Common misconceptions of neutering
It is widely – and falsely – believed that neutering “calms a dog down”. However, an adult or adolescent dog’s basic temperament is relatively independent of testosterone, and neutering won’t make any significant changes to his intelligence or personality. What it can do is affect his emotional state, and what behavioural options occur to him.
The use of surgical neutering is widespread, utilised for its health benefits (Forsee et al., 2013; Yates and Leedham, 2019), reducing sexually dimorphic behaviours (Downes et al., 2015) and unwanted behaviours (Roulaux et al., 2020), and population control (Wongsaengchan and McKeegan, 2019). Challenges arise around appropriate neutering age, individual clinical cases and sex of the dog (Diesel et al., 2010). The UK is reported to have the highest worldwide neutering rate (Heimendahl, 2010), with the 2021 PAW Report informing that 71 percent of the canine population has been neutered, despite this decreasing from 81 percent in 2017. Conversely, in many Northern European countries ovariohysterectomy and castration procedures are monitored and are even prohibited in some locations by animal welfare acts (Heimendahl, 2010).
Current links between neutering and behaviour are conflicting, with anecdotal evidence valuing routine neutering for modifying behaviour, emphasising that neutering will improve behaviour, producing a calmer, well-rounded individual. Scientific literature fails to create a coherent, convincing argument, with many studies evidencing positive, negative or minimal impact of neutering on overall behaviour.
Due to conflicting evidence surrounding the effects of gonadectomy on unwanted behaviours, it is suggested that clinicians consider individual clinical and behavioural history, and discuss potential behavioural benefits and contraindications with the owner prior to the procedure. It may be prudent to trial temporary medical contraceptives in dogs with behavioural issues, particularly fearfulness, and evaluate the effect of reducing testosterone and oestrogen on overall behaviour, before opting for permanent removal of reproductive hormones.
Links between neutering and anxious behaviour appear more conclusive and consistent than aggression, with published evidence suggesting neutering is not an appropriate strategy for reducing anxious responses and may magnify anxious and fearful tendencies.
To further existing understanding, research needs to encompass behavioural evaluation of dogs pre- and post-neutering, which poses ethical issues if surgical gonadectomy may perpetuate existing behavioural issues.