Sweating in animals
Do animals also sweat like humans?
T.S. Keerthika, Chennai
ANSWER 1: Sweating or perspiration is a means of reducing body heat among warm-blooded terrestrial (land) animals.
Some wastes are also removed as salts. As the temperature variation in water is slow and marginal, aquatic animals do not have this problem. In cold-blooded land animals, body temperature varies according to the atmospheric temperature.
On the other hand, warm-blooded animals have to keep their body temperature constant. For this they resort to conduction, convection, radiation and evaporation of water when hot weather or exercise heats the body. Body heat is absorbed by the water present in body fluids and carried to the outer surface to be vaporised.
There are two types of perspiration — insensible and sensible. In insensible perspiration water from the body fluids diffuses through the skin and vaporises without wetting the body.
Sweat glands have no role in this. Water lost during respiration, as we exhale comes under this category. This is inadequate during muscular exercise or at a higher atmospheric temperature. Now the sweat glands start working.
They provide water for evaporation. This is sensible perspiration. On very hot days a man may lose about 1 litre of sweat per hour, thereby reducing 600 kcal of heat. In other warm-blooded animals sweat glands are totally absent or present in lesser numbers. Birds and some mammals lack sweat glands.
In cats, rats and mice they are confined to the soles of the feet. In rabbits, they are around the lips; in bats on the sides of the head; in cattle on the muzzle; in hippo on the pinnae. Hippos and giant kangaroos have red sweat. Birds resort to panting, losing water from air sacs. Dogs also adopt panting. Their tongue has rich blood supply from where water is evaporated.
FRANCIS EDATHRAKARY
Department of Zoology
Bharata Mata College
Thrikkakara, Kochi
ANSWER 2: In animals, three major mechanisms are observed for their body temperature maintenance, sweating being the first and foremost.
Several furred animals, in particular those of large body size such as cattle, large antelopes and camels depend on sweating for evaporative body cooling.
Though sweat glands are present in all mammals, few especially those belonging to the dog family, small ungulates such as sheep, goat and small gazelles cool primarily by a second method of panting because of the fewer number of sweat glands. Third method of salivation and licking is common in Australian marsupials including large kangaroos and some rodents.
Sweat glands in animals are of two types: eccrine glands which are supplied by cholinergic fibres present in sympathetic nerves, and apocrine glands which develop from hair follicles. Unlike humans, in domestic animals apocrine glands are important for evaporative loss. In contrast to mammals, birds have no sweat glands and they maintain their body temperature by rapid oscillation of the thin floor of the mouth and upper part of the throat.
DEEPU MATHEW
Field Research Laboratory, Defence Research
and Development Organisation, Leh, Ladakh
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