- How do dogs find people buried in an avalanche?
- Do all dogs have the same sense of smell, or do dogs with bigger noses smell better than those with little noses?
- People have used dogs to find things for centuries, but scientists still don't completely understand why dogs are so good at using their noses.
Why is this difficult to understand?
Do all dogs have the same sense of smell, or do dogs with bigger noses smell better than those with little noses? People have used dogs to find things for centuries, but scientists still don't completely understand why dogs are so good at using their noses. Why is this difficult to understand?
OverviewImagine you're skiing the deep snow of a mountain pass when you hear a low rumble. The snow beneath you suddenly gives way. In a terrifying instant you realize you've been caught in an avalanche. A roaring sea of snow envelops you and you are buried under snow compacted as hard as concrete. Rescue must come fast. After only 30 minutes your chances of survival are 50 percent. If you are not equipped with an avalanche rescue beacon, your next best hope is a search-and-rescue (SAR) team working with avalanche rescue dogs. How can a dog pick up your scent through densely packed snow, recognize the scent as the important one, and then hone in on it? Part of the answer is the dog's olfactory system, which is 10,000 to 10 million times more sensitive than a human's. Dogs have about 220 million scent cells, compared to about 5 million in humans. Scent cells, or cilia, react to odor-carrying molecules that flow into noses. In dogs, these cells line the canine mucosa, a membrane at the rear of the snout which is folded so many times that, if smoothed out, it would be larger than the dog's body. When the hairlike cilia encounter an odor-carrying molecule, they trigger nerve cells that signal the dog's brain. It takes three to six years to teach a dog to track a human scent, for the dog must learn to pick up and follow an individual scent it hasn't smelled before, and do it in rough terrain amid distractions. The task is made more difficult when the victim is buried under an avalanche and has left no scent trail. Dogs can smell a buried person because our bodies constantly shed skin cells and give off odors in the form of gases. A person walking across the ground leaves these cells and odors in a scent trail the dog can follow. A person buried under snow leaves no such trail, but dogs use air scenting to smell the human odors, or gases, rising up through the snow. A dog searches an area until it finds the spot where the odors are strongest, then alerts rescuers by barking or digging. For dogs, tracking and searching is just a game. For the buried victim, it's a matter of life and death.
ActivityMany people believe dogs are the top smellers of the animal kingdom, although that has never been proven. Scientists do know that dogs smell much better than most animals, including humans. Researchers have also found that some dogs can smell better than others, even if they are of the same breed. How sensitive is your nose? Can you smell better than some other people? And how does your nose stack up against a dog's? To find out, try this smell sensitivity test. Materials
- glass measuring cup like those used for cooking
- bottle of white vinegar
- distilled water
- several clean, medium-sized glass jars
- masking tape
- At what dilution could you no longer smell the vinegar? Dogs can smell the vinegar down to about 10 dilutions, six or seven orders of magnitude weaker than humans. Why?
- Did anyone with a cold or allergies have a harder time smelling the vinegar? Why?
- There are some odors that some people can't smell at all, a condition called human specific anosmia. Is there anyone in your group who can't smell vinegar at all?
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Brook-field, CT: Millbrook Press.
Sachs, J.S. (1996, Mar) The fake smell of death: Synthetic corpse smell and
other scents help train search dogs. Discover, p. 86.
Whittemore, H. (1995) So that others may live: Caroline Hebard and her search
and rescue dogs. New York: Bantam Books.
Avalanche rescue dogs:
The Search and Rescue Society of British Columbia:
California Rescue Dog Association: