Removing the male’s testicles not only prevents unwanted litters, but it also has health benefits like eliminating the risk of testicular cancer and reducing the risk of prostate problems. Neutering male dogs and cats reduces roaming, marking, and aggressive behavior. What it does NOT do is change your pet’s basic personality. Aside from these positive changes, your dog will be no less like himself than a male human is after undergoing vasectomy. For an animal, sex is nothing but a powerful instinctive urge to reproduce. Dogs and cats are much healthier and happier when neutered, and don’t suffer any kind of identity crisis or emotional reaction like a human would. It is a dog’s natural instinct to protect his home and family, and this will not change after neutering. Genetics and environment are much more influential in forming his personality than sex hormones.