He pointed out that the caption from yesterday's photo might not make sense without some explanation.
Horses have fairly small, pricked ears. Donkeys and mules have rather longer ears. A horse's ears aren't just for hearing the carrot bag rustle - they're an important part of how equines communicate.
First of all, the direction a horse's ears point in indicates their primary attention.
Both of this horse's ears are pointed right at the camera. His head is also turned that way, meaning his attention is entirely on the camera and the person holding it. Pricked ears show alertness and usually happiness - a horse with both ears pricked is "smiling."
This pinto, on the other hand, is more interested in the hay he's eating. He has not turned his head, but has the ear on that side cocked towards the cameraperson. His attention is split between them and his lunch.
This picture shows divided attention even more clearly. One of the mare's ears is pointed at the camera. The other is pointed at her rider - listening for the next cue.
What you'll often hear is that ears back means a horse is unhappy - in this case, the back-turned ear is still "pricked" or "upright" and shows that she's paying attention to the person on her back.
This horse is slightly annoyed - instead of being pricked but turned back, her ears are slightly flattened and the rest of her expression is grumpy. She's been tied up longer than she likes and isn't entirely happy about it.
Be careful about approaching a horse that looks like this. They may decide to make you a target of their irritation. These Przevalski's horses are having a hierarchy dispute. Note the completely flat ears on the middle horse. We call this "pinned" ears.
If a horse puts its ears flat back like that - back off! That's a horse that is either scared or aggressive - and in either case quite likely to bite you. An expert who knows how to handle a horse in a bad mood can do it. A novice should not. As a note, a horse pins its ears to protect them from damage in a fight - so war horses in battle will also pin their ears. Don't pet a horse that has its ears pinned. It's probably trying to say "Don't pet me."
Mules and donkeys use the same "ear-lage" to communicate, with one slight exception.
If my horse had its ears flat out to the side like that - then I would be worried. Horses only flatten their ears sideways if sick, exhausted, or depressed (Yes, horses can get depressed. I've seen it). Mules, however, tend to just let their much larger ears flop casually - it just means relaxation. In this case, this mule was just too lazy to be bothered to prick them.
(All pictures taken by me unless specified otherwise).