Skunks, Racoons, Opossums, Coyotes and the neighbors dogs are all predators who will kill your chickens. In the 8 years we have been raising chickens we have lost chickens to all of these creatures. the worst of the lot have been the neighbors dogs (39 the first time they broke into a run and 51 the second time). We have shot and killed around 30 skunks, 10 racoons, 6 opossums and 4 dogs (the dogs were caught in the chickens run while in the act). My neighbor who is still mad over this whole thing, blames us for having chickens that were in a fenced in yard and another fenced in run where their dogs broke into to get at the chickens...... Of course them not keep their dogs locked up (because you know that's what dogs do) had nothing to do with it. Of course on their property the dog is a pet, on mine it is a predator.
Skunks, Racoons and Opossums will climb a fence with out a problem, they can squeeze through a very small hole. Racoons are very smart and can figure out how to open the door to your coop. On the good side we have not seen or smelt a skunk in the last six months.