This only pertains to ferrets indirectly as I am replying to the spaying/neutering = longer lives. I think it is an interesting question but it difficult to seperate from the fact that spaying/neutering also implies a more responsible and caring owner. I.e. a person who fixes their kitten/puppy is more likely to ensure other veterinary care, not let the animals out indiscriminately etc. This contributes to longer life than say just letting a Tom cat roam or a female breed indiscriminately which can have negative effects. As to female dogs - it has been proven that spaying before the first heat will drastically reduce the likelyhood of mammary cancer. After each heat the effects of spaying are reduced till at some point (2 years?) spaying will no longer reduce the likelihood. So many ferrets are fixed young (and for good reason) that it would be hard to get a database going on long term effects between non-neutering and neutering. One other thing - people used to neuter dogs and cats around 6 months or later. Only recently have people been doing it significantly earlier. One thing being noticed is that dogs neutered very early (12-16 weeks say) seem to grow taller, leggier. Mary, Booker and the fuzzbutts too [Posted in FML issue 2725]