I have been finding dog turds distributed randomly around the general office. The culprit is a charming terrier who frisks around the place during the day. No one wishes to see the dog expelled, particularly because it belongs to an important and delightful member of the staff. Nor do we wish to inform the Health and Safety officer or any of upper management. None of us has had the courage to mention the terriers deposits to his mistress, for fear of seeming rude.
Violence can go a very long way both in the short run and in the long run.
Still, if you must keep it non-violent, here is what I'd advise. The next time you come across the dog's, er, unwanted belongings I would secretly and carefully transfer it to the area near or underneath the owner's desk. Try not to muck it up, you want it to look as natural as possible. Carry on with the practice until you see results. Under the circumstances, I don't think this last resort is all that rude or uncalled for.