How does neutering affect a dog's behaviour?

Neutered individuals are less likely to stray off, simply because they do not have the same hormonal urge to mate. They also tend to be less aggressive with other dogs, although this is not necessarily true in all cases.

Breeds that were originally bred for fighting purposes, such as the bull terriers, may continue to scrap with other dogs if the opportunity presents itself. It will take perhaps six weeks or so for such changes in behaviour to become clearly apparent.