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Scope Series 4 RTÉ Two, Thursday, 7.00pm

Sniffer Dogs

Sniffer DogMan’s best friends are employed in various roles across the globe - search-and-rescue, law enforcement, guarding livestock, sled-pullers and guiding the blind to mention just a few.

There are a variety of reasons why dogs are good at tracking but it mainly comes down to their superior senses of smell, hearing and sight.

Dogs detect sounds as low as the 16 to 20Hz frequency range (compared to 20 to 70 Hz for humans) and above 45 kHz. In addition, they have a degree of ear mobility that helps them to rapidly pinpoint the exact location of a sound.

Eighteen or more muscles can tilt, rotate and raise or lower a dog's ear. 

A dog's ability to detect scents is legendary. Humans are olfactory dunces compared to dogs. The difference is in the anatomy of a dog's nose. Our noses contain two sheets of membranes about the size of a postage stamp, that contain roughly five million olfactory receptors. Dogs, on the other hand, have intricately folded sheets of membranes, with a surface area 50 times larger than that of humans, and with more than 220 million sensory cells.

Sniffer DogSome dog breeds have been selectively bred for excellence in detecting scents, even compared to their canine brethren. What information a dog actually detects when he is scenting is not perfectly understood. It now seems to be well established that dogs can distinguish two different types of scents when trailing - an air scent from some person or thing that has recently passed by as well as a ground scent that remains detectable for a much longer period.

Handlers who train tracking dogs say it is impossible to teach a dog how to track any better than it does naturally. The object instead is to motivate it properly, teach it to maintain focus on a single track and to ignore smells that may otherwise be of greater interest to an untrained dog.

Because of their amazing sense of smell, dogs have even been trained by scientists to detect different types of cancers. British researchers have trained dogs to detect bladder cancer by sniffing human urine. Other research teams, at institutions from Cambridge University in England to Florida State in the US, are testing dogs' ability to detect lung, breast and liver cancer in breath; prostate cancer in urine; and melanoma on skin.

Dogs will not, of course, replace X-rays, CT scans, fibre-optic scopes, mammograms, pap smears and other cancer screens. But some expensive and invasive tests are done only after symptoms are found.

Gas chromatography studies have shown that some tumours exude minute amounts of formaldehyde, alkanes and benzene derivatives not found in healthy tissue. Experiments have shown that dogs can detect chemicals at one ten-thousandth to one hundred-thousandth the concentrations that humans can, while ignoring other odours.


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