In my opinion is you see one coyote then your deer population is affected. One coyote or 4 or 5 it doesn't really matter. I have had a single coyote work up the courage to come into the cattle pasture in broad daylight, trot into the herd and kill a week old calf. I have also witnessed a yote try at a mature calf elk while the mother attempted to fight off the dog. The yote nipped the calf a few times but the cow was able to win the battle. If the dogs want that meal bad enough they will get it. I agree with what was stated earlier that they usually pick on the sick and the lame. Its a natural selection issue which is critical in maintaining a strong healthy population however if the yotes really need dinner they are capable of alot more than we think.