We had ours fixed at about 7 months.. Male, now 11 months old. 2 days ago he stole a duster and was humping it. How that is possible I don't know. I took video to show the vet. ( It was after he was done twirking ). I don't know I should laugh or cry. He stayed just as aggressive neusence that he was before being fixed. My son thinks the vet missed something