There is no doubt in my mind that a coyote can and will,if given the oportunity,take down a full grownn deer.I was out doing a job for a local rancher and as I worked my way along the side of a sharp ridge all of a sudden I hear a deer start bleating on the oyher side. I hustle over the ridge and get to where I can see what is going on.Down below me about 50 yards a coyote has a doe by the throat and has her down.I went ahead and shot him off of her and she layed there for a few secounds then got up and kind of half trotted off.She was so exausted that I think that was as fast as she could go.Now our deer here are blacktail and not nearly as large as some whitetail and certinely not as big as a mule deer(an average doe will go about 65-80 pounds)I'am sure had I not interviened that lone coyote would have killed that adult deer.