When someone purchases a new puppy they have been conditioned throughout
the years to take the puppy to the vet, get their series of boosters, get
their rabies shot, and then schedule their dog to be neutered. The first
question that I always ask, much to the owners surprise is “Why are you
deciding to castrate your male puppy”? Many times people don’t even have an
answer and reply, “That’s what I thought I was SUPPOSED to do”. Other times
people do provide a reason ranging from health benefits, which I can usually
quickly dispel, to preventing unwanted behavior. In this post I will deal
solely with the behavior modification issue in male dogs. The issue of
behavior modification is far from clear cut and may surprise some people.
Often times people fear that owning an intact male dog in their house will
come with unwanted behavior. Typical behaviors that people associate with
intact male behavior include mounting, straying and wandering from the
homestead, aggression towards humans and towards other dogs, and marking.
Many people feel that neutering their puppy at an early age will prevent
these behaviors from occurring and will make their dogs better pets that are
more suitable for the household. Does this not create the same moral hazard
that declawing a cat to prevent unwanted scratching creates? Many
veterinarians who will not perform declawing for ethical reasons tell owners
that they should not own a cat if they cannot deal with unwanted cat
behaviors like clawing furniture, but they routinely neuter pre-pubescent
dogs to curb other unwanted behaviors. The procedure is just as aggressive
surgically and if done at an early age, comes with many unwanted health
complications that are beyond the scope of this post. In Europe castration
is largely considered tantamount to declawing, tail docking and ear
Putting ethics aside for the moment, what are the
behavioral effects of neutering male dogs? A retrospective study of only 42
dogs studied just that and the results were mixed. The behavior that is best
controlled through neutering is roaming. Castration eliminates this behavior
in 80 to 90% of dogs. Locking your gate would also accomplish the same
thing. Urine marking in the house was controlled in only 50% of dogs and
urine marking around or outside of the house where other dogs had marked was
not affected at all. Mounting of people or other animals was reduced in 67%
of the dogs. Lastly, aggressive behavior was only altered in cases involving
inter-dog aggression and declined in 62% of dogs. Territorial, fear-induced
aggression, and food aggression were not altered in any dogs 1. In another
report dealing with aggressive behavior in dogs, prepubertally castrated
male dogs were just as aggressive as noncastrated dogs 2.
There is at least the potential for some behaviors to
worsen after castration. Testosterone is known to affect anxiety behaviors;
for example, hypogonadal men with lower levels of testosterone are more
likely to suffer from anxiety and depression disorders. Treatment with
testosterone alleviates these symptoms. Preliminary studies in mice were
performed where mice were presented with stressful situations and their
ability to process this fear with both contextual (same environment) and
cued fear (an audible stimulus preceded a shock) were tested before and
after castration. The results were mixed and showed that castration did
inhibit contextual fear memory processing, supporting the fact that the
processing of contextual fear memory within the hippocampus area of the
brain is testosterone dependent. It is established that men tend to develop
post-traumatic stress disrorder less frequently and of a less severe nature
than women due to this inhibition of contextual fear memory inhibition3.
Would it not be reasonable to conclude that it is at
that neutering dogs could increase fear behaviors through inhibition of the
dog’s ability to explore its environment and to process and/or extinguish
fear memories correctly? Renowned behaviorist Parvene Farhoody looked at
this possibility in her Masters thesis at Hunter College in 2010. The study
was based upon a 101 question survey called the Canine Behavior and Research
Questionnaire (C-BARQ) to collect information on 7 different behavioral
characteristics for over 10,000 dogs. Their data showed that neutered dogs
were more aggressive, fearful, excitable and less trainable than
intact dogs 4.
These data were not peer-reviewed or published, but it is my understanding
that they are continuing work in this field and that a larger study’s data
is currently being compiled and will be submitted for review and
publication. A similar C-BARQ questionnaire’s data involving a sample of
over 6000 dogs was compiled and presented to the Third International
Symposium on Non-Surgical Contraceptive Methods for Pet Population Control
and showed neutering to worsen behaviors including: dog-directed fear
aggression (breed dependent), begging for food, fear behavior and
sensitivity to handling, aggression towards people and other dogs, decreased
energy, excessive barking, and rolling in and eating feces5.
Castration may also contribute to the myriad
behavioral issues that arise later in life, grouped under the category of
cognitive dysfunction. Cognitive dysfunction is basically doggy Alzheimers
and signs can include disorientation, housesoiling, aggression, wandering
and confusion. It has been shown that neutered dogs progress much more
rapidly from mild to severe cognitive dysfunction than intact males. The
investigators state, “This finding is in line with current research on the
neuro-protective roles of testosterone and estrogen at the cellular level
and the role of estrogen in preventing Alzheimer’s disease in human females”
One more interesting thing to note is that in behaviors where it is
generally considered that castration can improve behavior (The above data
sheds doubt on even some of those dogmas.) there is no benefit to early
neutering. It has been shown that the improvment of behavior through
castration is not age-dependent. There is no rush to hurry up and “fix” your
dog while he is still growing both physically and mentally. It is important
to choose your puppy wisely. You must consider the inherent energy and
potential for aggressiveness when selecting a breed of dog to join your
family. Proper training, setting of rules and boundaries and exercise is
imperative from day one. If problematic behaviors arise you must identify
and work to rectify them quickly before they become habitual, and it is
imperative to utilize the services of a behaviorist and/or trainer when
problems arise. Castration should be considered as a last resort and
expectations for its success should be reasonable. Castration should not be
performed on a pre-pubescent dog as testosterone is vital for skeletal and
et. al. Castration of Adult Male Dogs: Effets on Roaming, Aggression, Urine
Marking, and Mounting. J Am Vet Med Assoc 1976; 168: 1108-10.
B.J.: Copulator and Aggressive Behavior in the Prepubertally Castrated Dog.
Horm Behav, 1, (1970): 127-36.
C. Role of gonadal hormones in anxiety and fear memory formation and
inhibition in male mice. Phsiol Behav. 2012. 105 (5). 1168-74
Behavioral and Physical Effects of Spaying and Neutering Domestic Dogs.
Smmary of findings detailed in Masters thesis submitted to and accepted by
Hunter College in May 2010.
5. Duffy, D.
et al. Non-reproductive Effects of Spaying and Neutering on Behavior in
Dogs. Power Point presentation to the Third International Symposium on
Non-surgical Contraceptive Methods for Pet Population Control.
6. Hart BC.
Effect of gonadectomy on subsequent development of age related cognitive
impairment in dogs. J Am Vet Med Assoc. 2001 July 1; 219 (1) 51-6.