There are many benefits to spaying (females) and neutering (males) your pets. Spayed females will no longer have heat cycles, which will reduce their desire to roam because there is no need for them to find a mate and males will not be attracted to the area when looking for a female in heat. Health benefits of spaying include a reduction of mammary gland tumors, ovarian cancer, and uterine cancer or infection. If spayed before their first heat cycle, the risk of ovarian and uterine cancer, as well as uterine infections can usually be eliminated completely.
Neutered males have less desire to roam and find a mate, and thus are less likely to be injured in fights or hit by a car. The risk of testicular cancer is eliminated once a pet is neutered, and the risk of prostate disease is reduced. Neutering your pet can also help decrease aggressive behavior, especially when around other unaltered pets.
Dogs and cats that have been altered can also live longer lives. Altered dogs live an average of 1-3 years longer, and cats live an average of 3-5 years longer.