A dog's nose knows
May 17th 2009 04:46
What have a dog's nose and a community newspaper in common? The answer is a great deal, for they both deliver a lot of local news.
A dog's sense of smell is its most powerful sense, and it depends on smell to interpret the world around it as much as humans depend on sight.
Dogs have about 25 times more smell receptors than humans. When a dog takes a normal breath, air doesn't pass directly over the smell receptors. But when it takes a deep sniff, air reaches the receptors near the back of the snout, and provides an enormous amount of detailed information.
An experiment was once conducted in which 12 men walked a small distance one after the other, each carefully stepping exactly in the footsteps of the first man. At the end of the stipulated distance, each man walked off in a different direction and hid. After all were hidden, a dog which belonged to the man who had walked first was brought to the starting point. The dog had no trouble finding the hiding place of his master by following his scent.
Dogs can sense smells at concentrations about 100 million times lower than humans. They can, for example, detect one drop of blood in five litres of water.
Humans have found many ways to utilise this sophisticated sense of smell. Police and military tracker dogs and sniffer dogs at airports are well known, but scientists are finding new ways to use dogs in detecting disease. Dogs have already been trained to warn of epileptic seizures, low blood sugar and heart attacks, although interestingly it is not known whether dogs detect such changes using smell or sensing something else.
Much of the research in this area is based on the theory that disease causes subtle chemical changes in the body or alterations in metabolism, which in turn releases a different smell, or chemical marker.
Almost all dog noses are black, but it is not known why. Only two breeds do not have black noses, the weimaraner and the viszla. Puppies can have non-black noses too, but by the time the dog has matured its nose will be a uniform black. The reason could be to protect against sunburn.
The moisture of a dog's nose is caused by the mucus lining The evaporation of moisture from the nose helps to cool the dog, but the moisture also makes the nose more sensitive to odours. A happy dog continually licks his nose while an unwell dog tends not to lick his nose, giving rise to the common perception that a dry nose is a signal that a dog is ill.
This is not always the case however, as breeds such as bulldogs, Boston terriers and pugs, known as the brachycephalic breeds, can't reach their noses with their tongues, and their noses are consequently prone to dryness and cracking.
Boston terriers can't lick their noses
Weimaraners have colour-coordinated coats and noses
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