Dogs are after you !
Although most humans have a relatively big nose right in the centre of their face, that organ’s main function seem to be there to support the spectacles and to pre-warm the air that enters the nostrils. Our sense of smell isn’t exactly great when it comes to a showdown with other nose-possessing organisms, but when I use the plural “we”, I am not exactly accurate, for female noses consistently outperform those of males and there are even odours that men and children cannot but mature women can smell. There is also the aspect that in women odour thresholds vary over the menstrual cycle. Generally speaking, however, we humans aren’t smell champions and find it hard to understand how a police dog can follow the track of a wrongdoer or a lost person, how salmons sniff out their home rivers on their migrations to their birth stream, how ants smell odour trails laid down by worker ants and how male moths can possibly detect the scent of a female 10 km away.
Humans simply can’t imagine what it means to have a keen sense of smell even though there are some individuals who earn a lot of money with their noses (I am thinking of professional perfumers). The main function of our own noses is to protect our lungs against damage by cold air, to trap particles and bacteria in the mucus of the nasal epithelia and, for those who have to wear glasses, as a convenient support for the specs. It has been calculated that we can detect with our approximately 6 million olfactory receptor cells (= odour receptor cells), 1/500 millionth of 1 mg of mercaptane (a substance with a garlic-like smell and also not unlike smelly feet). However, in terms of molecular threshold (approximately 200 million) it falls far short of the 1,000 required to elicit a response in the moth or the 3,000 in the eel. The dog with a calculated threshold of 3,000 and some 20 million olfactory receptor cells is of course also many log units better than us humans.
Professional tracking dogs perform remarkable feats, but make mistakes when it comes to keeping apart identical twins. But how about a person walking backward? Could that also confuse a tracking dog? Tests in the Swedish Dog Training Centre with two German Shepherd dogs demonstrated that they were not fooled, but consistently followed the direction in which the track maker had walked. Thus, the dogs do not determine the direction as the direction from heel to toe. With interrupted tracks like separate footprints, the dog is apparently capable of discriminating the strength of the odour between successive prints. Continuous tracks like those left by the tyres of a bicycle can be followed easily enough, but to determine the correct direction that the bicycle took appears to be much harder for the dog. Such tracks simply did not seem to contain the appropriate clues. For the dog, simply following a track is therefore quite a different task from detecting the direction of the track. However, my advice to potential burglars is: burglars beware, for in the Swedish Dog Training Centre dog handlers are now training dogs to master even this difficult task!
© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2017.
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