annoying dog

Question
My black lab mix has been sick on and off her whole life recently got lymes disease. she took the meds and seems to be fine except my yellow lab male is obsessed with her hind quarters she is fixed so it is not that. he is not trying to mate it is more like he smells something.  if she lays on the beds of the couch he will lick the area where he hind end was to no end then pee on it. he chases her around the hosueto the point she is freaked out. If she sits he will stop but as soon as she stands he is back at it.  what to do it is getting quite annoying.

Answer
With all her other problems, she could be having anal gland problems.  Have the vet or a groomer empty them.  Neuter the male if not already.  It is no cure all, but helps with many behavior problems and reduces chances of cancer later.  Better leadership might help too.  

The key to most behavior problems is approaching things using the dog's natural instincts.  Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog.  Life is much easier if the 2 legged pack members outrank the 4 legged ones.  You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/  For more on being top dog, see http://www.dogbreedinfo.com./topdogrules.htm