Mulder's the only male we ever had and we never did neuter him. He was very well behaved, never marked in the house (which is more a training issue than anything else) and while he was an inveterate humper I don't think that was sexually triggered. He even lived with intact bitches with no problems and no bad behavior although I of course had to separate them when they came into heat. In terms of negative attention from other dogs, I found it to be the worst around his adolescence (10-18 months or so). Once he was an adult and over the teenage hormones that seemed to settle as well.