I'll Scratch Your Back, You Scratch Mine?

Horses do this all the time. They "scratch" each other's withers. I came to a screeching halt on my way home because I knew this was going to go somewhere fun. And sure enough, just after I took this photo the horse on the left pulled the horse's tail on the right. Horse people will know that I was entertained for about 5 minuets while these two romped around pretending to be bad. The photo is bad, but the memory is fun.