What muscle does a horse use to shake off flies?

Question

What muscle does a horse use to shake off flies?

Answer 1

the same muscles you use when you shiver - small twitchings of your major skeletal muscles, as well as some subcutaneous muscles that are no longer very well developed in humans, like the ones that move your ears and scalp. The small erector muscles that make your hair stand on end and give you goose bumps or goose flesh, are also probably more effective in horses. However I am not a huge expert in equine muscles so there is probably a better answer out there.