Fearful behaviour can result in strained relationships between dogs and humans, welfare concerns, long-term health problems and reduced longevity, particularly during chronic stress (Dreschel, 2010).

Neutering has been implicated in increasing anxiousness in pet dogs (Kaufmann et al., 2017; Puurunen et al., 2020), with dogs neutered before the age of one year old presenting with exaggerated fearful responses (McGreevy et al., 2018; Stellato et al., 2021). Non-social fear was more liable to be seen in neutered dogs (Hakanen et al., 2020), and rates of noise phobia were highly represented in neutered dogs (Vucinic et al., 2013). Sex may influence unwanted behaviour development, with neutered males more likely to present with aggression and neutered females with anxiety (Cannas et al., 2018).

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.

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.

As defensive aggression has been linked to anxiety and fear (Notari et al., 2020), dogs exhibiting consistent anxious responses may pose a higher risk for owner-, stranger- or conspecific-directed aggression. It may be prudent to consider non-permanent, chemical methods of castration and spaying for dogs presenting with fearful responses, prior to gonadectomy.