I have a few jennys in with my mares, and they are great for keeping ANYTHING out of my pastures. Even the barn cats cant come thru it...without being chased right out! I also have all ranch fencing, so that helps a little with strays too. I really think if you have a coyote, wolf, or a problem along those lines.(going right into the pasture!) ..I dont think the minis would be that halpful, you would probably have to get some standard size donkeys for that. We do have bears, deer, coyotes, etc by us, but I have never seen them in the pasture. I do know with mine, if anything is in there (or something going on that is not normal) mine will bray up a storm, until someone (meaning me or hubby) comes out to check on everything, then they are Ok. I would not be without mine. They have even alerted me,to mini mares foaling, before my equipage system has gone off! Corinne