Temperature Adaptation in Northern Dogs
by Ted Greenlee
January, 1971 Newsletter of the Samoyed Club of Colorado
March, 1971 issue of "Northern Dog News"
we left the Pacific Northwest and moved to Florida with our Samoyeds, I
been asked how they tolerated the heat in this climate. The question usually
produced my "five minute lecture" on Northern Dogs in the South.
When I repeated this jist of this lecture to Doris and Harold McLaughlin
they requested that I write a short paper discussing how Northern dogs adapt
to varying temperatures. This discussion actually revolves around at least
scientific works on the ability of arctic animals - seals, whales and Northern
dogs among others - to stand exceedingly low temperatures, and on the methods
of heat exchange in dogs.
specifically asked to write this discussion in lay terms "as I spoke them".
Since most of my writing activities are related to writing for scientific
I find this a very difficult task, but I shall make an attempt. In general,
in attempting to discuss work of a scientific nature in lay terms one either
talks over the heads of some readers or beneath the knowledge of others and
never quite finds the individual who has exactly the right amount of information
as you write the article. To begin with, I would like to review a little
information in relation to temperature control that I am sure most people have
been exposed to at some time. The main consideration is that the dog, similar
to man, will not tolerate significant variation of his body temperature.
most of the reactions taking place in the body, energy producing reactions
much like the reactions in an automobile engine, produce heat. Intemperate
where the outside temperature is fairly close to body temperature, the primary
concern for the animal is to get rid of the excess heat produced. In the
of the automobile, one circulates water through the engine and then passes
it through a radiator that has a relatively high degree of efficiency at
the heat from the water to, in this case, the air. In general, this is not
a terribly efficient method, though it is adequate in the case of the automobile.
case of man, the radiator, for all practical purposes, is his exposed skin.
In order to enhance the loss of heat, man uses the simple principle of evaporation.
In general, the amount of heat loss by the evaporation of a certain volume
water from the skin is some five-hundred and forty times greater than the raising
of the same amount of water one degree in temperature. This principle of
is very important in many cooling systems and particularly in the cooling of
the body. If, however, the major problem ceases to be that of getting rid
excess heat, but rather maintaining what heat is produced in the chemical reactions
in the body, one has to look to different techniques. In general, this only
becomes necessary if an animal is forced to live in a climate where the temperature
is much, much lower than body temperature. This, of course, is the case of
Northern dog. The best way to conserve heat is the well-known method of insulation.
The arctic dog's coat is so constructed that it is a very efficient insulator.
Therefore, little of the heat produced by the body is lost by means of contact
with the outside air through the skin. This, of course, is very good in the
winter; but unfortunately, Arctic areas in summer can reach very high temperatures,
somewhere in the 70's and 80's or even higher for short periods of time.
therefore, the animal must also be able to adapt to this increase in temperature.
It so happens that the insulation principle is still of use to the animal.
one lives in warmer climates, it is much easier to air-condition a well insulated
home than it is to air-condition one that is not insulated. In the case of
animal, the only requirement is that there be some relatively efficient mechanism
that the animal can turn on to dissipate his own heat. With a well-insulated
body, he will be very little effected by the outside temperature once this
is established. The animal then can maintain his body temperature with changes
in outside temperature. Animals that have not adapted this type of mechanism,
that is an insulated mechanism, not only will be susceptible to cold, but
also be very susceptible to an abnormal increase in the outside temperature
as compared with what he is used to. Therefore, the Northern dog in southern
climates will do as well or better in excessive heat that the short-haired
who is very susceptible to heat stroke.
I would now like to discuss two mechanisms of heat control, one which is utilized specifically in the case of Northern animals, and one which is utilized by dogs in general. I would first like to discuss the problems of severe cold and how the animal protects his body temperature in addition to his insulation. It is not possible to totally insulate the dog and in general, the areas not adequately insulated are the areas that are in contact with his snowy world. Those areas are, of course, his feet and legs. Problems of the feet and legs, or in the case of man, the hands and feet, are frequently noted in cold exposure. Man, who is not well insulated, to protect his body temperature and vital organs, will literally shut off blood supply to the feet and hands. When one goes out in the cold and is not properly dressed, one's feet and hands become extremely cold and frostbite or freezing of the fingers and toes is a common occurrence. If this process was followed in the case of a dog in his 60 to 70 degree below zero weather, he would of course be in very bad straits. Therefore, instead of stopping the blood supply to the extremities so the blood does not become chilled, what occurs is that the warm, oxygen carrying arterial blood going into the limb runs right next to the cold, unoxygenated blood leaving the limb. Since they are right next to each other, the warm blood gives up its heat to the cold blood, preventing the loss of this heat as it gets down to the exposed part of the dog's foot. The oxygenated blood can get to the vital parts of the foot to maintain their nutrition, but at the same time does not allow a loss of body heat to the cold air.
The ability of the animal's foot and lower leg to live at very low temperatures requires addition adaptation of the tissue, some of which is not well understood. There is one example though that is well understood and noted, and that is the difference in the melting (or freezing, Ed.) temperature of the fat associated with the foot and legs compared to the melting temperature of body fat. The best example of this noted in the case of neatsfoot oil which is the fat from the foot of a cow as compared to the tallow which is the fat from the body of the cow. As you remember, neatsfoot oil is a liquid at normal room temperature, whereas tallow is solid. Therefore, the fat is adapted in the foot of the animal to keep it from becoming solid at these low temperatures and becoming brittle and breaking. I am sure there are other changes in the cells in the tissues of these parts which allow them to tolerate this lower temperature and still function for the animal, but the heat exchange mechanism between the arterial and venous blood in the limbs of cold adapted animals is absolutely essential to their survival.
It is possible
that a reverse heat exchange takes place in hotter weather. In this instance,
blood going to the feet would pick up excess heat in the blood leaving the feet
and carry it away from the body, thus preventing a dangerous increase in the
animal's body temperature. I doubt, however, if this reverse mechanism plays
as important a part in the loss of body heat during hot weather as the heat
exchange mechanism does in the protection of the animal in the cold.
the total animal is covered with an insulated coating, perspiring for the
of heat through the large area of the skin of the body as in man is not practical.
Therefore, the animal must have another means of heat loss. Anyone who has
with dogs knows that the dog pants when he is hot. It is his panting mechanism
that allows the dog to lose heat he does not need when the weather is hot.
mechanism functions on the principle of evaporation. As I have said before,
evaporation is extremely effective because you can lose almost five-hundred
and forty times as much heat without changing the temperature of the air
all. This evaporation takes place in the dog's nose and is enhanced by the
fact that there are many folds of tissue in the nose which increase the surface
that the air is in contact with. In addition, this tissue actually perspires
and has a large blood supply, thereby acting much like the radiator in the
This makes a good mechanism of heat loss, but one needs some way in which to
shut it off when one does not want to lose heat. Since the animal must breathe
and must take in a pretty constant volume of air at all times, because varying
this volume of air would interfere with other bodily functions, people have
often been concerned as to how this is controlled. A recent study, just published,
has looked into this problem and has come to this conclusion. The air is
in through the dog's nose and in the case of panting is exhaled through the
mouth. In doing this, the air picks up much moisture and heat from the nose,
this cooling the nose and drying it. When it is exhaled, it is exhaled through
the mouth and since there is much less blood supply to the area around the
and the surface area is much less, almost all of the moisture is absorbed and
the heat will leave the dog's mouth and be lost. When the dog does not wish
to lose body heat, he simply exhales the air that he has brought in through
the nose back out the nose, in which case a great proportion of the moisture
and heat will be returned to the large surface area and the membranes in
nose thus minimizing the loss of heat. Therefore, when an animal is hot, the
hotter the animal is the more of the air he brings in through his nose will
be exhaled through the mouth, thus the wide open, tongue out position. If
does not wish to lose heat when it is cold out, he will breathe in and out
through his nose and keep his mouth closed. The tongue provides a quite sensitive
of temperature control, particularly in the case of the animal who has other
means of protecting himself from the cold and from the outside temperature
do the long-haired Northern breeds. The animal, therefore, in general has developed
enough capacity of heat loss through his panting mechanism to compensate
the very wide swings in temperature.
case of man, the removal of clothing during hot weather increases the ability
to lose heat by evaporation of moisture. The dog does not have this ability
and therefore his insulation is a protection to him during hot weather. If the
animal loses his insulation during very hot weather, by having his coat clipped
for instance, he runs the risk of not being able to maintain his body temperature.
His skin temperature loss probably is not only inefficient but, since he does
not perspire, he will probably increase the temperature of his skin and his
body temperature as well.
that would interfere with a dog's ability to pant efficiently can also be a
great danger to him in hot weather. It is not uncommon to hear of animals who
have died of heat stroke after having been given an anesthetic for some minor
surgical procedure and then left in a hot car. If the animal is not wide awake
or has had an anesthetic, he is not able to compensate for the increased temperature
by increased panting. The animal locked in a hot car does not have the ability
to open the window as do people and is, of course, very susceptible to heat
stroke and death. The dogs in our experience that are most susceptible to hot
weather and to sickness from heat are those that have a poor panting mechanism,
i.e., the short-nosed dogs such as bulldogs, Pugs, etc. They are extremely susceptible
to high temperature and tolerate Southern climates such as ours very poorly
unless they are kept in an air-conditioned house.
the important point to remember in relation to Arctic breed, is that these breeds
were able to survive in the Arctic not only because they could tolerate cold
but because more precisely, they could tolerate extremely wide swings of temperature
in relation to their body temperature. Therefore, they are also, it appears,
better adapted for severely high temperatures. The animal that was selected
by living in a temperate climate, that is, one in which the temperature stayed
very close to the animal's body temperature throughout the year, is not only
going to be very susceptible to cold weather, but also is going to be more susceptible
to severely hot weather which is well over the dog's body temperature.
The final point I'd like to make to in my "Five Minute Lecture" on Northern Dogs in the South is that the Arctic breeds are probably the best heat adaptable dogs one could find, so therefore, I would not be fearful of their presence in a hot climate. However, I might add, there are other problems associated with hot climates such as increase parasites and skin problems that do cause the long-haired Northern dogs to have greater problems than do some of the short-haired breeds.