Not a prairie dog hole, but in my youth Dad lost a cow that stepped on a piece of earth that had been undercut by running water while walking down a gully. The cow’s front leg went through and she crashed her chest against a sapling tree. Don’t know if the fall killed her (probably not) but she died in that position. We found her as a cowhide bag of bones. The “step” from where she lay to the next level of ground was only two feet or so.
So hazardous ground can claim livestock.
First, zombie.
Second, horses can be some kind of stupid. I have personally witnessed a horse rear up on passing through a gate he had passed likely hundreds of times, over balance, hit his head, and die. Why, no idea.
I am unconvinced that the fact that no one tracks how many horses step into holes means that horses don’t step into holes. They’re big and remarkably fragile at the same time. Not sure that the fact a horse got injured regularly makes the news. Unless it’s fallen into a well. And that seems to happen with odd frequency come to think of it. Which may mean something in this context.