Mystery Disease Stalking Vultures in Asia

May 20, 2003

This week in Budapest, Hungary, an international gathering of scientists will explore how to save a creature that itself symbolizes doom: the vulture.

At the 6th World Conference on Birds of Prey and Owls, several sessions will focus on the Oriental white-backed vulture, Gyps bengalensis, once the most common bird of prey in Asia and possibly in the world.

Vultures used to be as numerous as "pigeons in cities of the United States," says Rick Watson, a raptor ecologist and director of international programs at the Peregrine Fund in Boise, Idaho.

During the last decade, populations of bengalensis, and the Indian and slender-billed vultures—Gyps indicus and Gyps tenuirostris, respectively—have declined by more than 90 percent in India. Scientists believe that the cause is infectious disease, though no one has identified the pathogen.

Now new research by Peregrine Fund biologists show that at some sites in Pakistan the birds are also disappearing rapidly. "We are losing up to one third of the adult population each year—about three to seven times the normal rate for a raptor population," says Watson. "At this rate bengalensis is well on its way to extinction."

Vultures play an essential ecological role as garbage collectors and recyclers. They rid the environment of carrion, which breed diseases—including anthrax. In Africa, for example, vultures consume more than 70 percent of zebra, wildebeest and other hoofed animal carcasses—not lions or hyenas.

"The Gyps vultures depend exclusively on livestock in India and Pakistan—without them there would be an incredible number of dead animals rotting over the countryside," says Munir Virani, a biologist with the Peregrine Fund's Asian vulture crisis project.

Investigating the Disease

In the Changa Manga forest in Pakistan's Punjab province, researchers say that their vulture study may be over—not because they have solved the mystery of what has decimated the population, but because no more vultures remain.

At Changa Manga the number of active nests has fallen from 198 in 2001 to 49 in 2002 to just six in 2003—a decline of 97 percent, says Virani. Similar declines have been recorded at sites throughout India, Nepal and Pakistan.

About nine species of vultures live in the Indian subcontinent, and each has a specific ecological role. Packs of wild dogs and rats are slowly filling the void left by bengalensis vultures.

In a remote forest region about ten miles from Chandigarh, India, in the foothills of the Himalayas, researchers have just opened a Vulture Care Center. There they will care for sick vultures and try to identify what's killing these species.

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