Gonadectomy Status and Aggression in Dogs


A recent study examined the age-old question: Are neutered dogs more or less likely to be aggressive?

Gonadectomy has historically been recommended as a modification method for behavioral issues in both male and female dogs; however, existing literature provides conflicting information on this method’s level of benefit.

According to the authors of a recent article published in Frontiers in Veterinary Science, “every prospective, controlled study that examined the effects of gonadectomy on the aggressive behavior of dogs demonstrated either no change in aggressive behavior or an increase in aggressive behavior after gonadectomy.”


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The authors examined the relationship between canine gonadectomy and aggression toward familiar people, strangers, and other dogs. Multiple age classes of dogs were examined using a validated behavioral questionnaire known as the Canine Behavioral Assessment and Research Questionnaire (C-BARQ).

Study Design

Developed by researchers at the University of Pennsylvania, the C-BARQ is used to assess canine behavior and temperament and can evaluate dogs in preparation for service and guide work. The survey is available online for owners to complete and includes 26 questions related to aggression toward familiar humans, strangers, and other dogs. Questions address various forms of aggressive behavior, including food and toy guarding, behavior toward children, and lunging or barking at others while leashed or in the car.

Owner responses to the questionnaire were compiled and examined. The major variables examined were gonadectomy vs intact status and age at gonadectomy.

Dog ages were categorized as follows:

  • puppy (6 weeks to 6 months)
  • juvenile (7 to 12 months)
  • adolescent (13 to 18 months)
  • adult (more than 18 months)

Survey responses were excluded from the study if signalment or health history information was incomplete or if gonadectomy was performed either before 6 weeks of age or to correct a behavioral problem. Answer scores ranging from 0 to 4 categorized aggression level as none, mild, moderate, or severe.


C-BARQ questionnaires from 15,370 dog owners completed between 2004 and 2011 were included in the study. Of the responses, 13,795 (89.7%) reported some level of aggression toward familiar people, 13,498 (87.8%) toward strangers, and 13,237 (86.1%) toward other dogs.

The authors determined that gonadectomy status generally had no effect on aggressive behavior toward familiar people, strangers, or other animals. Similarly, the age at which gonadectomy was performed had no significant relationship with aggressive behavior. However, the authors found that gonadectomy during the juvenile (7 to 12 month) stage correlated with a low but significant (22%) increase in moderate or severe aggression toward strangers compared to aggression levels in intact dogs.

Take-home Message

According to the results of this study, intact dogs are not more likely to display aggression toward humans or other dogs, and gonadectomy is not protective against aggressive behavior. The authors emphasized that canine aggression is likely influenced by a complex combination of factors, including genetics, owner behavior (eg, level of training and a history of neglect or abuse), lifestyle (isolation vs socialization), and medical issues.

Dr. Stilwell received her DVM from Auburn University, followed by an MS in Fisheries and Aquatic Sciences and a PhD in Veterinary Medical Sciences from the University of Florida. She provides freelance medical writing and aquatic veterinary consulting services through her business, Seastar Communications and Consulting.

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