Luckily we don't have fox problems. . . Or foxes for that matter, I believe. I mean I think we do, just not in our vicinity. Coyotes - Yeah. Hear 'em howl and whine all the time, but have never seen any or had any troubles yet.
I think the chair killed the fox. I killed a gray fox by hitting it in the back of the head with a small rock. Their skulls are pretty fragile. Then the chickens did what comes naturally, They beat up the limp invader.
My pullets would run from my cats when the pullets were younger, but now they are big and not afraid. Not too long ago, I got two 17 week old Red Sex Linked pullets and from day one they were aggressive, even chasing and trying to attack the cats - a queen around 6 pounds and a tom around 11 pounds. One tagged my queen as she ran by, so now the cats are afraid, but I am also there watching and telling the cats not to hurt the chickens. I even have video of the cats and chickens hanging around together.