Bigger and Better People have a pretty good sense of smell. Yet it’s nothing compared to many animals. Take a bloodhound. T is kind of dog is famous for using its nose to track lost people. T e dog’s olfactory system works the
same way as people’s. It’s bigger, though. T e spot where odors stick is about the size of a crumpled napkin. About 230 million smell receptors grab smells. T at’s 40 times more receptors than people have. A bigger part of the dog’s brain identifies smells, too. Many other animals have a better sense of
smell than people. Some use their noses. Some don’t. Let’s see how these super sniff ers work.
Finding Food A polar bear points its nose to the sky and sniff s. Suddenly, it catches a whiff of a seal. T e seal is nowhere in sight. It’s a kilometer
away and swimming below ice that’s almost 2 meters thick. T e bear follows the smell. Soon, it reaches
the seal’s breathing hole. T e bear lies by the hole in the ice. It waits and watches the water. Finally, the seal needs oxygen. It rises close
to the surface. A blast of seal breath bubbles up. T at’s the sign the bear needs. It plunges a paw into the water. T e bear grabs the seal with its claws and drags it onto the ice.
DANGER ALERT!
The nasal cavity of a rhinoceros is bigger than its brain. It uses smells to sense predators.
6 NATIONAL GEOGRAPHIC EXTREME EXPLORER
Star Nose A kind of mole uses air bubbles to find food, too. T is mole oſt en hunts underwater. As it swims, it blows out air bubbles. It makes as many as 10 air bubbles per second. Some bubbles bump a small fish. T e air
inside these bubbles picks up a fishy smell. T e mole quickly sucks the air bubbles back into its nose. Now the mole can smell the fish. It can’t see the fish, though. T is mole is nearly blind. So it follows its nose. When it reaches the fish, the mole uses its
nose in a diff erent way. Its snout has 22 red, wiggly tentacles. T e mole uses its tentacles to grab the fish and pull it into its mouth.
The Way Home Some animals use their noses to do more than sniff out food. T ey use their sense of smell to find the way home. T at’s what a salmon does. T is fish hatches in a freshwater stream. It
memorizes the smells there. T en it sets off on a long adventure. It swims 1,600 kilometers to the ocean. Aſt er up to 5 years at sea, it heads back to the stream to lay its eggs. T e journey is hard. T e salmon swims
upstream. It jumps up waterfalls and past hungry bears. Finally, it sniff s a mix of rotten plants, dust, and insects. It remembers these smells. T e salmon followed its nose home.
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