Weird question?

Question
Hi Shannon,
         Well, this is not a necessary question but I was just wondering; Why do dogs chase there tail?  

Answer
Hello Jesse,
          Well after you've been saying I went on wondering and heres what I came up with;
Because they're there, of course. Watch a dog as it chases its tail, and you can almost hear it thinking, "What is this thing that keeps following me around, and why can't I catch it?"
Quantifying canine intelligence is a very tricky business; there are dogs that display great
aptitude for obedience work yet don't have the sense to come in out of the rain, and dogs that are seemingly untrainable yet exhibit astonishing reasoning and decision-making powers.If you have any more questions like this you can go ahead and ask!
                                  -Shannon