Unless you are going to use your pet for breeding, there is no reason not to neuter. There are a host of both health and behavioral benefits to neutering your male pet.
Unneutered male dogs, who reach their senior years, tend to develop prostate problems and often grow tumors on their rectums. Testicular tumors are a common problem in dogs that are not neutered. On rare occasions the unneutered grey-muzzled guys even develop something called a perineal hernia that can turn into a life-threatening emergency.
In addition, for many male dogs that aren’t neutered their avocation seems to be the continuation of the species. The rest is just details. Trouble is he does not have a harem of dogs to rule and dominate. This can build in him a need to be the leader of the pack-even if the pack is your family. Sometimes their frustration is manifested by crankiness, unsocial behavior with other dogs and poor house manners. Often the little guy tries to advertise for the ladies by leaving his scent on the furniture, drapes etc. All that testosterone can actually slow down his ability to focus and learn, too.
Unneutered cats (also called tomcats) are often loving, wonderful, handsome pets. Trouble is they like to advertise for ladies by spraying on vertical surfaces like drapes, couches, etc. Likewise their entire life seems to revolve around eating, sleeping, affection to the family, and “the ladies”. Not to mention, that intact male cat urine is one of the strongest smelling substances on the planet. The odor is potent enough to fill an entire room with the smell, no matter what cat litter you use.Your human friends may stop visiting.
The need to make kittens is very strong in tomcats and they get into ferocious fights with other toms. These fights are over both territory and queens (girl cats). The fights often lead to bite wounds, huge abscesses and other bodily damage. Feline immunodeficiency virus is spread by bite wounds, making tomcats very likely to acquire the disease. FIV is similar to HIV/AIDS in humans, however it is not contagious to humans-just other cats.
Neutering your pet can also help to reduce the overpopulation crisis that is occurring locally and nationwide. Neutering benefits not only your pet, but also your family and the community.