"Employees of the Union Oil Company of California reported first in 1938 that turkey vultures would gather at the site of any gas leak. After finding that this was caused by traces of ethanethiol in the gas it was decided to boost the amount of ethanethiol in the gas, to make detections of leaks easier"

Aw, I thought that story was going to end with them breeding vast flocks of turkey vultures to patrol the pipes.