I have a problem with Kilo trying to hump labradors. Not just any labradors, but specifically black or chocolate ones. Other breeds of dog and fox red and yellow labs are safe from his attentions. This evening Kilo was playing on the field with his vizsla friend when a black lab came tearing over and Kilo immediately tried to hump him. This has also happened a few times within the last fortnight - the labs have always come tearing over and he has always immediately tried to hump. It does not make any difference whether they are dogs or bitches. When he was younger he would sometimes try to hump dogs out of pure over excitement when play got a little too exuberant, which stopped quite a few months ago (probably about 6). It sounds a little odd, but the only 'lab related' incidents that I can recall was the black lab that came tearing over and knocked him down around 3 weeks ago (I think) or (more likely maybe) the two chocolate labs that tear over on a regular basis, one of which who was in season a fortnight or so ago and gave us problems. When he shows any signs of wanting to hump he will 'leave it' if asked but just tries again and again if left offlead. At present I put his lead on and remove him from the dog. If the owner is willing and he is let off again, he tries again straight away. He gives up immediately if one of his victims growls or gives an air snap and doesn't attempt anything again. At present we don't meet labs whose owners ask if they can play; they all come running over - if the owners asked me I would probably ask that they don't play or are introduced calmly (and explain why) until I can get to grips with this behaviour so Kilo doesn't get the chance to rehearse it. Any advice?