There is much to guard against when you keep chickens because it seems as if almost every other species would like to eat your chickens. Most of them are four-legged but some of them come in on wings. Therefore, it makes it necessary to build a good strong coop and run. You must be able to close the coop at night to keep out the nocturnal animals. When your chickens are outside the coop in the run they must also be protected because not all the predators are nocturnal.
The first line of defense must be the fence. It needs to be high enough to keep out the high jumpers and it must be buried in a trench to keep out the tunnelers. It is recommended that the trench be at least a foot deep. The fence should be good and sturdy so it cannot be easily knocked down. You also might want to consider laying chicken wire or some kind of netting over the top of your run to protect against Hawks swooping in to the run.
You will find that most of the predators are nocturnal such as foxes, coyotes, raccoons, opossum and skunks just to name a few.
Foxes are especially difficult to guard against because they can jump over an 8 foot fence or they will tunnel underneath the fence. If they are able to enter the coop they will go into a killing frenzy and wipe out the whole flock in one night.
Coyotes resemble a Wolf and will carry a chicken away if they’re able to get into chicken coup.
Raccoons are detrimental to your chickens because they carry diseases. They will also kill them. They normally eat the head and neck of the birds. It is not unusual to find a chicken head some distance away from the coop if a raccoon has been there. Normally they will kill multiple birds when they attack the coop.
The opossums will eat your chickens and their eggs. They will kill and eat near the coop.
The skunks normally go for the chicks and the eggs although they will occasionally kill the chickens.
This should give you some idea of why it is so important to build a good, sturdy coop and a fence around the coop and run. People do allow the chickens to free range around their property and then close them up in the coop at night. If you have a dog and you allow your chickens to free range you will have to keep an eye on the dog and or train it to stay away from the chickens, because dogs are also chicken predators.