Dog Behavior and Training: Neutering and Behavior

By Monique Feyrecilde, BA, LVT, VTS (Behavior); Debra Horwitz, DVM, DACVB; Gary Landsberg, DVM, DACVB, DECAWBM

Why is neutering dogs recommended?

Many male animals are neutered (castrated) as a best practice for health and handling. Castration is often considered part of responsible pet ownership. Much research has been done about the health and behavioral impacts of castration in pet dogs.

Pet overpopulation is a global concern and unplanned litters account for a staggering number of euthanasias in the United States and around the world. Preventing unplanned litters is a crucial part of responsible pet ownership. Castration is one way to prevent unplanned litters, although the timing of this procedure has come under more scrutiny within the veterinary science community in recent years.

What is involved in neutering a dog?

Neutering, or castration, is the surgical removal of the testicles. Removing the testicles removes the primary source of testosterone in the body, resulting in changes in sex drive, hormone-related behaviors, and hormone-related health concerns. Removing the testicles can also protect against some later-life health concerns, such as testicular cancer and prostate enlargement, as well as hormone-related tumors of the perineum. Neutering may also be associated with an increased risk of some musculoskeletal disorders and cancers, when done before a given age.

When should my dog be neutered?

All dogs are not physiologically the same. Different breeds and sizes of dogs have different optimal ages for castration. According to a recent study, veterinarians and pet owners should work together to discuss the optimal age of neutering, instead of following a blanket age recommendation. Every dog owner should consult with their veterinarian about the health impacts of castration for their individual dog.

"Different breeds and sizes of dogs have different optimal ages for castration."

Historically, veterinarians have recommended neutering dogs before puberty. This not only minimizes the risk of unplanned litters, but also may offer behavioral benefits. Puberty and adolescence are the time when animals transition from youth to sexual maturity. In most breeds and sizes of dog, this period spans from 6 months to 2 years of age. Hormone surges during puberty can and do influence the behavior of any individual. Ask the parent of any teenager! If you are considering waiting until social or structural maturity before neutering, be sure to talk to your veterinarian in-depth about what to expect with respect to your dog’s needs for exercise, training, appropriate and safe confinement, and appropriate social environments.

What are the impacts of neutering on dog behavior?

The best predictors of a dog’s behavior are his genetic background combined with the social learning and training he receives. Reproductive status does play a role in behavior, but it is not the dominant influence over animal behavior.

Testosterone influences sex drive and sexual acts, searching for mates, territorial behavior such as urine marking, and aggression between males. Testosterone may also affect confidence and the role of the experience of fear in some dogs. Neutering will result in a reduction in sexual behaviors (breeding attempts and masturbation), seeking mating opportunities, and urine marking. Some of these sexual behaviors can be dangerous, resulting in fights between dogs, roaming and being injured by cars, fences, poisons, and other threats, and neutering will decrease these risks.

"Reproductive status does play a role in behavior, but it is not the dominant influence over animal behavior."

There is conflicting evidence at this time, but it is possible that neutering males before puberty may correlate with increased aggression directed toward strangers and strange dogs. However, further research is needed before any firm conclusions can be drawn in this situation. Neutering was historically considered a crucial part of therapy for all dogs displaying unwanted aggression. A more careful examination of the aggression with a veterinarian experienced in treating behavior disorders is now recommended prior to neutering, as neutering may worsen fear-related behaviors in a small subset of dogs.

Is there an alternative to neutering my dog?

Dogs can also be sterilized using vasectomy. In dogs for which castration at any age may be associated with adverse health risks, vasectomy is an excellent alternative to prevent unplanned litters and continue to control the pet overpopulation epidemic.

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