Many animal advocacy groups, including the Pixel Fund, heavily promote fixing your pets - and with good reason! Besides being bringing your dog or cat a healthier life, overpopulation is the #1 reason why so many animals are put down every day in crowded shelters.
Health Benefits
Pets that are spayed or neutered prior to six months of age experience more longevity and an overall healthier life than their non-fixed counterparts. Spaying a female dog or cat reduces their risk of uterine infections and breast cancer, which have a mortality rate of about 50% in dogs and 90% in cats (Source: ASPCA). Neutering a male dog or cat dramatically reduces the risk of testicular cancer. Contrary to popular belief, spaying or neutering an animal does not cause weight gain. Your pet will maintain a healthy weight if provided the appropriate amount of food and exercise.
Behavioral & Physical Benefits
Spaying a female dog or cat has both behavioral and physical benefits. Fixing your pet means that they will not go into a heat cycle. A female cat in heat can be difficult to live with. Often she will yowl for a mate, and some may spray urine around the house. A female dog in heat will need panties or diaper to avoid getting bloody discharge on your furniture or carpets. A dam will need to be kept on a leash and supervised when outdoors, as intact male dogs will do just about anything to reach a female dog in heat. Neutered males dogs and cats are much better behaved than a their un-neutered counterparts. Aside from avoiding embarrassing leg humping, neutered male dogs are less likely to run away from home as they are not in constant search for a mate - this includes not yanking your arm off when you are walking your dog past a potential lady friend and not digging an escape route under your fence like your backyard is Alcatraz. Neutered dogs are completely devoted to their humans, whereas un-neutered males can show tendencies of aggression and can be territorial. They may spray in your house and fight with other male dogs or even people. If a male dog is fixed after this behavior starts, sometimes it can be too late. Un-neutered male cats may be the worst from a behavior standpoint. They wale and cry to be let outside, they spray urine all over your house. The stench of feline urine alone is often enough to persuade someone to fix their cat. Additionally, tom cats will fight over females, they will fight over their territory, they will fight to let off steam. This puts your cat at risk for serious injury.
Overpopulation
The American Humane Society estimates approximately 3.7 million animals are euthanized every year. Many others suffer on the streets as strays - often emaciated without shelter or adequate nutrition. These extraordinary numbers are due largely in part to the frequency of unwanted or unplanned litters.
Money
From a financial standpoint, paying to have your dog or cat fixed is much more cost-effective than the potential financial repercussions of leaving him or her in tact. Caring for an unexpected litter or kittens or puppies is very expensive. You also avoid the expense of caring for injuries incurred by your male dog or cat from the fighting with other animals.
Reducing the Number of Strays
The life of a stray cat or dog is heartbreaking. These domesticated animals are unable to care for themselves and often die from starvation, exposure, or fall prey to wildlife. Only 10% of strays brought in off the streets are fixed. In addition, stray animals can be damaging to the community. The ASPCA notes that stray animals can "prey on wildlife, cause car accidents, damage the local fauna and frighten children." The #1 way to keep animals off the streets is to reduce the amount of unwanted litters.