Ass to mouth

(Disclaimer: This is not my dog.  My dog is actually gorgeous)

My dog Dolly is a little over 13 years old.  I've had her since she was 1 year.  She has never been forced to skip a meal and by all accounts would be considered "over-fed".  So, how is it that I will still see her in the garden rooting around for remnants of her own feces?  I can occasionally forgive her eating cat shit, but her very own poo?  Seriously? 

Don't kiss me with that mouth.

Love,
Katie