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Tuesday, September 6, 2016

A Vanishment of Vultures

There was really no way of telling what the wildebeest had died of, or how long it had been dead.  To tell you the truth, we could barely tell that it had once been a wildebeest at all.  The entire surface of the carcass seemed to be swarming beneath a carpet of black or brown wings, with naked heads occasionally popping up like periscopes.  Even as our guide edged us off the dirt road for a closer look, more and more vultures descended upon the quickly disappearing bovid.  With what I could swear was a slight smirk, one hopped onto the long nose of the wildebeest and, with a deft flick of its beak, extracted an eyeball, which it tossed back with every sign of relish.

We'd seen a lot of exciting wildlife on that safari to Tanzania.  Much of it was endangered - cheetahs on the Serengeti, elephants in Tarangire, black rhino in Ngorongoro.  Sometimes we'd get sentimental as we sat around the campfire, wondering how much longer some of these animals would remain wild in Africa.  One group of animals that it never occurred to me that we might have to worry about losing were the vultures. 

That was my mistake.

The vultures of Africa and South Asia play an undisputedly important role in their ecosystems.  To them falls the task of clearing up the carcasses of other animals, especially large mammals.  Without them, environmental contamination, maybe disease, could decimate other species.  As important as they are, however, they remain little studied compared to the more glamorous large mammals upon which they feed.  No one was paying too much attention to them... until they started to vanish.

It started in India, home to nine vulture species.  One of them, the Oriental white-back, was the most common raptorial bird in the world, emphasis on the "was."  Suddenly, the carrion-eating birds began to vanish at a rate believed to be the quickest avian decline ever recorded.  For the longest time, no one could figure out why.  No one was hunting them.  There was no evidence of infectious disease.  There was plenty of food to eat.  What could the problem be?

It turned out to be the food, a problem that was solved only when the vultures of South Asia were already almost wiped out entirely.  Diclofenac, an anti-inflammatory drug, had been introduced for use to India's enormous cow population.  It turns out that Diclofenac is good for cows, but not so good for vultures - lethally toxic, as a matter of fact.  Vultures who dined of deceased cows that had Diclofenac in their systems died in droves.  Since many dozens of vultures would congregate at a single cow, even a relatively small number of cows with the drug in their systems had the potential to contaminate enormous numbers of birds.  Three species of vulture, including the formerly omnipresent white-rump, saw their populations drop by over 95% in just a few years.

The loss of the vultures impacted India in other ways.  Nature abhors a vacuum, it has been said, and the disappearance of the vultures led to an explosion in the number of feral dogs and rats who took on the scavenger niche.  The difference between dogs and rats and vultures, of course, is that the later doesn't also carry rabies.  Even the mammalian scavengers couldn't keep up with the backlog of carrion, and anthrax and other diseases soon spread, requiring vast expenditures of money to combat.

One of the most striking side effects of the vulture decline has been on the Parsis, a Zorastrian community.  Parsis traditionally disposed of their dead by leaving them on special elevated platforms called "Towers of Silence", where vultures would consume the dead and return their bodies to the earth.  A lack of vultures caused the practice to fade away.

Fortunately, India - along with neighbors Nepal and Pakistan - rallied to action.  New drugs were developed and, following tests on captive vultures, deemed safe.  It is hoped that the Asian vulture crisis will slowly right itself out... but it will take some time.  Vultures breed slowly, and they lost a lot of ground.

The situation in Africa has a similar key point - vultures dying from eating contaminated carcasses - but the stories diverge there wildly.  The key difference is that in Africa, the poisoning is deliberate.  For millions of years, lions, hyenas, and other mammalian predators have used the sight of circling vultures to help them identify distant sources of carrion, which they could then run up and appropriate.  In East and South Africa, game wardens and park rangers use the same trick to catch poachers - look for the vultures that are circling over a recently killed rhino or elephant.  In order to remove such telling signs of their crimes, some poachers have begun pouring poison over the animals they kill.  Leave no witnesses, one might say.  Four African vulture species are now listed as Critically Endangered by the IUCN, with others listed at other levels of endangerment. 

Zoos have been involved with both vulture crises from the beginning.  It was a biologist from the London Zoo that first studied the causes of vulture decline in India.  The new, safe Diclofenac substitute was tested on captive vultures.  Zoos maintain captive insurance colonies for several species of Old World vulture, which may be possible reservoirs of candidates for future reintroduction programs, similar to that which saved the California condor.  And zoos have been a leading voice in educating the public about this disaster and raising support (and funds) to solve the problem.

Vultures won't win too many popularity contests, for reasons that I can never understand - they are truly extraordinary birds.  Whether or not one finds them beautiful, however - and there is no accounting for taste - their impact on the ecosystems that they call home is undeniable.  To risk losing vultures wouldn't just rob the Asian and African skies of some of their most majestic inhabitants.  As we saw in India, it could trigger environmental, social, health, and financial consequences that affect all species - our own not least of all.

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