turkey vultures have knowing noses, and used the birds to locate leaks in natural gas lines. The engineers had figured out that if they introduced ethyl mercaptan into the line, they could locate leaks by the concentrations of turkey vultures circling above the line or sitting on the ground next to it. The same sulfurous chemical added to natural gas so the human nose can detect a leak, it turns out, is also released by an animal shortly after it dies.
