How your dog’s size and shape influences her behavior

By Dr. Karen Becker


A study published in 2013 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.1 Using the Canine Behavioral Assessment and Research Questionnaire (C-BARQ) as a data-gathering tool, the research team analyzed information on 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.

“[In] the most comprehensive study undertaken to date, our research shows that certain physical characteristics in dogs are consistently associated with certain types of behavior,” lead study author Paul McGreevy, Ph.D., 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.”2

33 of 36 unwanted 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 body weight decreased, excitability and hyperactivity increased. The study revealed that 33 out of 36 undesirable behaviors were associated with a dog’s height, body weight and the shape of her skull. Some of these included:

Begging for food Urine marking
Fear of other dogs Peeing or pooping when left alone
Non-social fear Separation anxiety
Attention-seeking Sensitivity to being touched
Mounting people or objects Aggression toward owner

Additional revelations about dog size and behavioral tendencies

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. Some 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 and even encourage bad 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.”

Tiny terror training tips

If you’re a small dog parent and the above study findings resonate with you, there’s no time like the present to help your little one become a better canine citizen. Training a small dog is really no more difficult than training a large one — you just need to make a few accommodations for size.

  1. Stand small — Towering over a dog is intimidating when the animal hasn’t yet learned human body language and vocal tones. And the smaller the dog, the more overwhelmed she can feel in the presence of a big hulking human.

So, when training your little one, until she’s had some experience reading your signals, be sure to show her welcoming eyes, small movements and a soft voice. Don’t deal with her “head on” immediately. Turn slightly to the side and get down close to her level instead of looming over her.

  1. Use small training treats — Tiny dogs need only tiny training treats. Otherwise, you’ll own a not-so-tiny dog in no time. Anything more than, say, a treat the size of a housefly, is too big. You can buy or make treats to break into very small pieces; you can also use some of his regular food, subtracted from his meals, as treats.
  2. Train on her level — Training a small dog from a standing position can be merciless on your back, and the last thing you want is to be in pain when you’re trying to focus on molding your pet’s behavior. Initially you should sit on the floor not only to save your back, but also to appear less intimidating.

Other ways to do training exercises include sitting on a low stool or chair or moving your dog to a comfortable raised surface such as a table or bed.

  1. Use tiny toys and training tools — Your small dog needs a lightweight collar, harness and leash. Generally speaking, leather and chain collars and leashes aren’t a good idea for little guys. I always recommend harnesses for small dogs to avoid neck injuries. Some very small dogs have incredibly fragile necks. And just as his treats should be an appropriate size, so should your small dog’s toys and other supplies like food and water bowls, crate, etc.
  2. Teach your dog a verbal “lift-off” cue — Small dogs are often startled to be suddenly lifted off the ground by a human. If you put yourself in her place, imagining at any moment you will lose the ground beneath your feet, you can see why this is a stressful event. That’s why it’s good to train your dog with a verbal cue that signals you’re about to pick her up. Just make it a simple one-word signal.

To train her to the cue, put your hands on her, say the word and apply just a bit of pressure without actually lifting her. This gives her time to understand she’s about to be lifted. When you know she’s aware you’re about to pick her up, go ahead and do so. Consistent use of the cue will help her learn to prepare for “lift off.”

  1. Respect his smallness — Little dogs can be difficult to train to lie down – and there’s a good reason for it. Your pet is already small and vulnerable, and he knows it. When he’s lying on the floor, he’s even smaller and more vulnerable. He’s also likely to be more sensitivethan a bigger dog to cold, hard or rough surfaces. So, train your little guy to lie down using a soft, raised surface. He’ll feel less threatened and comfier.
  2. Give your little dog some space — As much as possible, your dog should be allowed to meet new people and dogs on her own terms. Picking up a shy or frightened small dog to force an introduction removes her ability to keep her distance if she needs to. So, leave her on the ground, and respect her wishes. If she seems skittish or unfriendly, don’t force the issue. This may be an area where extra work is needed to properly socialize your pet.
  3. Set big dog standards for your small dog’s behavior — If you wouldn’t allow a 70-pound dog to jump up on you, don’t accept the behavior from your little one. Reward only desirable behavior and ignore behavior you want to extinguish. Little dogs can learn to sit and stay just like the big guys do. The same goes for jumping up into your lap, charging out the door ahead of you or ripping treats from your fingers. Don’t accept rude behavior just because your pet is small.

Lastly, treat your little dog like a dog! He’s not a baby or a dress-up doll. He needs to be socialized, which means having lots of positive experiences with other dogs and people. He needs to be on the ground much of the time so he can learn how to climb stairs, get into and out of your vehicle, and move confidently on all kinds of terrain.



Canine Aggression

By Dr. Karen Shaw Becker and comments by Diane Weinmann

Aggression in dogs can be a touchy subject, because there are many competing schools of thought on what causes it, as well as a lot of emotion around the issue. However, no matter the cause, we can all agree aggressive behavior in canines is a significant problem, with serious ramifications.

Millions of dog bites occur in the U.S. each year, and thousands of people seek medical treatment for their injuries. In addition, aggressiveness is the leading reason for relinquishment of dogs to shelters. Given the extent and seriousness of the issue, it’s important to investigate all potential causes and remedies for canine aggression.

Toward that end, a group of university biologists has been studying the role of two specific hormones in domestic dog aggression, and published their findings recently in the journal Frontiers in Psychology.1

“If there are ways to intervene and affect biological processes that produce aggression, that could have a huge benefit both for people and dogs,” says Evan MacLean, Ph.D., assistant professor of anthropology and director of the Arizona Canine Cognition Center in the University of Arizona School of Anthropology.2

Two Hormones That May Play a Role in Dog Aggression

Past studies of aggression in dogs and other animals have explored the role of testosterone and serotonin. MacLean and his collaborators decided instead to evaluate oxytocin and vasopressin because they’re often considered the “yin and yang” hormones and may play an important role in shaping social behavior.

Oxytocin, nicknamed the “love hormone,” increases in humans when they are physically affectionate with a loved one. Vasopressin, while closely related to oxytocin, is associated with aggression in humans. In fact, studies show high levels of vasopressin in people with chronic aggression problems.

Study of Dogs Shows Link Between Increased Vasopressin Levels and Aggression

For their study, the researchers recruited leash-aggressive family dogs of both sexes and varying ages and breeds. They paired each of those dogs with a nonaggressive dog of the same sex, age and breed (the control group).

Each dog in the study was held on a leash by its owner while a person across the room and behind a curtain played a recording of a dog barking. Then the curtain was pulled back, revealing a life-size dog model with a human. The same scenario was repeated with everyday noises coupled with three common objects: a cardboard box, a trash bag and a yoga ball.

The dogs’ responses and hormone levels were assessed both before and after each presentation. None of the dogs showed aggression toward the box, bag or ball. However, many of the leash-aggressive dogs had aggressive responses (growling, barking and lunging) to the life-size dog model, and those same dogs had higher levels of vasopressin in their systems.

The oxytocin levels remained about the same in the two groups of dogs, so the researchers compared their levels to the oxytocin levels in a group of assistance dogs who are selectively bred to have nonaggressive temperaments. The assistance dogs had higher levels of oxytocin than the study dogs, and higher oxytocin-to-vasopressin ratios as well.

“Seeing high oxytocin levels in assistance dogs is completely consistent with their behavioral phenotype — that they’re very, very friendly dogs that are not aggressive toward people or other dogs,” MacLean said.

These study results suggest a link between vasopressin and aggression, and they also suggest that oxytocin plays a role in inhibiting aggression in dogs.

Findings Could Open the Door for New Ways to Manage Canine Aggression

Past research has focused on the role of testosterone and serotonin in canine aggression, with the result that dog parents are often advised to neuter male dogs to lower their testosterone levels either to prevent or treat aggression. Serotonin is thought to reduce aggression, so it’s not uncommon for dogs with aggressive tendencies to be treated with SSRIs (selective serotonin reuptake inhibitors), which are antidepressants. Neither of these solutions is ideal for every aggressive dog.

Research into vasopressin and oxytocin may lead to new approaches to treating aggressive dogs. Unfortunately, with conventional veterinary medicine leading the charge, those new approaches will most likely be in the form of synthetic drugs that manipulate natural vasopressin and/or oxytocin levels in the body. The good news is the holistic veterinary community is often able to use this type of research to discover nontoxic substances with similar actions and few or no side effects.

Life Experiences May Play a Role in Increasing Vasopressin Levels

MacLean believes life experiences may play a role in increasing a dog’s level of vasopressin.

“There’s a lot of work showing that experiences in your lifetime can change the way hormones function,” MacLean told ScienceDaily. “For a lot of dogs that have aggression problems, the owners report that the onset of the aggressive symptoms happened after some sort of traumatic experience.

Often it was that the dog was attacked by some other dog and is in a hypervigilant state after that event — almost like a post-traumatic reaction.”

The good news is that it’s possible to influence your dog’s behavior by interacting with him in a friendly, nonthreatening way. Studies show these types of loving dog-human interactions actually increase oxytocin release in dogs, and lower vasopressin levels. An added bonus is that your hormone levels also respond positively:

“These are bidirectional effects,” says MacLean. “It’s not just that when we’re petting a dog, the dog is having this hormonal response — we’re having it, too.”

The Ultimate Goal: To Preserve and Protect the Unique and Long-Standing Relationship Between People and Their Dogs

In the final paragraphs of the study, the co-authors make a compelling case for why their work is so important:

“Ultimately, dog aggression is a normal and adaptive social behavior, but expressed in the wrong contexts, or to an extreme extent, its consequences jeopardize the welfare of both humans and dogs in our society. It is likely that dog aggression can be motivated by diverse psychological states, including fear and anger.

These emotional processes may be facilitated by, or produce effects on, OT [oxytocin] and AVP [vasopressin] signaling in the brain. Thus, it is important to consider dog aggression at multiple levels of analysis, addressing both the cognitive processes (e.g., appraisal, learning, inhibition), and underlying physiological mechanisms, which mediate these behaviors.

The studies presented here suggest that OT and AVP may play important roles in these socioemotional processes, and set the stage for future work evaluating whether treatments and interventions for aggression can be improved by considering the roles of these neuropeptides.

Ultimately, we hope that these investigations will lead to increased knowledge of the biology of social behavior, promote human and animal welfare, and help to preserve the unique and long-standing relationship between humans and dogs.”3

Dogs with aggressive or fear-based behaviors aren’t happy campers, and studies such as this one shed light on how we can make life better for those pets and their humans. Dogs are individuals, and a dog’s seemingly inappropriate response to certain stimuli may be entirely appropriate based on his internal wiring and life experiences.

How we manage dogs with aggression is critical in helping them have happier futures, and new treatments coming out of studies like this may provide promising adjunctive therapies to behavior modification programs that help aggressive dogs live more balanced lives.

Diane Weinmann’s dog, Neko, started becoming dog-aggressive while in his backyard and on walks in the parks when he reached the age of 6.  He was raised with a lot of dogs to play with so I feel that it’s definitely hormone based issue.  He’s never had a traumatic incident with another animal that would cause his behavior.  I wish the holistic vets would come up with an essential oil or herb blend to help this issue.