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To Neuter or Not to Neuter and if so When?

Updated: Jun 14, 2022

Neutering dogs is somewhat of a volatile topic with some strongly opposing views displayed for both sides of the argument. Most large rescue organisation neuter dogs in their care as a matter of course seeing it as the responsible thing to do (which in some cases not doubt it can be) but in some cases it is not. I am aware of a situation where an un-neutered elderly dog of some 14 years of age (somewhat past his ‘sell by date’) found himself due to the loss of his owner in a well known rescue who required him to be neutered before being despatched to his new home. When this practice was questioned by the proposed new owner as unnecessary and at his age potentially risky, it was simply stated to be ‘standard practice’.

I do not believe for the reasons set out below that neutering any dog should be ‘standard practice.’ Each dog owner needs to consider carefully their reasons for wishing have their dog neutered. Once they have done so I recommend that they then consider and take account of the current research and also consider whether they should take professional advice (from a vet or behaviourist as appropriate, who is familiar with such research (as not all are)) before making a decision as to if and indeed when (if a decision is made to do so) to neuter. My beliefs and opinions are based on the review of a substantive number of what are generally considered sound scientific studys (see references below).

Advantages of Neutering Your Dog

Male Dogs

  • A reduction in inter-male only dog on dog aggression (this is a very specific behavior and not related to but commonly confused with nervous aggression – neutering will NOT help nervous aggression it will generally make it worse).

  • A reduction in male ‘wanderlust’ especially in search of females in heat

  • Prevention of testicular or prostate cancer

  • Less ‘humping’ behavior

Female Dogs

  • Reduction in the likelihood of mammary gland cancers and prevention of uterine pyometra

  • No messy oestrus cycle (and amorous followers)

  • No unwanted pregnancies

I would suggest that most responsible pet owner are likely to be able to avoid unwanted pregnancies as we do not let our dogs run loose, a we did in the 1960’s and 70’s. In relation to the reduction in the risk of various cancers – the above do not appear to be common cancers and the increased risk is not significant. 5. Would you resort to preventative surgery ‘just in case’ if you did not have a high risk of developing a specific cancer? *Pre Pubescent Puppies

I cannot readily think of any advantage other than the small risk of a bitch getting ‘caught’ on her first oestrus being removed. A medical advantage from a vetinary perspective may be quicker recovery period, ease of handling and of course no obesity issues to complicate matters! What you are doing of course is ensuring that the normal course of puberty and all the natural hormonal changes are curtailed and this will undoubtedly effect the puppies physical and emotional development.

Disadvantages of Neutering your Dog

  • Increased risk of hypothyroidism1.

  • Increased risk of orthopaedic disorders such as arthritis2.

  • Increased risk of incontinence and urinary tract infections (spayed females only)3.

  • Weight gain and subsequent increase in risk of diabetes (the study referenced here relates to cats as there appears to be no similar study of dogs, but like humans, obesity increases the risk of diabetes and there is no reason to think that the risk is less in dogs)4.

  • Potential earlier mental decline5.

Pre Pubescent Puppies

  • Increased risk of bone disorders6.

  • Increased risk of crucia Ligament tears7.

  • Increased risk of bone cancer in large and giant breeds8.

Behavioural Reasons for Neutering

If you wish to neuter for behavioural reasons – you may wish to be certain that the cause of behaviour you wish to curtail has been correctly identified and if so what are the percentage chances (if any) of neutering improving or curtailing this behaviour. If you get it wrong the behaviour could be made worse! A substantive (in numbers) and I believe generally accepted as scientifically sound C-BARQ study undertaken in 2006 on the effects of neutering on canine behaviour9. (‘the 2006 Study’) and a subsequent masters thesis on the same subject10. ‘the 2010 thesis’), show some perhaps surprising results. For a quick read these have been summarised by Stanley Coren PHD, a world renowned psychologist in his article for Psychology Today ‘Are There Behaviour Changes When Dogs Are Spayed or Neutered? Spaying or neutering dogs can cause unexpected and unwanted behaviour changes.’ Posted on 22 February 2017.

An even more recent C-BARQ study in 201811. again confirmed that the previous generally accepted view that neutering should improve aggression issues in males appeared to be incorrect and to the contrary it is often likely to increase it in many (but not all) circumstances. Again Stanley Coren has provided a useful summary and his opinion on the subject in his article in Psychology Today ‘Neutering cases Behavioural Problems in Male Dogs’ dated 9 May 2018. I would add however regarding any article on the subject that they of course indicate an individual analysis and point of view, the studies themselves are balanced and impartial. I do not intend to regurgitate the contents of these studies or articles here as to do so is beyond the scope of this short article. I would however suggest that they are worth reviewing. I will however summarise a few important points.

Given the main behavioural related reason people neuter male dogs is generally to curtail aggression the results of the 2006 Study and the 2010 thesis may be quite surprising to many in that they indicated neutering more often has the opposite effect. There are however still circumstances where it could be beneficial, but you need to ensure the cause of the behaviour is accurately identified in the first instance, which too often it is not.

Spayed females and neutered dogs both in general show increased aggression after neutering. This is however dependant upon the cause of the aggression, hence the importance of this being correctly identified. Nervous aggression (which is the most common form of aggression) is likely to be worsened by neutering whilst dominance aggression (often displayed male to male (but substantively less common and often mis-diagnosed)) can be reduced . More often than not however, aggression is fear based and will not be improved by neutering. Simply put this is because the hormone testorone produced by 'intact' males increases confidence, the lack of which in a nervous dog displaying aggression simply increases the problem.

In terms of female aggression overall this is markedly increased post neutering as opposed to male aggression and even more so if they are neutered before they are a year old. Notably these studies indicated an overall 31% increase in fearfulness (the main cause of aggression issues) in all dogs post neutering and a 33% increase in touch sensitivity (another obvious cause of aggression). These studies also indicated an overall increase in excitability and less trainability in neutered dogs (albeit in my experience I have in a number of cases seen descreased excitability, but this does not always increase the facilitation of training)!

Interestingly whilst neutering is still very much considered ‘the norm in the UK’ this is less so in Europe and indeed I understand that in Norway it is illegal to neuter dogs unless there is a medical reason to do so!

A word of caution! Each dog is an individual and no two cases in terms of behavioural issues are the same. If you are considering spaying for behavioural reasons you would be well advised to seek the advice of your vet to check for any underlying medical issues and if this cause is discounted it is advisable to seek the advice of a suitably qualified/experienced canine behaviourist.

Summary This short article is a very concise summary of my overview of the current science I have identified and considered . I am not implying that this is the only information you may wish to consider. I am not a vet and I am not medically qualified, I am howevere Certified Canien Behaviourist and have first hand experience of many dogs pre and post neuture and spay.

I hope that this article prompts some initial thoughts and encourages you to undertake further research (and perhaps review some of the studies referenced here) before making a decision regarding neutering. There is a lot of information out on the web from reliable and sound sources. I would encourage you to carry out some research and take unbiased professional advice before making a decision. You are then most likely, if you do decide to neuter your dog to obtain the results you expected. You may also be glad that you decided not to! *(Puberty varies from breed to breed and between the sexes – check with your vet/breeder)

References:- 1.



3. 4. 5.





9. Deborah L. Duffy and James A. Serpell , ‘Non-reproductive effects of

spaying and neutering on behaviour in dogs’

10. Parvene Farhoody (‘the 2010 thesis’) ‘Behavioural and Physical Effects

of Spaying and Neutering Domestic Dogs (Canis familiaris)’ ‘. submitted

to and accepted by Hunter College

11. McGreevy PD, Wilson B, Starling MJ, Serpell JA (2018) Behavioural risks in

male dogs with minimal lifetime exposure to gonadal hormones may

complicate population-control benefits of desexing. PLoS ONE 13(5):


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