Vulture World- From a continuing series on revolting creatures. By Constance Casey

More revolting creatures: the tick and the jellyfish.

A vultureA few weeks ago, I spent a surprisingly pleasant morning watching vultures in the "Birds of Prey" section of the Bronx Zoo in New York City. The birds, juvenile females named Patsy and Dolly, were calm and curious, dropping down to the front of the cage every time someone stopped. When lunch came, they used their big, flat feet to steady packages of recently thawed rat carcasses as they undid them with their hooked bills. (Zookeepers wrap the dead rats in paper, tightly tied with string, to make the dining process more interesting.) A point of contention with the zoo categorization of Patsy and Dolly: They aren't really birds of prey—they're birds of clean-up.

What would happen without them? The major vulture news of the last decade gives a clue. A mysterious die-off of Asian white-backed vultures has led to a pileup of domestic animal carcasses and an increase in the population of rodents and feral dogs. It turned out that an anti-inflammatory drug—diclofenac—used on sick livestock kills vultures even in low doses. Though the Indian government is phasing out the veterinary use of the drug, the vulture population hasn't rebounded. One social consequence has been that members of the Zoroastrian Parsi community, who have used vultures to dispose of human corpses, now have to cremate their dead. But that doesn't solve the problem of animal carcasses in a vulture-free world. Let's be grateful the turkey vultures are keeping us from being awash in dead raccoons.