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The Surprising Link Between Dog Size and Behavior

Analysis by Dr. Karen Shaw Becker

link between dog size and behavior

Story at-a-glance -

  • University researchers in Budapest conducted a study to determine if dogs know how big they are
  • The research team concluded, based on the dogs’ behavior in approaching three different-sized wall openings, that they do in fact understand their own body size
  • Common canine experiences also give dogs information about their body size; in addition, there are training classes that teach dogs better body awareness
  • An earlier University of Sydney study concluded that body size plays an important role in dog behavior

Do dogs know how big they are? At first glance it would seem they don't, since many of us have known or at least heard of Great Dane lapdogs or feisty Chihuahuas who routinely challenge dogs several times their size to "step outside." Based on these and similar observations, it's a bit of a mystery as to whether our canine companions are aware of their size.

Recently, a team of Hungarian scientists attempted to answer this question and published the results of their research in the journal Animal Cognition.1

Results Suggest That Yes, Dogs Comprehend Their Body Size

The researchers, all from the Department of Ethology, Institute of Biology, Eötvös Loránd University in Budapest, conducted their study based on the assumption that if dogs understand the size of their bodies, then they'll respond differently to different sized wall openings.

The dogs were presented with three size openings — smaller than their body, about the same size as their body, and larger than their body — and their responses were timed. The researchers observed that the dogs were slower to approach a too-small opening than a larger one. When it came to approaching openings they could fit through, if a bit snugly, their time fell somewhere between the times it took them to approach the too-small and plenty-large openings.

The researchers concluded their study results "convincingly assume that dogs can represent their own body size in novel contexts."

Dogs May Also Learn Their Body Size Through Experience

Certified animal behaviorist Karen London agrees with the researchers' conclusion but believes there are other explanations for the dogs' behavior as well, including that they may have learned through common canine experiences what they can and can't fit through.

"The results of the experiment may simply reflect some generalization by dogs from a lifetime of experience," London writes in Bark magazine. "In other words, I'm not convinced that this experiment shows what the researchers think it does. Even though the results of the research are consistent with such an awareness, they do not disprove other possible explanations.

Dogs have a lot of experience moving around in the world and going through or between things. Perhaps what this experiment shows is that they are capable of determining what they won't fit through, which might simply mean they can see that objects and gaps are different sizes."2

London, who is also a certified dog trainer, makes the point that there are many classes designed to teach dogs better body awareness, especially dogs who compete in agility.

"By practicing a variety of skills — walking backward, weaving through a person's legs, crawling forward and backward, putting front or back paws on a platform and walking backward up a stair or two — dogs improve their ability to coordinate their own movements in a variety of situations," London explains.

Body Size Plays an Important Role in Canine Behavior

A 2013 study by researchers at the University of Sydney suggests that a dog's size and the shape of his skull play a significant role in his behavior.3 The research team used the Canine Behavioral Assessment and Research Questionnaire (C-BARQ) as a data-gathering tool, analyzed information for over 8,300 dogs of 80 different breeds, and compared them to the shape of 960 dogs of those breeds.

Their results revealed a strong association between height, bodyweight, skull proportions (width and length), and behavior and concluded that smaller dogs show more aggression than their larger counterparts.

" … our research shows that certain physical characteristics in dogs are consistently associated with certain types of behavior," lead study author Dr. Paul McGreevy of the University of Sydney's Faculty of Veterinary Science told "Essentially, the shorter the dogs the less controllable their behavior is for their owners."4

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Over 90% of Undesirable Behaviors Were Size-Related

The researchers found that as the height of the dogs decreased, there was an increase in the incidence of mounting behavior, owner-directed aggression, begging for food, and attention-seeking. In contrast, increasing height was associated with trainability. Another finding: when average bodyweight decreased, excitability and hyperactivity increased.

The study revealed that 33 out of 36 undesirable behaviors were associated with a dog's height, bodyweight, and skull shape. Some of these behaviors included:

Begging for food

Urine marking

Fear of other dogs

Peeing or pooping when left alone

Non-social fear

Separation anxiety


Sensitivity to being touched

Mounting people or objects

Aggression toward owner

Another interesting insight from the study was that while long-skulled dogs (e.g., Afghans, Salukis, and Whippets) excel at hunting and chasing behaviors, they also tend to display certain negative behaviors, including fear of strangers, persistent barking, and stealing food.

"Given hunting dogs have not traditionally been companion animals sharing close quarters," said McGreevy, "this may not be surprising."

Short-skulled dogs like the Pug and Boxer — breeds that have undergone, and in many cases suffered generations of selective breeding to further "enhance" their pushed-in faces — tend to display more puppy-like behaviors as adults. They also seem to have completely abandoned many of their hunting instincts.

Additional Observations From the Study

Unwanted behaviors increase as the size and height of a dog decrease.

Dogs with short muzzles engage in more grooming and compulsive staring.

Smaller breeds, especially terriers, showed more stranger-directed aggression. The researchers wonder if terriers were selected for aggressiveness because their job at one time was to chase and hunt underground prey. It could be that smaller breeds with short legs have inherited aggression.

Smaller dogs engage in more attention-seeking behaviors — which are linked to jealousy and territorialism — during times when their owner is paying attention to someone else.

Larger breeds descended from smaller breeds that were meant as companion dogs may have behaviors that are at odds with their body size.

Lightweight breeds are more apt to be excitable, hyperactive, and energetic compared to breeds with heavy bodies.

Coping behaviors in response to stress, such as fly-snapping, are related more to a dog's weight than height. The shorter and stockier the dog, the greater the tendency to display coping behaviors.

Obsessive tail-chasing isn't linked to size or breed, nor is coprophagia (poop eating), chewing, or pulling on leash.

Owners Tend to Tolerate ‘Tiny Terror' Behavior in Small Dogs

In drawing conclusions from their research, the University of Sydney team considered the fact that dog owners may be more tolerant of undesirable behavior in smaller dogs, which may in turn result in increased behaviors such as excessive barking, nipping, eliminating indoors, begging, separation anxiety, and attention-seeking.

The researchers speculate that owners of small dogs may encourage undesirable behaviors and predispose their pets to separation anxiety, puppy-like behaviors, mounting, and begging. The tendency to keep small dogs indoors and under-exercised may also be contributing factors.

"Undesirable behaviors such as owner aggression, or mounting, occur more often among small dogs. This suggests that, in small dogs, these behaviors are tolerated more than they would be in larger dogs where such behaviors are more unwelcome and even dangerous.

Equally, such behaviors in small dogs may be a result of their being overindulged and over-protected," McGreevy explained.

Another consideration is that smaller breeds are known to be more reactive, neurologically, to stimuli in their environment than larger dogs, who tend to be more laid back.

"These findings … remind us that domestic dogs are an extremely useful model for exploring the biological forces that produce diverse animal structures and their related behaviors," says McGreevy.

"The interaction of nature and nurture in producing the relationships we have described in this study creates a raft of fascinating questions that further studies will address."