I think I've only seen 1 Mustang so far. Really? We have 2, and I know several other people who have rescued Mustangs. They're so very hardy, smart (and talk about "trail-wise"!), sure-footed, and on and on...
Oh yea, they can be a bit "bull-headed", but I think that's because of their survival instinct. You really have to convince them that you are trustworthy of their efforts. Trust is everything!