If your memory is still serving you right you will remember that in biology, we studied temperature – the hotness or coldness of a body. We further studied animals and grouped them into broad two categories namely cold and warm-blooded animals. Warm-blooded animals – Homeotherms are animals most of them mammals that maintain a constant internal body temperature while the opposite was Poikilotherms – whose temperature varies according to the surrounding.
Warm-blooded animals maintain a constant body temperature because of thermoregulation. An in-built physiological mechanism that works through various means to maintain this temperature. These mechanisms include sweating, panting, ear flapping, urinating on oneself, or wallowing in the mad.
What is sweating?
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Strictly speaking only primates like man, apes and monkeys sweat. Perspiration is the release of watery fluid from our bodies in an effort to cool–off. Sweating in primates is animal behaviour that is mostly triggered by high outside temperatures, emotions, stress, certain foods especially those high in caffeine or alcoholic drinks, certain diseases and menopause. Humans have millions of sweat glands concentrated in the armpits, face, palms and soles. Two types of glands help in this namely the eccrine glands that are located all over the body and produce odourless sweat and the apocrine that are located in hairs on our heads, armpit and groin. These ones produce smelly sweat. Horses like primates also sweat to cool down or thermoregulation.
Panting, Flapping and Wallowing in Mud
So how do other animals that do not sweat thermoregulate? Panting is another way of letting excess heat. It is common in canines and felines – dogs and cats. Panting helps to cool the body by exchanging hot (internal/exhaled air) with cold (external/inhaled) air which cools internal organs like the lungs fast and this help to lower the internal body temperature. You have seen dogs doing this all the time after a jog, a fight, or on a hot day.
Animals with large ears will continually flag to regulate their body temperature and the elephant is a good example. Others like hippos will spend a hot day submerged in water.
Sweating like a pig – is a misnomer
You must have heard this old saying – “sweating like a pig”. The pig here has nothing to do with the animal but hot iron and this small space may not allow me to delve deeper. In a real sense, pigs do not sweat. Annoying as it may be, animal welfare activists will insist that you allow your pig to swim in the mud so that it can cool off. The pig does that for two reasons - to cool off and wad off insects (to keep itself clean from biting insects).
On a visit to Bosaso Port in Somalia under an assignment by the African Union InterAfrican Bureau for Animal Resources, my interest was piqued when I spotted hundreds of white cows. After doing some research, I learned some interesting facts. White reflects light and hence causes loss of heat while black absorbs heat. That is why we have black Friesians from cool countries. Now research has it that the black and white stripes on Zebras create micro-breezes that could be working to cool them.
Interestingly, vultures and the stork thermoregulate by urinating or defecating on their scaly feet. This vice is called urohidrosis. Finally, there is a condition called hyperthermia, an increase in body temperature beyond the normal ranges. The underlying cause should be established and a corrective medical measure undertaken quickly. This is a common clinical sign in most diseases.
[Dr Othieno is a veterinary surgeon and currently the head of communications at the Food and Agriculture Organization of the United Nations (FAO) Kenya. The views expressed here are personal]