Bunnylady
Herd Master
If the fox is getting to the chickens, your fences are definitely part of the problem.
My mini mule has tried to attack chickens (fortunately for them, they are quicker than she is), and has probably managed to connect with a couple of ducks. Mules and donkeys protect their territory, not so much the animals inside them, and are known to get nasty with anything they think doesn't belong (sometimes including new members of species they are already familiar with). Also, they don't "patrol," and if the fox comes while they are sleeping, it can literally get away with murder.
The only animal that will reliably protect chickens is you (I think greybeard's list are names of guns named after animals)
My mini mule has tried to attack chickens (fortunately for them, they are quicker than she is), and has probably managed to connect with a couple of ducks. Mules and donkeys protect their territory, not so much the animals inside them, and are known to get nasty with anything they think doesn't belong (sometimes including new members of species they are already familiar with). Also, they don't "patrol," and if the fox comes while they are sleeping, it can literally get away with murder.
The only animal that will reliably protect chickens is you (I think greybeard's list are names of guns named after animals)