Dogs get their testicles removed primarily to prevent unwanted breeding, reduce the risk of certain diseases, and address hormone-driven behaviors like roaming and mounting. The surgery, called neutering or castration, is one of the most common veterinary procedures performed worldwide and has been a cornerstone of pet population control since the 1970s.
Preventing Unwanted Litters
The single biggest reason veterinarians and animal welfare organizations promote neutering is population control. Spay and neuter campaigns began in the 1960s after growing awareness of the millions of stray and unwanted dogs ending up in shelters each year. Low-cost spay and neuter clinics expanded rapidly through the 1970s and remain a key tool for reducing shelter intake today. A single intact male dog that escapes or roams can father dozens of puppies in a short period, so neutering even one dog has an outsized effect on preventing homeless animals.
Disease Prevention
Removing the testicles eliminates the possibility of testicular tumors entirely, which is especially important for dogs with undescended testicles (a condition called cryptorchidism) since those retained testicles carry a much higher cancer risk. Neutering also prevents benign prostatic hyperplasia, a non-cancerous enlargement of the prostate gland that affects roughly 80% of intact male dogs by age six and 95% by age nine. An enlarged prostate can cause difficulty urinating, straining to defecate, and bloody discharge.
Neutering also prevents perianal adenomas, hormone-dependent tumors that grow around the anus in intact males. Less than 1% of neutered males in one large study had any reproductive health problem reported, compared to 7% of intact males.
There is one notable tradeoff: while neutering prevents benign prostate enlargement, it may slightly increase the risk of prostate cancer (a different and far less common condition). The overall balance still favors neutering for most dogs, but it’s worth discussing with your vet if your dog’s breed has elevated cancer risks.
Behavioral Reasons
Many owners choose to neuter their dog hoping to curb behaviors driven by testosterone: roaming to find females in heat, mounting other dogs or people, urine marking indoors, and aggression toward other males. These are among the most frequently cited reasons for the procedure.
The reality is more complicated than many people expect. Some hormone-driven behaviors do decrease after neutering, particularly roaming and mounting, since those are closely tied to the drive to reproduce. However, recent research paints a more nuanced picture when it comes to aggression. A 2024 study of mixed-breed male dogs found that neutered males actually showed significantly more general aggression than intact males. More neutered dogs also displayed aggression on walks and aggression toward other dogs compared to their intact counterparts. These findings align with several earlier studies.
This doesn’t mean neutering causes aggression. Dogs are often neutered because they already show problem behaviors, which skews the data. It does mean that neutering alone is unlikely to fix an aggression problem, and behavioral training matters far more than surgical status for most unwanted behaviors.
Timing Matters, Especially for Larger Dogs
When a dog is neutered can be just as important as whether he’s neutered. Current veterinary guidelines recommend different timelines based on the dog’s expected adult weight:
- Dogs under 44 pounds (20 kg): Can generally be neutered from six months of age without increased risk of joint problems.
- Dogs 44 to 88 pounds (20 to 40 kg): Waiting until at least 12 months of age reduces the risk of joint disorders like hip dysplasia, elbow dysplasia, and cruciate ligament tears.
- Dogs over 88 pounds (40 kg): Waiting until 24 months may be best to allow full skeletal development before removing the hormones that help bones and joints mature properly.
Research from UC Davis confirmed that mixed-breed dogs weighing more than 44 pounds had a higher risk of joint disorders when neutered before one year of age. Dogs under 43 pounds showed no increased joint risk regardless of when they were neutered. Interestingly, the same study found no increased cancer risk in any weight category for neutered mixed-breed dogs compared to intact dogs.
What Recovery Looks Like
Neutering is a routine outpatient surgery. Most dogs go home the same day. In the first 24 hours, your dog may be groggy, wobbly, nauseous, or more vocal than usual. It can take up to 48 hours for their appetite to return to normal. Gentle movement around the house during this period actually helps recovery; letting them sleep for hours uninterrupted can slow things down.
The critical recovery window is 10 to 14 days. During this time, your dog needs to avoid running, jumping, and rough play. Strenuous activity can cause swelling around the incision, dissolve the stitches prematurely, or open the wound. Your vet will likely send your dog home with a cone collar (the classic “cone of shame”) to prevent licking, which is one of the most common causes of infection or the incision reopening. A small amount of redness, swelling, or even minor bloody discharge from the incision site is normal in the first few days.
Alternatives to Full Removal
Some owners prefer a vasectomy, which sterilizes the dog without removing the testicles. This prevents reproduction while preserving testosterone production, meaning the dog keeps the hormonal benefits for bone and joint development. Vasectomized dogs still carry the risks that come with intact hormone levels, including benign prostate enlargement and perianal tumors. They also retain hormone-driven behaviors like roaming and marking. Vasectomy is far less commonly performed and not all veterinary clinics offer it, but it’s an option worth knowing about if you want to prevent breeding while keeping your dog hormonally intact.