|
HOME
About US Available
Retired AKK Our Males
Our Females
The Legend
Breed History
Breed Standards
Breeding for
Color
Red AKK
Documents
Contact Us
Questionnaire
Whelping Calendar
| |
Temperature Adaptation in Northern Dogs
By Ted Greenlee
January, 1971 Newsletter of the Samoyed Club of Colorado
March, 1971 issue of "Northern Dog News"
Since we left the Pacific Northwest and moved to Florida with our Samoyeds, I
have frequently 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
recently, they requested that I write a short paper discussing how Northern dogs
adapt to varying temperatures. This discussion actually revolves around at least
two 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.
I was 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
literature, 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 basic 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. Also, most of the reactions taking place in the body, energy
producing reactions much like the reactions in an automobile engine, produce
heat. Intemperate climates, 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 case 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 transferring 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.
In the 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 of 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 evaporation 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 of 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 the 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. So,
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. If 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 the 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 mechanism 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 will 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 dog 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.
Now, since the total animal is covered with an insulated coating, perspiring for
the loss 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 dealt 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. The 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 at 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 area 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 car. 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 brought 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 mouth 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 the 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 he
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 provides a quite sensitive means
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 as do
the long-haired Northern breeds. The animal, therefore, in general has developed
enough capacity of heat loss through his panting mechanism to compensate for the
very wide swings in temperature.
In the 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.
Anything 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.
I think 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.
| |
We do transport puppies but not by postal service.
place holder
|
