Horses have great hearing. In fact, hearing and flight are the two main components of the equine survival system. If a horse hears a sound that’s even remotely unusual they’re wired to react, sometimes instantly. Their natural response is to run away first, ask questions later. That’s how they’ve managed to survive through the ages. Some horse breeds are slightly less reactive to sounds while others have evolved with the quick responses of their ancestors still 100% intact. That’s neither good nor bad, it’s just important to consider when choosing a mount.
Dharla is highly reactive to sound while Bullet is somewhat less so. If Bullet seems concerned about a sound he’s more inclined to want to investigate the source than flee from it. Usually, but not always. Dharla’s not a total chicken, but she’s going to put a safe distance between herself and the sound before she gives it the benefit of the doubt. Horse are usually somewhat braver in a herd situation. It’s a safety in numbers kind of thing I guess. Then again, I’ve seen horses feed off each others fear, so you never know for sure how a group will react.
Above, I caught both horses listening intently to something just out of their sight, behind the arborvitae. It could have been a bird or a chipmunk, but as far as they were concerned it might have been a rhinoceros, too!