Stress can be defined as “any factor that threatens the health of an organism or has an adverse effect on its functioning. Such factors or stressors may occur in the external environment or arise within the body” (Concise Veterinary Dictionary, 1988).
While the words stress and distress are often used interchangeably, there is a difference.
Stress is a normal feature of life for all animals and serves important adaptive functions, such as flight-or-fight, predation, or “social-climbing”. “Distress “occurs when an animal is unable to adapt completely to a stressor.” (Rollins and Kessel. , 2017).
The transition to distress occurs when the body cannot cope against the assault of one or more stressors. “Stressors” are events that precipitate stress (Committee on Recognition and Alleviation of Distress in Laboratory Animals, 2008)
When a dog is stressed, he or she experiences physiological changes over which he or she has no control. These include increased blood pressure, heightened senses, increased ability of the blood to clot, and increased heart rate. These changes all help the dog to respond to potential danger.
Physiological indicators of stress can be identified through the measuring of the of heart rate, blood pressure, respiratory rate, body temperature and through evaluations of immune status and disease incidence. Measuring hormone secretion is also used in assessing stress (Bodnariu 2008).
The urinary, gastrointestinal, reproductive, and immune systems have been shown to be susceptible to developing disease because of stress (Mills, Karagiannis and Zulch 2014).
Some dogs are stressed by spending long hours alone. Studies have shown that at 5 weeks of age, dogs experience an elevation in cortisol after separation (Nagasawa, et al. 2014). Dogs who have separation-related problems may show it through destruction of property, excessive vocalization and house-soiling.
A study on treatment for separation-related behavior revealed that dogs treated with systematic desensitization had significant reductions in the frequency and intensity of the separation-related behaviors and that, three months after the treatment ended, most of the dogs showed almost complete elimination of the problem behaviour (Butler, Sargisson and Elliffe 2011).
Stressors can include threatening or aggressive behavior (perceived or real) from other dogs or from people, punishment, wearing punishing equipment, too much or too little activity day after day, being hugged or stared at and being bothered while he or she is sleeping.
Certain training methods can also elicit stress signals in dogs. The results of a study comparing the behavior observed in dogs participating in training classes at two training schools that used two different types of training methods results suggested that training methods based on positive reinforcement are less stressful for dogs. One school used positive reinforcement (where a food reward was given) in training while the other school used negative reinforcement (where an aversive disappeared when the dog complied). The dogs who attended the classes at the school using negative reinforcement displayed lowered body postures and displayed other signals of stress while the dogs who were trained with the positive reinforcement showed increased attentiveness toward their owners (Deldalle and Gaunet 2014).
Owners can identify stress signals in their own dogs. By looking at the whole dog and all the indicators one can interpret the dog’s behavior. When stressed, often the eyes will look rounder than usual and are opened widely, the whites may show. Generally, the dog will be looking away from the trigger or stressor, ears will be flat against the head, he may be panting or his lips are pulled up to reveal the front teeth or pulled well back to reveal front and back teeth. The tail may be tucked between his legs. His hair may stand on end and he may
shed more than usual. Often stressed and fearful dogs will lean away, crouch, roll over, freeze and may urinate or defecate (ASPCApro
They may vocalize also. Howling, whimpering, high-pitched repetitive barks and growling can all indicate stress and distress.
Some dogs urine mark when feeling stressed.
Research has revealed three categories of abnormal behaviours in dogs that can be caused by stress:
(1) displacement activities such as licking, grooming and pica (“pica” refers to the eating of substances that have no nutritional value)
(2) stereotypical activities like excessive licking, flank sucking, circling or whirling, tail chasing, fence-line running, excessive barking, polydipsia (an abnormal increase in thirst) and polyphagia (an abnormal increase in appetite)
(3) behaviours like staring and ‘fly chasing’ referred to as “hallucinatory” behaviors (Casey, et al. 2002).
A stressed dog may have changes in appearance. A recent study indicated that premature greying in dogs under four years of age may be an indicator of anxiety, fear or impulsivity (“impulsivity” was defined as the loss of focus, an inability to calm his or herself, jumping on people, and hyperactivity after exercise). Analysis showed that muzzle greyness was significantly predicted by fears of loud noises, of unfamiliar animals, and of unfamiliar people. (King, et al. 2016).
For dogs who are experiencing chronic stress from kennelling, research has shown that even one night away from the kennel situation results in a reduction in cortisol in dogs. Cortisol is a diurnal hormone that is a measure of stress. In a study done at Best Friends Animal Sanctuary in Utah, researchers measured cortisol levels in the dogs who lived there and who were participating in the “sleepover program” where visitors can take a dog for the night to their hotel. They found the cortisol levels in the dog dropped significantly when the dog participated in the sleepover program (Seckel 2017).
In another study, half of the dogs adopted from shelters displayed symptoms of various illnesses such as diarrhoea, vomiting, coughing, sneezing and skin problems. It was suggested that these conditions may be due to the immunosuppression caused by the previous stress of kennelling (Bodnariu 2008).
Recognizing the indicators of stress in dogs helps us make changes to reduce stress and avoid distress in dogs.