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Eileen bundles up to see how rescue dogs find people.
Segment Length: 8:00

Teacher's Guides Index

Avalanche Rescue
Show Number 1405

How do dogs find people buried
in an avalanche?

Why do some animals have
a better sense of smell than others?

[Apple Image] Getting Started

Put familiar substances with various odors into containers labeled with numbers. Herbs, spices, oils, and any other nontoxic substances that give off a distinctive odor will work. Smell each one. Write down what you think the odor is and how strong it is. Describe what each odor smells like (sweet, sour, like a flower or an old dishrag). Test your friends to see what smells they recognize. How good are you at identifying the substances? Does everyone describe odors the same way?

When an occupied building collapses, what is the first thing emergency crews do? How do they do it? What is the best way to find survivors in such a disaster? Would you use the same method if someone was buried under several feet of snow?

What kind of animal would be best for rescuing people who are lost or buried? What makes your choice ideal for such work?

[Apple Image] Overview

Imagine 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.

[Apple Image] Connections

  1. Do all dogs have the same sense of smell, or do dogs with bigger noses smell better than those with little noses?
  2. 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?

[Apple Image] Resources

Bulanda, S. (1994) Ready! A step-by-step guide for training the search and rescue dog.
Portland: Doral Publishing.

McClung, D. (1993) The avalanche handbook. Seattle: Mountaineers.

Ring, E. (1991) Search and rescue dogs: Expert trackers and trailers.
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:

Student Activity:
Avalanche Rescue
Catch A Whiff Image

Catch a Whiff of This

Smell different dilutions of vinegar to measure your odor sensitivity.

[Apple Image] Main Activity

Many 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.


1. Fill one glass jar with pure water and another with vinegar. Label the jars with a piece of tape and a marker. The water should not have an odor, while the vinegar will have its typical, distinct odor.

2. Put 1/4 cup of vinegar in another jar, then add 21/4 cups of water and mix the solution. The ratio will be 9 parts water to 1 part vinegar. Label this jar #1. Can you smell the vinegar?

3. Pour 1/4 cup of that 9:1 water/vinegar solution from jar #1 into a jar labeled #2. Add another 2 1/4 cups of water. You've just reduced the concentration of vinegar by an order of magnitude, making it ten times weaker. Can you still smell the vinegar?

4. Repeat step 3, this time pouring 1/4 cup of the diluted solution from jar #2 into a jar labeled #3. Add 21/4 cups of water to jar #3 and mix. You've reduced the concentration of vinegar by another order of magnitude. Can you smell the vinegar?

5. Continue the process until no one in the group can smell the vinegar.


  1. 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?
  2. Did anyone with a cold or allergies have a harder time smelling the vinegar? Why?
  3. 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?

[Try This]

Many search-and-rescue operations don't involve dogs. Talk to local police and volunteer search organizations about what skills people must use and what clues they look for when searching for someone.

[Try This]

Interview several dog trainers or police K-9 officers and find out what breeds they think make the best search dogs. Are different breeds better at finding certain things? What factors other than sense of smell do dog trainers look for?

[Try This]

Buy a small, solid air freshener and hide it in a room. Wait about a half hour, then bring a few friends in and ask them to find it, using only their noses. Does one person have a better sense of smell than the others? Do people become less sensitive to the smell as time passes?

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