On Sunday I recognised the signs... Zac became very sniffy and difficult to engage with when we were on our walk, he ignored other dogs even when they were begging him to play. It was fairly obvious someone had been walking a female dog that was in season around our regular walking route. On the way home something more bizarre became apparent, Zac was newly fascinated by bicycles. He ignored a cat to watch a passing bike, he walked backwards down the road rather than lose sight of a bike, then today he was so busy watching a bike he walked into a lamp post. I could think of an explanation but it seemed far fetched. However I got a chance to check it out when I was speaking to a man who lives down the road. I noticed Zac was much more delighted to see him than usual so I asked him whether his dog, Molly (not then present) was in season. She was. Then I asked had he been walking her alongside his bike, sure enough he had. Why Zac has associated the dog and the bike so strongly I am not sure, he has no difficulty being absolutely sure that distant dogs (even ones which bear a resemblance to Molly) are not the one he's interested in but at the moment he has to check out every single bike just in case. I guess he's never learnt to tell bicycles apart before so he has a brand new obsession which I sincerely hope will wear off!