The behavioural effects of castrating male dogs (Neutering)

Having your dog neutered is not a decision that you should take lightly, after all there is no going back once the deed is done! Before proceeding you should consider the effects that castration may have on your dog’s behaviour.

The castration of male dogs will stop the production of the hormone testosterone. This might be beneficial when treating unwanted behaviours that are more likely in males than in females. Urine marking, roaming away from home to track down bitches in heat, inappropriate sexual behaviour, and inter-male competitive behaviour. In contrast, and contrary to popular belief, castration does not “calm a dog down”, since excitable and unruly behaviours are seldom influenced by testosterone.

Testosterone and aggression

Testosterone tends to lower thresholds for aggression, making aggression more likely. It can also make aggression more intense and longer lasting. Thus entire males may be more likely than neutered dogs to respond aggressively in situations where they are feeling threatened or frustrated. Some dogs will behave less aggressively once testosterone levels drop following castration. But the confounding issue here is that testosterone may also act as a confidence booster, and in some cases its absence after castration may mean a dog becomes more brittle emotionally, and more likely to react aggressively when feeling under threat.


Testosterone is often not the entire story (Pun intended)

It is important to note that while testosterone can influence some types of unwanted behaviour, there are normally other factors at play, such as a dog’s environment, prior learning, masculinisation of the brain before birth and during puberty, and the individual emotional and behavioural tendencies of the dog. As a result, even if an unwanted behaviour is influenced by testosterone, castration may not be the easy fix many hope that it will be. For the reasons outlined above I personally believe that castration should be the last option on the table, not the first.