It is called 'conditioned taste aversion' (CTA). A chunk of mutton is laced with 'a very specific dose of an undetectable nausea-causing substance', then wrapped in wool and left out for the predator to find. After the severe nausea passes, there is a permanent memory of the result of eating that kind of prey, and they make a point of avoiding that prey regardless of other circumstances.
For more info on Jonathan G. Way's coyote research, to to http://www.easterncoyotereserach.com
I just ran across this website http://www.llamas.co.nz/guard.htm, and there seems to be a lot of conflicting opinions. I heartily disagree with the person who says that coyotes don't hunt in packs!
Susan Monroe wrote:
of salty-tasting Lithium Chloride
"Predictably, predators that consumed salty-tasting meat baits, refused to eat salty meat baits again after recovering from illness (showing that CTA had indeed been produced), but continued to attack and consume non-salty baits or live prey."