Foxes and chickens just don't mix. If you're one of those unfortunate owners of backyard chickens who have seen first hand what a fox can do, be sure to fox proof your current chicken coop. It is horrible to see what a fox can do in just a short period of time inside your coop. You'd be surprised how many city people don't even consider foxes when setting up their chicken coop. There are many reports of foxes in urban areas, so don't assume that foxes are only for rural areas.
As manufacturers of mobile chicken coops, we've had many customers tell us about the brazen foxes in their area. Some come as close as their back porch in the early morning, and that's in a metropolitan area! Don't wait until you see a fox in your area, or hear of a fox attack before you safeguard your chickens.
The best way to keep foxes out of your chicken coop depends largely on the style of coop and run that you have. Foxes mainly gain access to mobile chicken coops by digging under the edge of the coop and tunneling under to reach your chickens. Even if you're on reasonably hard soil, foxes can be quite determined to access your coop.
One of the best things to do in this case is to wire a large mesh floor to the base of your coop. If it's attached to the base itself, it will be able to be moved along with your coop when you move your chickens to a fresh area of your backyard. It's important to make sure the mesh you use is still large enough that your chickens have room to scratch, but small enough to keep foxes out. In our experience, mesh that is 10cm x 15cm works really well. Installed correctly, we've not had any reports of foxing entering a coop with mesh of this size fixed to the base of the coop.
Another option is to fix a mesh 'skirt' around the outside of your coop. This gives your chickens more freedom to scratch, but makes moving your coop a bit more difficult We've tried both methods and the skirt is very cumbersome, but may be the preferred option by some.
It's also important to make sure that your mobile chicken coop is made from strong enough mesh. Unfortunately, some of the imported coops that I've seen on the market are made using very light 'aviary' style mesh. We've been told of foxes that have chewed through this thin mesh to gain access to the chicken coop. So just make sure that the coop you purchase, or make, has strong enough mesh. I would suggest mesh that is 2.5mm thick. We've found that this cannot be damaged by foxes trying to chew through, or children who love chickens and clamber all over the chicken coop!
If you haven't got a mobile coop, but a more traditional style coop that stays in a fixed position, you want to be sure that the run that is attached to your coop is fox proof. Most people with a traditional chicken shed and run erect a permitter of high chicken wire to form the run. This wire should have holes no larger than 80mm in diameter. As this style of run generally has no 'roof', it's important that the walls are high enough to prevent a chicken from flying over as well as to prevent a fox from entering (around 1.8m high is generally adequate).
When your run fence is erected, you also need to make sure that the wire at the bottom of the fence is dug into the ground, not too far below the surface, to a distance of about 50cm. As mentioned, foxes will dig to gain access to your chicken coop. When the foxes come across this wire time and time again, they'll eventually give up trying to access your chicken coop. Another way of achieving this barrier is to but something heavy like wooden or concrete sleeps on top of the mesh at the bottom of your fence.
If you're after a mobile chicken coop that keeps your chickens safe and protected from foxes, be sure to have a look at the range Royal Rooster. These are made from aluminium, are durable and look great!
I've been looking into this myself, there are a few good pages with more info for anyone that's interested...