Donkeys are fantastic watch-animals. Hearing a burro “go off” in the middle of the night - which they do even if a human being they know steps outside to view the night sky - is unforgettable and nobody who wasn’t stone deaf could sleep through it!
Yep, we’ve got a gelded miniature donkey (he’s above breeding size) that is the best watch dog we’ve ever had. We do have two Belgian Malinois, that are great guard dogs, but they keep quiet until you are right on top of them. But the donkey is our early warning system. We even had a small brush fire one night (started by lightning) and he even warned us of that.