Once, at a dog park, I witnessed a chihuahua-sized dog do a handstand in order to pee higher on a tree.

My Australian Cattle Dog is a total hoss, very confident and often scares other dogs just by casting a serious look in their direction. Even though he's a medium sized dog at best, he never cocks his leg when he pees. Given his confidence maybe he just doesn't see the need to lie.

Is this caused by natural selection, or are they smart enough to do this intentionally?