebeest. Now and then the feathered audience that has gathered at this theater-in-the-round advances toward the stage, only to be rebuffed by the principal actors raising their chins and curling their black lips. The vultures take the hint. There is, between the four-legged and the two-, a palpable respect: Hyenas rely on vultures to locate kills, and vultures rely on hyenas to quickly bust them open.

Eventually the hyenas are full enough to retreat, cuing the birds to swarm. Now the carcass rocks back and forth as two dozen vultures rip, slurp, pry, and tug. Suddenly a lappet drops out of the sky, then bashes skulls with two other lappets standing innocently on the periphery. The aggressor wheels, ducks its head, raises its massive wings, then mounts the wildebeest in triumph. “They are the most amusing animals,” Simon Thomsett, a vulture expert affiliated with the National Museums of Kenya, says, binoculars to his eyes. “You certainly couldn’t spend this long watching a lion.”

Hours pass, the bloody players come and go: hyenas, jackals, storks, scavenging eagles, and four species of vulture. Despite the apparent hysteria, everyone gets a chance, partitioning the carcass in time and space according to social status and physical ability.

View Images Sprinkled on carrion, a few ounces of the insecticide carbofuran (above) can kill a hundred vultures. Poisoned birds that are caught quickly or haven’t consumed too much may be saved if given a dose of the drug atropine and fed charcoal, which absorbs the poison.

Both Thomsett and Ogada, who often collaborate, have spent much time pondering what would happen if vultures were subtracted from this cast of characters. Running field experiments with goat carcasses over a two-year period, Ogada learned that in the absence of vultures, carcasses took nearly three times as long to decompose, the number of mammals visiting carcasses tripled, and the amount of time these animals stayed at the carcass also nearly tripled.

Why do these data matter? Because the longer jackals, leopards, lions, hyenas, genets, mongooses, and dogs commune with one another at a carcass, the more likely they are to spread pathogens—which die in vulture stomachs—to other animals, both wild and domesticated. By eating wildebeest placenta, Thomsett tells me from his perch in the jeep, vultures also prevent cattle from contracting malignant catarrh, an often fatal herpes virus. And by reducing carcasses to bones within hours, they suppress insect populations, linked with eye diseases in both people and livestock.

“Vultures are more important, in terms of services to humanity, than the ‘big five’ that everyone comes here to see,” he says. Their loss, scientists believe, would likely set off an ecological and economic catastrophe.

View Images A white-backed vulture recovers at the VulPro facility after being poisoned with carbofuran. The bird was later released.

Although poisoning is the proximate driver of Africa’s vulture decline, the plain-speaking Thomsett stresses its root cause: too many people. Kenya’s population is expected to reach 81 million, from today’s 44 million, by 2050. And the Maasai are among the fastest growing groups in the country.

Thomsett lowers his binoculars and expands on the list of anthropogenic threats to Kenya’s vultures. Farmers are planting corn and wheat around protected areas to feed the growing population, he says. Less grassland means fewer ungulates for vultures to eat. The government hasn’t been able to stop drilling for geothermal wells within 300 meters (328 yards) of endangered Rüppell’s nesting sites, he continues. Vultures are also killed in collisions with high-tension power lines. The Kenya Wildlife Service has yet to write, let alone implement, a strategic plan for vulnerable vulture species. (Such a plan is imminent, the service’s Charles Musyoki told me.)

In December 2013 Kenya passed an act that imposes a fine of up to 20 million shillings ($200,000) or life imprisonment on anyone linked with killing an endangered species. And the Kenya Wildlife Service is said to be planning a campaign to shift the public’s perception of vultures. But without better investigating and enforcement of anti-poisoning laws, to say nothing of convicting perpetrators, Ogada and Thomsett agree, such campaigns won’t be nearly enough to save the region’s birds. More immediately effective, they say, would be for the government to accept an offer from a landowner in southwestern Kenya. He has offered to sell land containing one of the nation’s most important breeding cliffs for the critically endangered Rüppell’s vulture.

Thomsett continues to observe the vultures wallowing in putridity, making detailed sketches of their heads and feet in a thick notebook, until the birds have eaten their fill and the wildebeest resembles a wrinkled blue-gray rug, with hooves. In the days to come, any remaining scraps of skin and sinew will be ravaged by the elements, by insects, fungi, and microbes. The ungulate’s larger bones will persist for years, but in the meantime its basic building blocks will cycle on—in the soil, in vegetation, and in every glorious vulture that fed on its prodigal abundance today.