Millions of dogs and cats are killed every year due to pet overpopulation. Many of the unwanted animals are the direct result of unplanned, unwanted breeding. Altered animals live longer, healthier lives. These surgeries prevent certain cancers, infections, and other illnesses. Altering often leads to positive changes in pets. Neutered male cats and dogs are less likely to mark their territory by spraying or urinating. Spayed female cats do not yowl to attract mates. Sterilized cats and dogs are also less likely to roam and get hit by cars, eaten by coyotes, hurt from fights, etc. If you have a female cat or dog, it has been identified as being spayed by using a drop of tattoo ink at the incision site. This helps veterinarians to know that your pet has been spayed.