Running in Circles

Why is it that when I take Rockie out to go poop he must run around the yard in circles? Then he spins in a circle settles down into the squat position and goes. I just don't understand. I have never had to run in a circle before I go, I have however had to run and have had the runs but never had to run in a circle. Just one of those things that makes ya go hmmmmmmmmmmmmm