A study performed by researchers at the School of Animal and Veterinary Sciences at the Roseworthy Campus of the University of Adelaide looked at the behaviors of 26,555 dogs and their experiences with veterinary visits. 

The dog owners indicated the level of fearfulness shown by their dog during a veterinary examination including signs like avoiding eye contact, avoidance of the feared object; crouching or cringing with tail lowered or tucked between the legs; whimpering or whining, freezing and shaking or trembling.   Extreme fears were also noted and were described as: “exaggerated cowering, and/or vigorous attempts to escape, retreat or hide from the feared object, person or situation.” 

According to the study, 41% of the dogs exhibited mild to moderate fearful behavior, and a total of 14% of  dog owners reported that their dog showed severe or extreme fear during the veterinary examination.  

The single most important factor in determining whether a dog would be fearful appears was breed. The study found that the most fearful dogs were the toy breeds, mixed breeds, and hounds. The lowest degree of fearfulness was found in working breeds like  boxers or Doberman pinschers, Siberian huskies, and Bernese Mountain dogs. Extremely low levels of fearfulness when medically examined also appeared in hunting dog breeds, including spaniels and retrievers.  

A dog's size also predicted their fearful behavior when encountering a veterinarian. Larger dogs (those over 22 kg, or 48 pounds) were considerably less afraid of the veterinarian than were smaller dogs.

The dog's social environment was also important. Dogs that were living alone in a home were found to be more fearful than dogs living in a household that contained other dogs.

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Which dogs are more afraid of veterinary clinics