Vultures. Cartoon characters in parched deserts often wish them to disappear, since circling vultures are a stereotypical harbinger of death. But, joking aside, vultures in some parts of the world are in danger of disappearing. And according to a new report from University of Utah biologists, such a loss would have serious consequences for ecosystems and human populations alike. The primary threat to vultures, according to the report published today in Biological Conservation, is the presence of toxins in the carrion they consume. On many continents, vultures are the unfortunate victims of poisoned carcasses -- especially impactful because dozens -- or even hundreds -- of vultures can feast on a single carcass. Populations of most vulture species around the world are now either declining or on the brink of extinction.

Losses of vultures can allow other scavengers to flourish, according to biologists Evan Buechley and Ça?an ?ekercio?lu. Proliferation of such scavengers could bring bacteria and viruses from carcasses into human cities.

Risk factors for decline

In 2004, ?ekercio?lu published a study examining the respective extinction risks of all bird species throughout the world. He noted then that vultures represented the single most threatened group of birds. Now, more than a decade later, Buechley and ?ekercio?lu have examined factors affecting the extinction risk of more than 100 bird species, including 22 species of vultures, which eat carrion exclusively, and other scavenging birds that have broader diets.

Their results suggest several inherent ecological traits that likely contribute to vultures' extinction risk, including their large body masses, slow reproductive rates and highly specialized diets. The greatest external threat to vultures, however, is poisoning.