Cortisol Vacations For Our Pets?


We recently ran across a blog post by a trainer titled “The Cortisol Vacation.”  She was writing about the dangers of chronic stress in dogs and how best to handle it.  She pointed out that when dogs become distressed, an adrenal hormone, cortisol, is released.  To handle chronic stress, she says, we should first give our dogs a break from whatever is distressing them, thus putting them on a “Cortisol Vacation.”  While her advice to protect dogs from distress is reasonable, her terminology and assumptions reveal a common misunderstanding of the relationships among short-term stress, chronic or long-term stress and various physiological measures such as cortisol.

Animals, and people, respond to physical (hunger, cold, injury) and psychological (attempts to escape a predator, a threatening animal) challenges (stressors) through a series of physical and behavioral changes that have evolved to meet those challenges. When faced with these stressors animals may increase their efforts to find food, run from the predator or get angry back at the threatening animal. 

Physiologically the body responds to challenges in a number of ways.  The sympathetic nervous system will, among other things, release the hormones adrenaline and noradrenaline, and either increase or decrease heart rate.  The hypothalamic-pituitary-adrenal system (HPA) will release cortisol or other steroid hormones which have complex effects on a variety of body systems including the brain, and act to increase metabolism and free up glucose for energy.

The immune system also responds to stressors either by increasing or decreasing production of cells for fighting infections. The three systems operate at different rates – the sympathetic system reacts in seconds, the HPA in minutes and the immune system in hours or days.
In responding to brief challenges such as a predator or angry neighbor, the responses of all three systems are also brief.  The sympathetic system may only be activated for a few minutes, the HPA and immune systems for only a few days at most.  When there is a longer term challenge, such as living in a constantly cold environment or in constant fear of another animal, measuring activity of the sympathetic or HPA systems (such as heart rate or cortisol levels in the blood) will show little if any changes, because those systems will adapt or habituate to the presence of the long-term challenge.

So trying to measure cortisol levels in dogs that are enduring chronic stress isn’t helpful.  The dogs have already put themselves on a “cortisol vacation”, even though they are still experiencing distress.  Looking at other physiological measures could be more useful such as how the HPA responds to the injection of other hormones, or looking at signs of immune function.

Using simple physiological measures of stress such as cortisol levels in the blood or behavioral measures such as panting are problematic for other reasons.  First, the mere act of collecting blood or other samples can be a stressor and cause cortisol levels to rise.  Second, the three physiological systems interact and influence the activity of each other making interpretation difficult.  Third, individual differences in genetic predispositions in responding to challenges, prior experiences with different stressors, and other environmental factors such as where the stressor is experienced can all produce dramatically different reactions to the same challenge.   A trained military or police dog will likely respond very differently to a person threatening her with a stick than would a pet dog who has never had such an experience before. 

Finally, many changes in physiological and behavioral measures are non-specific.  That is, dogs don’t just show elevations in cortisol levels when they are facing “bad” challenges, like the guy with the stick, they also show them when they get excited to go on a walk or run an agility course – experiences we assume dogs enjoy.  Researchers typically measure a variety of physiological and behavioral variables and then look at the overall pattern before concluding that an animal is distressed.  

Most of us can’t measure cortisol changes in real time but instead have to rely on behavioral observations to judge whether a dog is distressed.  Rather than speculating or making assumptions about cortisol levels (unless we are conducting a research project) our time is better spent knowing what is normal and not normal behavior for particular dogs, and honing our observational skills so we are aware of subtle behavior changes when they occur.  

If you want to know more about the physiology of stress we recommend:
Terlouw, E.M.C., Schouten, W.G.P. & Ladewig, J. 1997.  Physiology.  In Appleby, M.C. & Hughes, B.O. (Eds.) Animal Welfare. New York, NY: CAB International, pp. 143-158.
Moberg, G.P. 2000.  Biological response to stress: Implications for animal welfare. In Moberg, G.P. & Mench, J.A. (Eds.) The Biology of Animal Stress. Basic Principles and Implications For Animal Welfare.  New York, NY:  CAB International, pp. 1-21.


  • evelyn haskins

    Reply Reply

    I read the original Blog entry and felt that the article was recommending giving our dogs down-time from stressful activities. I thought that the ‘cortisol’ refernce was merely to make a point, — not being scientific.

    On the other hand I have read recently that hair can give a measure of cortisol over time — at least in humans.

    It would be interesting to know whether this would also give a good estimate in dogs.
    A new biomarker for chronic stress: Hair Cortisol

  • I think you make some excellent points – but doesn’t chronic stress still truly exist? And if it exists, how do we approach it, given all these caveats you mention?

    I am working with a reactive dog with a bite history that I believe has lived chronically stressed for the first 6 months of his life. I’ve got him on anti-depressants and I’m working hard to keep him on a predictable schedule, do regular exercise and training, and use all force free methods. However, he MUST learn some survival skills, and be on a DS/CC schedule, or he’ll be PTS. So I can’t reduce the stress of training and desensitization – this worries me, because I’m afraid I’m not addressing the chronic stress properly.

  • Suzanne & Dan

    Reply Reply

    Don’t feel we can really reply or comment Wendy without more specifics. What were the chronic stress” conditions the dog lived under? What behaviors on the dog’s part led to your conclusion that he is still chronically stressed? What sort of “survival skills’ are you referring to? What specifically are the stressors he encounters on a regular basis?

  • April

    Reply Reply

    I was wondering if you could address how chronic stress plays into this? One example of the type of dogs I envision under chronic stress are the dogs that body slam windows and bark hysterically every time anything goes by the house (hyper-vigilant, never resting), then they are walked three times a day where they also lunge, bark, scream and become increasingly aroused. Would a dog undergoing this everyday learn as easily as one who has been inside with windows covered and only walked when triggers can be avoided? Is a dog experiencing such chronic stress releasing cortisol multiple times a day or would you consider avoiding triggers to not be a ‘cortisol vacation’? I had read the article and thought it made sense but now your article is really making me question it. Help!

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