In a parallel effort, other USDA scientists are working to develop scent attractants to ensure targeted delivery of whatever prophylactic their colleagues come up with. It's not as easy as you'd think. "Coyote management requires specialized attractants to target the delivery of drugs and vaccines, and for the effective operation of traps," says Bruce A. Kimball, PhD., principal investigator of the study and a chemist with the USDA's National Wildlife Research Center in Fort Collins, Colo. "Attractants must provoke behavior that will make coyotes respond appropriately." In other words, attractants have to bring coyotes to the birth-control dispenser and then make them roll and scratch in the substance, creating a delivery method for the drugs. Researchers have noted that different scents or combinations elicit different behaviors in coyotes. Some scents produce rolling, others rubbing or scratching, and so on.