I needed about 200 feet of 48" 1/2 in hardware cloth for my rat-proof chicken world (which is roughly half-done at this point...).
I used TWP inc, which is actually a wholesaler (great deals for multiple rolls) but they will sell 1-2 rolls as well.
Here is the section in hardware cloth...
The 4 square feet per chicken is taking a near-industrial ag approach ( "modern" industrial farms are even denser than that!). I would agree with the 10-20 square feet per bird. I have 7 in about 350 square feet, and they have almost too much room! They all hang out right next to each other...
The rats are not just attracted to the feed (though they can definitely get to that). Chicken poo is also plenty delicious to a rat. You should see how my dogs happily chow down on chicken poo.
Rat poison works by disrupting blood clotting mechanisms that are unique to mammals, so it is...