A white-backed vulture sits in front of a hooded vulture atop a dead tree snag perch at sunrise at Thornybush Game Reserve in September 2016.

One of our September early morning wildlife drives at Thornybush Game Reserve near South Africa’s Kruger National Park yielded some good scenes of white-backed vultures (Gryps africanus) and hooded vultures (Necrosyrtes monachus) feeding at a dead blue wildebeest (Connochaetes taurinus). Vultures are viewed with suspicion and disgust in the western world, which is undeserved since they are extremely important to the proper functioning of ecosystems worldwide. By removing putrid animal carcasses, various vulture species greatly reduce transmission of diseases such as rabies and anthrax, control populations of such pests as swarming flies, and generally improve sanitation and nutrient cycling in the ecosystem.

White-backed vultures are large, weighing 9 to 16 lbs (4 to 7 kg). This one is feeding upon a dead wildebeest, probably not killed by lions and instead having died of hunger thanks to the ongoing 2016 Southern African drought.

Many Asian and African societies hold vultures in high regard, unlike Western ones. Unfortunately, both white-backed and hooded vultures and most other species worldwide are endangered, many critically. Extinction is a real possibility for about half of the world’s 23 species. Threats include loss of habitat, hunting, and poisoning.

Hooded vultures are smaller than white-backed vultures, weighing 3.3 to 5.7 lbs (1.5 to 2.6 kg).

The last threat is extremely insidious since vultures have to feed upon dead animals by their very nature, and when people add toxic chemicals to a carcass a single poisoning incident can result in the death of dozens or even hundreds of birds. Why does this happen? For example, sometimes people in Africa poison a cow carcass with inexpensive and readily available carbofuran pesticides as retaliation for the cow’s death caused by lions, hyenas, or other predators. So while the vultures are not the intended target, they are nonetheless the victims. Other times elephant and rhino carcasses are purposely poisoned by illegal ivory and rhinoceros horn poachers, in an effort to kill the vultures specifically. The reason for this is that oftentimes park rangers and wildlife conservationists use flocks of gathered vultures at a dead elephant or rhino to locate and track the activities of the poachers, so the poachers kill the birds to avoid detection.

Many birds have a third eyelid called a nictitating membrane, which closes over the eye sideways. It is a translucent or transparent membrane that functions much like normal eyelids do, but helps maintain visual awareness at all time. This vulture was caught in mid-blink and is not blind.

And finally, an antibiotic drug known as Diclofenac which is used to prevent diseases in domestic cattle in India has proven to be extremely toxic to various South Asian vultures. When the cattle die, in many places only vultures and feral dogs are available to dispose of the corpses since most Indians don’t eat beef and the widespread poverty of the country precludes a civic solution to the problem such as burial or rendering. There used to be millions of vultures in India, and the birds were recognized as important to maintaining public health. But because Diclofenac poisoning has killed 90% of vultures there since the 1990s, cattle carcasses now linger for weeks longer than they used to. This has led to explosive increases in both fly populations and in feral dogs. Rabies is rampant amongst Indian feral dogs, and in 2015 there were about 59,000 human deaths caused directly by rabid dogs biting people, a rate far higher than anywhere else on earth.

The skull of a wildebeest lies in the bush, weathering to white with time.

The link between vulture declines and Indian rabies cases should help prove the value of these birds to a healthy ecosystem and social structure. We must take measures to ensure that vulture populations are maintained and return to more normal historic levels. Their importance is underappreciated!

There were about a dozen vultures of two species at this particular wildebeest carcass, feeding just as the sun rose on a chilly early spring morning.

The same poisoning issue can occur with other large vultures elsewhere, including here in the United States. Critically endangered California condors (Gymnogyps californianus) have also been suffering from toxic diets for decades, and in fact poisoning contributed heavily to the species’ near-extinction in the 1960s, 70s, and 80s. Although in US cases it is lead buckshot and bullets used in hunting that is the problem, not Diclofenac or other pesticides. Hunters using lead ammunition to kill all sorts of animals left bullets and shot fragments in the entrails of big game they field dressed and cleaned. The condors feeding upon these gut piles ingested the lead and over time the toxicity built up to devastating levels, crippling and killing numerous birds. Again, this was not intentional, but there you have it anyway.

A visual comparison between the white-backed vulture on the left and the hooded vulture on the right.

California condors went extinct in the wild in 1987, and for some time only remained in captive breeding programs. They have since been reintroduced to parts of central California, southern Utah, northern Arizona, and northern Baja California, Mexico. Populations are still critically low but are gradually increasing. Meanwhile carcass lead poisoning is still hampering recovery efforts, although progress is slowly being made as lead ammunition is declining over time in favor of nontoxic steel ammunition.

 

A desiccated Cape buffalo carcass (Syncerus caffer) dries in the African sun. Once the rains return later in summer, the skin will soften and probably be consumed by scavengers. For now the leathery hide is left intact since it is too hard and tough to deal with.

Meanwhile Andean condors (Vultur gryphus) aren’t quite as rare in South America as California condors are here, but they too are having trouble surviving the modern era. For birds that thrive on dead animals and carcasses filled with bacterial waste and putrefaction, they sure are vulnerable to poisoning from other substances! We need to factor this vulnerability into conservation plans for these important birds, and we need to better understand their valuable role in the natural cycles that keep the ecosystem healthy, as well as human societies. We lose vultures at our own peril. Most ironically, their deaths might well presage our own!