Please act responsibly and consider your pet this summer
I work in research for the most part dealing with human physiology, and often thermoregulation – I am also a loving dog owner. I have participated in research with human subjects investigating cooling strategies for work in the heat including the military, and recently began to wonder how thermoregulation in dogs differs from humans. Many people understand the cooling strategies of the human compared to the dog, mostly, dogs pant and human sweat.
Humans can thermoregulate by using 5 mechanisms, (1) Evaporation, (2) Convection, (3) Conduction, (4) Radiation, and (5) Metabolism. Metabolism is what happens when we exercise and always results in heat gain. Evaporation is how we lose heat from sweat evaporating off of the skin. Convection is the loss of heat by moving air (fans feeling cool on your skin) and Conduction is the loss of heat when we touch a surface that is cooler than our skin temperature (or gain warmth by touching something warm). Radiation often refers to the sun warming our skin.
Dogs gain heat by the same mechanisms that we do, Metabolism from exercise, Conduction from hot surfaces and Radiation from the sun. However their furry coats can help to prevent heat gain from Conduction and Radiation, therefore when you shave your furry dogs coat, you may be doing them a disservice as this may prevent their ability to insulate themselves from the heat.
To lose heat dogs take advantage of Convection, Conduction, and Evaporation. When dogs are outside and there is a breeze or they are moving they can lose heat from Convection, however tied up at home, in a crate, or in a car, they lose the ability to dispel heat this way. Dogs try to use Conduction every opportunity they have, this is why your dog (and mine!) decides to lie down in the mud puddle after a run at the dog park, the mud puddle is slightly cooler than the air and water removes heat from the body 25 times faster than air, so if they are already in the mud puddle, give them a minute to enjoy the cooling effect.
Dogs that are exercising or have just been exercising have an increased heart rate and increased muscle temperature and therefore gain a lot of heat though Metabolism. It is especially not a good idea to leave your dog in the car after a walk in the dog park, he is hotter than ever as he still has a lot of heat stored in his body from the exercise.
I think we all understand a major source of heat loss for dogs is Evaporation, and since they don’t sweat they can’t evaporate from their skin so they rely on their nose and mouth. It is important if you use a halter or muzzle on your dog that it NEVER impedes their ability to pant. During conditions of high environmental humidity, panting is less effective in dissipating heat. The humidity only needs to be 35% to instigate significant differences in heart rate, venous pH, and core temperature of dogs. The relative humidity in Ottawa today (July 21) is 57%, at 26°C.
It is also important to understand that your pooch needs to acclimatise to the hot temperatures of early summer, a run in the middle of the day in the first few weeks of summer may be more tolerable at the end of summer when the dog has acclimatised.
Controllable conditions that you are responsible for, which result in heat gain include; lack of acclimatization, water deprivation, high humidity, and confinement to compartments with poor ventilation.
Lastly dogs with excess fat, which causes increased insulation in obese animals, impairs normal heat dissipation. In addition, older dogs may have similar problems functioning in hot environments.
There are various products on the market to increase cooling for your dog, beds, bandanas, and vests, but the most affordable is probably a kiddie pool for your backyard. Nothing cools better than cool (not cold!) water exposure. We live on the water and our Golden Retriever makes frequent trips to submerse herself in the water every day through-out play time.
If you do suspect that your dog or a dog you discover has heat stroke or heat exhaustion here are some signs, although these vary depending on the source of information.
Heavy panting, hyperventilation (deep breathing), increased salivation early then dry gums as the heat prostration progresses, weakness, confusion or inattention, vomiting or diarrhoea and sometimes bleeding. Shallowing of the breathing efforts and eventually slowed or absent breathing efforts, vomiting and diarrhoea that may be bloody and finally seizures or coma.
You may have to get help to move the dog, since collapse is possible with severe overheating. DO NOT expose the dog to very cold water or ice. You use cool water or tap water. Ice cold water causes the blood vessels in the skin to constrict or get smaller and will decrease the amount of heat you can remove. This same cooling strategy applies to humans with heat stroke/exhaustion.
If possible take their rectal temperature. Begin to cool the dog by wetting with cool water poured over the body. Many Vets suggest using soaked cool towels and applying them especially to the groin and auxiliary areas. Spray water in their mouths, apply alcohol or water to their pads of their feet, as the evaporation of alcohol cools even faster. Direct a fan at the dog to help with the evaporation process.
Sadly even those who should know better have allowed their dogs to die in the heat. Recently the Police in England left 2 trained German Shepherd police dogs inside a car, while the outside temperature was only in the 20°Cs the car heated up much more than the outside and the dogs died. In the same few weeks 4 dogs died in cars in Scotland at only 26°C. Evidence suggests that if it is 29°C outside, after ten minutes, even with the windows slightly open it will be 40°C in the car, and after 30 minutes up to 50°C. After 15 minutes of these temperatures dogs can begin suffering from brain damage.
There are many cases of people acting on the good Samaritan Act and calling the authorities upon discovering dogs in hot cars, people are often fined after the authorities break in a save the animal.
Article written by Dr. T Reilly
- W. Shannon Flournoy, et al. 2003 Heatstroke in Dogs: Pathophysiology and Predisposing Factors*Vol. 25, No. 6 June
- T. Greenlee. Temperature Adaptation in Northern Dogs