In my experience I have found that there is basically 4 types of chicken killers. Type 1 are the chicken eaters. These include foxes, coyotes, bobcats and large raptors. They will hunt birds for their own meal or to feed their young. While some will break into pens and coops, they prefer to stalk and kill birds in the open. Their favorite time to hunt is dusk and dawn but, if the cover is right and during times when they have young, they will hunt during the day. Usually they only take one or two birds unless they happen to get the flock trapped someplace and then a kill frenzy may occur. As a rule they will only kill a couple and if not disturbed eat one right away then carry off the extra. Often too you will only find a few feathers as proof they have attacked. Strong, high fences, preferably electrified, that have buried wire, clearing bush and hiding places and locking birds up a night will deter these killers. Once they have found a food source, however, they will be back until they have cleaned it out or can no longer access it. Type 2 are the chicken pieces and parts eaters. These include raccoons, weasels and mink. They prefer to attack birds that are in a small area where the birds can't escape, generally under cover of darkness when they are roosting. (I have never known of a raccoon attacking a free-ranging. adult bird during the daytime.) They may kill as many as they have time for and eat only part of the body leaving the rest there. Coons, for example, prefer the head and crop while weasels just drink the blood so well that one may not even notice where they slashed the bird's throat. Only by making ones pens tight using hardware cloth and covering any access holes can you protect birds from these predators. Most will take up residence in the area until the chicken population is gone then move on to other kinds of prey. Trapping is a good way to eliminate these animals as well. Type 3 are the opportunist. These are black bears, skunks, possums and snakes. Generally they are in search of something around the chicken coop that is good to eat: chicken food and eggs being the most common. If they happen on birds, especially young ones, and can trap it, they will kill and eat some or all of it. Again, predator-proofing the chicken yard and coop will deter these killers--except that bears will break in. You can trap them but, a good thing is, they don't tend to be persistent but will kill and move on. Type 4 are the kill-for-fun predators. Most are domestic dogs (feral dogs tend to be Type 1) or human--generally teenage boys. They can attack almost any time or place. They will kill anything that they can reach. While they may eat and/or carry some of the bodies away, there is usually a massacre scene of feathers, blood and body parts. While some of the above use of fence and tight coops may work the best bet is to keep your dogs under close supervision and have the number of the local animal control/law enforcement department handy. Perhaps this kind of loss is the hardest to take because there is never rhyme nor reason to it.