The neutering of dogs and bitches is considered for a number of reasons. Apart from population control, these include the avoidance of the inconvenience of unwanted seasons in bitches and the reduction of risk or total prevention of medical conditions in later life. The latter includes mammary and testicular cancer and pyometra, a potentially fatal uterus infection. The validity of some of the medical benefits has been questioned but the prevailing opinion is that the benefits outweigh any concerns in most cases, even the increased risk of incontinence in older bitches. Neutering is also carried out as a means of curing or preventing behavioral problems.
It remains a common misconception that the castration is a universal remedy for behavior problems. Although it can help to cure problems and early castration can prevent the development of problems, the procedure is only relevant to certain types of behavior. The behaviors most likely to be affected are those that are sexually dimorphic, that is, they are behaviors that are more common in or specific to male dogs.
Males exhibit behaviors that are influenced by testosterone, such as scent marking, roaming away from home to find potential mates, inappropriate sexual behavior and aggression specifically directed towards other male dogs. It has been suggested that the male hormone, testosterone, plays a part by increasing reactivity and maintaining it for longer in dogs that have not been neutered than dogs that have. This may help to explain why males that have not been neutered show some types of aggression, that does not involve other males, more often than neutered males and females. This does not include aggression categorized as involving fear or territorial aggression, which makes sense because it is often related to fear. It has also been suggested that fear related behavior may be made worse by castration because testosterone helps to maintain confidence.
When relevant, there is only a percentage chance that castration will work. This varies from 90% for some problems, such as roaming to find potential mates, down to 50% for others such as inappropriate scent marking in the home. This is because the male brain is programmed to display male behavior by testosterone as it develops and those behaviors can continue because of this of this and learning that occurs prior to castration. So if neutering is carried out, behavior modification therapy is also required to address the learnt components of the problem. Where castration does result in improvement the results can be rapid or gradual. For example one piece of research showed that roaming to find potential mates improved within two weeks in 44% of dogs and within six months for 50%. Perhaps this is a further indication of the need to address the learnt component of a behavior because testosterone is out of the system within 6 to 24 hours.

As far as behavior problems are concerned, the spaying of bitches appears to be relevant if aggression occurs before and when the bitch is in season, she is showing signs of false pregnancy or is at the stage in her cycle, real or false, when she would be feeding puppies. Likely problems include the adoption and guarding of items as surrogate puppies, nest building and the onset of aggression in defense of it or other items she treats as resources. I have listed the stages because they are associated with different stages of hormone influence.
It has been suggested that neutering will not necessarily remove aggression associated with a bitch’s cycle and that problems may continue for two or three cycles after neutering. This is feasible because mechanisms, other than those the ovaries are responsible for, occur at the time of oestrous. Exactly what internal mechanisms are responsible for cyclical behavior changes after neutering has yet to be proved but hormones that are released from the brain to trigger the cycle are a possibility. It is also suggested that eventually the cycling stops because the ovaries are not there to send feedback messages.
What has been shown in research is that bitches that are spayed are more likely to show what the researchers called ‘dominance aggression’ than those that have not been spayed. It is important to note that this trend was most significant when comparing groups of bitches spayed under six months of age that had already been showing aggression. This seems to be consistent with other claims that bitches that have been neutered can show masculinized behavior. The researchers’ suggestion is that behavior problems involving aggression should be addressed before neutering is carried out. They also stated that the neutering of bitches should not be considered as a means of addressing behavioral problems, except those directly related to the cycle of their seasons including, one assumes, the competitive behaviors described above.

© David Appleby 2001
Also see: The Behavioural Effects of Canine Castration by Hazel Palmer

Return to Article Titles Page>>>

Please note that techniques are advised upon in good faith and no liability can be held in the event of damage or injury to persons, property or animals as a result of correct or incorrect implementation of the techniques described.