I've always heard it's because they've found something that's smelly and dead. One day in the park, a bunch of humans were standing around looking at what seemed to be a perfectly innocent patch of grass... but almost every single dog went over and rolled in it at some point. Whatever it was sure must have been gross!
I think this is different from when they rub their heads on the floor. That, I think, is to dry their faces off.
__________________ If you love something, set it free. Unless it's an angry tiger. |