Over the years, I've heard a lot of people/organizations that have claimed that people should alter their pets for a whole host of reasons. Generally, among the reasons listed is that it will make your pet less aggressive (this information is also sometimes used to justify laws mandating the spay/neuter of certain breeds/types of dogs).
While certainly there are a lot of good reasons to spay/neuter your pet (ease of population control being an important one), are the statements about improved behavior one of those?
Fortunately, there has been some research done on this topic. This research is not terribly new (the study was performed in 2006) but it has been sitting in my inbox to discuss for awhile and I've just never made the time to discuss it.
The research was done by Dr. Deborah Duffy and Dr. James Serpell, both at the School of Veterinary Medicine at the University of Pennsylvania. Both were also involved in a paper about aggression as it relates to breeds of dogs that I discussed a couple of years ago.
In the effects of spay/neuter study, they interviewed more than 1500 dog owners (all breed club members with dogs of known heritage) with dogs over the age of 1 year old. They had a 50/50 male/female ratio and 40% of the dogs were either spayed or neutered. In the interviews, the asked the dog owners to fill out the C-BARQ scorecard on a variety of different behavioral problems including:
- Stranger directed aggression
- Owner-directed aggression
- Dog-directed fear/aggression
- Dog Rivarlry
- Stranger-directed fear
- Nonsocial fear
- Separation-related behavior
- Touch snesitivity
Dogs from 11 different breeds were included - ranging in size from Yorkies to Rottweilers to measure differences among breeds.
The #1 reason people said they altered their pets was because of birth control (42%). But interestingly, 31% said to prevent health problems and 18% noted to control/prevent behavior problems. So behavior modification is a major driver why people alter their pets.
The results of the research may surprise you.
Spayed females were more aggressive toward both strangers and owners than intact females.
Spayed females were more fearful and sensitive to touch than their intact counterparts.
Neutered males were much less likely to mark their territories.
Both males and females that were altered were more likely to beg for food and to engage in excessive licking of people or objects.
The incidence of dog-directed fear/aggression varied quite a bit by breed. Some breeds: Bassett Hounds, English Springer Spaniels, Dachsunds, Labrador Retrivers and Yorkshire Terriers showed more aggression after being altered, where Golden Retrievers, Poodles, Shetland Sheepdogs, Rottweilers, Siberian Huskies and West Highland Terriers were either just as likely, or less likely to have shown aggression toward other dogs when altered.
In a second study, the researchers used a convenience sample of more than 3500 dog owners (76% of which were spayed or neutered) and measured the same criteria.
In this study, dogs of both genders were more likely to show dog-directed aggression/fear or owner-directed aggression when altered.
Dogs of both genders were also more likely to have touch sensitivity and non-social fear when altered.
Altered dogs were also likely to be less energetic.
Interestingly, for one breed-specific group in this survey, Doberman Pinchers, altered females were much more likely to show stranger-directed aggression, but altered males were much less likely to show stranger-directed aggression.
It should be specifically noted, that in all cases, the vast majority of all dogs studied showed no forms of aggression at all, regardless of their intact status -- and that differences in the scores don't mean that either situation results in severe behavioral problems.
In conclusion, the researchers report that for most behaviors, spaying/neutering was associated with worse behavior, contrary to popular wisdom, although a few behaviors (energy level, urine marking) were reduced with spay/neuter.
The effects of spaying/neutering were often specific to certain breeds, and not always equivalent between sexes.
You can see an overview of the study, along with a powerpoint presentation with specific details on the study here. (Note, I have not been able to obtain the complete study, so all of my reporting on this above is based on the powerpoint presentation attached).
I'm posting this information for a lot of reasons. I think there is a lot of "conventional wisdom'" that exists in animal welfare circles that has shown to not actually be grownded in actual data and I agree with the researcher's conclusions that if pet owners have a more accurate expectation of possible impacts of spay/neuter surgery they will be better equipped to prevent negative behaviors.
I also think it's interesting to read this in a world where many people want to link intact status to aggression and a reason for major dog bites. This may be true in at least some cases in male dogs, but definitely not for female dogs.
I also like their conclusion that similar research should be done with other proceedures similar to spay/neuter (like tubal ligation and vasectomies) to see if those can create the desired results (ease of population control) without the possible negative impact of lost hormones.
Does this change the way we promote spaying/neutering as a form of population control? Should it? Does it change whether or not cities should try to make laws mandating spay/neuter for public safety (certainly, there is no support for this in this research, in addition to the reality that it doesn't work to control population)? Certainly population management is essential to rescue success....but are there better solutions?
Addendum: I should have also noted on this study (and it was wisely pointed out below) that the study is not neccesarily a causal study because all of the other factors were not isolated. So the study does just measure a correlation between spay/neuter and behavior types -- that is not necessarily causal. There is also the issue of whatever variable that comes with owners defining the behaviors vs scientifically defining the behaviors. That said, I do think the study is interesting at the very least...