To stop predators, I once saw on tv or read some where that taste is the greatest method. Smell and taste trigger memories the best. Based on this concept farmers/ranchers would sacrifice a lamb or calf and then poison the carcas. The wolves or coyotes would get deathly ill, but not die. And since taste and smell are the greatest triggers to memory, they wont even think about attacking the same animal because or the horrible poisoning experience.
It works on us as well. If we have a stomach bug that we dont know about then go to eat. Later we get sick then we blame it on the food. Based on that smell/taste trigger if someone suggests going out to eat at the same place or eating the same food in the future your responce is usually "Their food makes me sick." Even though their food probably didnt do it, but that trigger is hard to break.
"The Marines I have seen around the world have, the cleanest bodies, the filthiest minds, the highest morale, and the lowest morals of any group of animals I have ever seen. Thank God for the United States Marine Corps." Eleanor Roosevelt, 1945