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Effects of Neutering on Behavior
Neutering is the surgical procedure that renders a male or female cat or dog unable to reproduce. In males, the surgery (called castration) entails removal of the testicles, leaving an empty scrotal sac that soon shrinks. The testicles produce sperm and are the primary production site of the hormone, testosterone. The penis is not removed because it functions additionally for voiding urine. In females, surgical sterilization (commonly called spaying) involves removal of both ovaries and the uterus by incision into the abdominal cavity. The ovaries produce eggs at each "heat" cycle and also produce the hormones, estrogen and progesterone. The uterus is also removed because it may later become infected if it is not removed. These surgeries are done under general anesthesia. Pets are neutered so as to prevent undesired births and a variety of medical disorders in both males and females. Ideally, females should be neutered before their first estrus. More pets are being neutered at younger ages so they do not contribute to overpopulation. Speak with your veterinarian for recommendations regarding your pet.
Effect on Sexual Behavior
Sexual behavior usually disappears after neutering. In animals that have experienced sexual activity before neutering, however, some sexual behavior may persist. This is not necessarily an indication of incomplete surgical removal of the sexual organs. Behavior that appears to be sexually motivated may be linked to other causes. Mounting by castrated dogs, for example, is usually a sign of dominance behavior. Masturbation, particularly in male cats and dogs, may occur following castration. This is most common in males that have experienced sexual arousal before castration. For most pets, however, neutering effectively eliminates development and progression of objectionable sexual behavior.
Effect on Aggression
Intact (unneutered) males and females are more likely to display aggression related to sexual behavior than are neutered animals. Fighting, particularly in males and directed at other males, is less common after neutering. The intensity of other types of aggression, such as dominance aggression, is also likely to be reduced. When related to the hormonal imbalance of false pregnancy or the agitation associated with estrus, irritable aggression in females is eliminated by spaying. If you worry that your dog will not protect your house after neutering, territorial aggression is not altered by neutering. If your pet is not intended for breeding, neutering is advised to prevent aggressiveness related to sex hormones. Though neutering is not a treatment for aggression, it can help minimize the severity and escalation of aggressiveness and is often the first step toward resolving an aggressive behavior problem. Specific diagnosis of the type of aggression displayed by your pet, identification of the situations that trigger it, and retraining your pet to behave differently are still essential.
Effect on General Temperament
Many pet owners are concerned that a neutered pet will lose its vitality. Basic temperament and intelligence are not altered by neutering. In fact, many undesirable qualities under hormonal influence may resolve after surgery. Your pet will not become less affectionate or playful, nor will it resent you. You will not deprive your pet of any essential experiences. You will, however, be acting as a responsible, informed and loving pet owner. The temperament of females is unlikely to improve after having a litter. Even if you have arranged for good homes for the offspring, pets in a shelter are deprived of adoption. There is no benefit from sexual activity for male or female dogs or cats. Do not project your own physical or emotional needs onto your pet. It is not "unnatural" to control a pet's reproductive activity by having it neutered. Rather, it is unkind not to neuter a pet.
Effect on Escape and Roaming
A neutered pet is less likely to roam. Castrated male dogs and cats tend to patrol smaller outdoor areas and are less likely to engage in territorial conflicts with rivals. Spayed female cats may actually expand the territory patrolled. A pet that has already had successful escapes will not stop running away after it is neutered.
Effect on Inappropriate Elimination
Inappropriate urination and defecation may continue long after the initial cause has passed. Because this behavior is only partly under hormonal control, male or female pets may begin to eliminate inappropriately even after neutering. Neutering an animal that has begun to inappropriately eliminate reduces the urine odor of intact adults and eliminates the contribution of hormonal factors. Unless underlying emotional or physical factors are controlled and environmental reminders are removed, the undesirable behavior may persist beyond neutering.
Effect on Body Weight
Because of metabolic changes that follow neutering, some pets may gain weight. Many pets gain weight after neutering because they are fed more by owners who feel guilty for subjecting their pet to any discomfort. Pets, like people, become less active as they mature and may gain weight. Activity declines as a young pet matures, regardless of whether or not it is neutered. Before the surgery, and particularly for sexually mature individuals, energy is channelled toward reproduction. Females in heat are often agitated and irritable, sleeping and eating less. Males may be more reactive to stimuli in general and more acutely aware of rivals or intruders on their territory. Neutering reduces the intensity of many behavior problems and eliminates or prevents certain types of undesirable behavior. After your pet is neutered, adjust its food intake to prevent excessive weight gain. Weight gain following neutering is easily controlled. If food intake is not decreased after neutering, a gradual weight increase is likely. Suggested quantities on pet food packages are meant as general guidelines. Adjust your pet's food intake according to its physical requirements and appearance. Weight loss requires careful monitoring by your veterinarian, particularly in obese pets. Special weight-reducing diets are available, but rapid weight loss is almost never advisable.
Weight gain is sometimes associated with certain medical disorders. If you believe your pet's weight gain is out of proportion to its food intake and exercise level, consult your veterinarian.