字幕表 動画を再生する 英語字幕をプリント In the grasslands of Mauritania, a gazelle suffering from tuberculosis takes its last breath. Collapsing near a small pool, the animal’s corpse threatens to infect the water. But for the desert’s cleanup crew, this body isn’t a problem; it’s a feast. Weighing up to 10 kilograms and possessing a wingspan of nearly 3 meters, the lappet-faced vulture is the undisputed king of the carcass. This bird’s powerful beak and strong neck easily tear through tough hide and muscle tissue, opening entry points for weaker vultures to dig in. This colossal competition is too dangerous for the tiny Egyptian vulture. With a wingspan of only 180 centimeters, this vulture migrated to Africa from his family nest in Portugal, using thermal updrafts to stay aloft for hours at a time. But upon arrival, he finds himself near the bottom of the pecking order. Fortunately, what he lacks in size, he makes up for in intelligence. A short distance away, he spots an unguarded ostrich nest, full of immense, but impenetrable eggs. Using a large rock, he smashes one open for a well-earned meal— though he’ll circle back to the gazelle once the larger birds are gone. High above the commotion are Ruppell’s Griffon vultures. Soaring at an altitude of over 11,000 meters, these birds fly higher than any other animal. At this height, they can’t see individual carcasses. But the sight of their fellow vultures guides them to the feeding. Their featherless heads help them regulate the sudden rise in temperature as they descend— and keep them clean as they tear into the decaying gazelle. The carcass is stripped clean in hours, well before the rotting meat infects the water supply. And the tuberculosis doesn’t stand a chance at infecting the vultures. These birds have evolved the lowest gastric pH in the animal kingdom, allowing them to digest diseased carrion and waste without becoming sick. In fact, species like the mountain-dwelling bearded vulture have stomachs so acidic, they can digest most bones in just 24 hours. This adaptation helps smaller vultures supplement their diet with dung, while larger vultures can consume diseased meat up to 3 days old. Their acidic stomachs protect them from living animals too: their rancid vomit scares off most predators. These stomachs of steel are essential to removing pathogens like cholera, anthrax, and rabies from the African ecosystem. But while vultures can easily digest natural waste, man-made chemicals are another story. Diclofenac, a common veterinary drug used to treat cattle in India, is fatal to vultures. And because local religious beliefs prohibit eating beef, scavengers often consume cattle carcasses. Since the 1990s, the drug, along with threats from electricity pylons and habitat loss, has contributed to a 95% decline in the region’s vulture population. In nearby Africa, poachers intentionally poison carcasses to prevent the birds’ presence from alerting authorities to their location. One poisoned carcass can kill over 500 vultures. Today, more than 50% of all vulture species are endangered. In regions where vultures have gone extinct, corpses take three times longer to decay. These carcasses contaminate drinking water, while feral dogs and rats carry the diseases into human communities. The Asian and African Vulture Crisis has led to an epidemic of rabies in India, where infections kill roughly 20,000 people each year. Fortunately, some communities have already realized how important vultures are. Conservationists have successfully banned drugs like Diclofenac, while other researchers are working to repopulate vulture communities through breeding programs. Some regions have even opened vulture restaurants where farmers safely dispose of drug-free livestock. With help, vultures will be able to continue their role conserving the health of our planet— transforming death and decay into life.