Circling the Drain

India's once-ubiquitous vultures have nearly vanished. A dozen years ago, the scavengers numbered in the tens of millions and darkened the skies over Delhi as they wheeled above the city in soaring columns. But a pain killer widely used in cattle has led to an unprecedented decline. Today, the vulture population is estimated to be in the low thousands and hovering perilously close to extinction. Their disappearance has led to a rise in feral dogs and rats, which are now the dominant scavengers, and rabies is a major concern. A substitute cattle drug, non-lethal to vultures, has been developed, but it is more expensive than the deadly drug and not yet widely manufactured. Conservation biologists fear it may already be too late.