Horse makina

You may have seen a horse making a strange expression where it curls its upper lip and bares its teeth into a wide grin. This makes the animal look like it’s laughing. In reality, this is part of a special nose-enhancing technique called a flehmen response.
Horses pull this amusing face in order to direct scents floating in the air toward special olfactory glands that are located at the end of the horse’s nasal passage. The lip-curling and the slight tilting of head help the animal to waft these smells toward these glands. The horse isn’t laughing at you, it’s just trying to determine whether you smell bad.
The “Horse Laugh”
The flehmen response is far more common in male than female horses. Much like giraffes, stallions often sample the urine of mares this way to check if they’re in heat.