Globio

A Scent-sational Sensory Organ

Some are cold and wet. Others are long and droopy. Some are so sensitive they can detect a drop of blood in 94 liters of water. They’re noses, a scent-sational sensory organ. A nose’s main job is to sense odors, but many noses also double as breathing tubes. Noses range in size from an elephant’s 2.1 m trunk to a whale’s blowhole, which is reduced to a flat nostril on top of its head. True noses—the fleshy, often pointy things that stick out from a face—are found in mammals. Fish, reptiles, birds, and insects don’t have true noses. Their scent-sniffing organs are in snouts, beaks, and antennae.

An elephant’s trunk does many things. Elephant’s have a great sense of smell but they can also raise their trunk as a warning, make a trumpeting call, or cheerfully greet a friend.

©G.Ellis/GLOBIO.org

The Structure of Noses

Many noses have a structure similar to the one on your face. The visible part of the nose is fleshy and sticks out from the front of the head. It is made of cartilage, which is more flexible than bone but stiffer than skin. Air enters the nostrils when it is breathed in. Inside the nose is the hollow nasal cavity that extends to the back of the throat. Air flows through the nasal cavity on its way to the windpipe and lungs. On the roof of the nasal cavity are two patches of special cells with millions of receptors that collect odor molecules. The molecules stick to the receptors and send information along the olfactory nerve to the olfactory bulb in the brain. The brain “reads” the smell, and the person or animal detects the odor.

The Best Nose for the Job

Not everything that looks like a nose is just a nose. What looks like an anteater’s long nose is a combination of its very long jaw and a nose at the very tip. They sometimes eat more than 30,000 ants and various insects each day. This anteater baby is learning from its mom how to become an expert ant eater.

©ZSSD/Minden Pictures

Not all noses follow the same model, but every nose is adapted to help an animal breathe or smell better in its environment. Whales don’t use their noses (blowholes) nearly as much to smell as they do to breathe. They can open and close their blowholes to shut out water when they dive. Beavers, manatees, and anteaters can also close their noses to keep out water or dirt. An anteater’s long, pointy nose is the perfect shape to poke into a termite mound. Then it can catch the insects exposed with its sticky tongue.

Nothing Smells Like a Fish

Fish don’t breathe air, but they do have nostrils. While a fish’s gills remove oxygen from the water for the fish to breathe, the nostrils serve only to collect scent from the water. Detecting scent is important to fish. They use scent to hunt, find food, and navigate. Which fish can smell a drop of blood in 94 liters of water? A shark.

It’s as Plain as the Nose on Your—Antennae?

Insect “noses” are located on their antennae. In the case of moths, each hair-like strand on its feathery antennae is a separate scent organ. Like fish, insects don’t breathe through their noses. Instead, they have round holes called spiracles along their bodies that allow air to move in and out.

Survival Scents

Ants, like other insects, don’t have noses. They have antennae that help them "smell" stuff by the chemicals things give off. Antennae are one of the most important parts of the ant’s body. Ants use their antennae to communicate and identify scents. These two ants are “smelling and talking” with their antennae.

©G.Ellis/GLOBIO.org

Detecting odors is a nose’s main job. But it’s not just a job—it’s a survival skill. Animals rely on scent to survive. In some animals the sense of smell is so strong that huge areas of the brain are devoted to processing it. For example, a bloodhound’s sense of smell is a million times more sensitive than a human’s. Animals use their sense of smell to track prey or avoid predators, find and follow trails, and detect when mates are receptive. They mark territory by leaving their scent behind in urine or by rubbing against something. Scent also plays a big part in how humans perceive taste. In fact, as much as 75 percent of what humans “taste” comes from the way food smells.

Insects also use scent to find food and mates and even to communicate with each other. Bees and ants can recognize members of their own colonies by scent and identify the odor of an intruder.

Filter and Recycler

Camels live in the desert where there is a lot of sand blowing around. The sand doesn’t bother the camels, though. They can open and close their nostrils to keep sand out, even on the windiest days.

©G.Ellis/GLOBIO.org

Noses also perform some extra breathing duties. As air moves through the nose and nasal passages, it is warmed and moistened. Bacteria and bits of dust and particles get trapped in the mucus inside the passages, and they get eliminated from the body when the mucus is swallowed. Some animals in dry climates can even remove moisture from the air as it is exhaled. The inside of a camel’s lungs is warm and moist. That precious moisture would be lost if it weren’t for the camel’s special nose. The moisture in the air the camel exhales gets trapped by the camel’s large nose and “recycled.” This helps the camel survive in its dry environment.

Pass the Salt

Some species of sea birds and reptiles have special organs that remove extra salt from the body. When they eat prey from the salty ocean, they ingest too much salt. The organs remove the salt and empty it as a liquid into the nostrils where it drips out. Gulls, penguins, marine iguanas, and sea turtles all have the ability to sneeze out salt.

Big Nose, Bigger Noise

Elephant seals were named after their large noses that look a little bit like an elephant’s trunk. Their noses might look like a trunk but they don’t work the same way. Only male elephant seals have big noses and they use them to attract females.

©K.Campbell/GLOBIO.org

Some noses are also for show—and tell. Male proboscis monkeys have huge noses compared with the females. One reason may be that females prefer big noses! But another possibility is that the size and shape of the nose make the monkeys’ honking call louder and lower. The enhanced honking may attract more females or warn off rival males. The large, fleshy nose of a male elephant seal is used both to enhance the sound of his roaring and to reclaim moisture while breathing.

Touchy-Feely Noses

Some noses double as feelers. Moles have special nerves in their noses that are very sensitive to touch. In an underground world, moles need to be able to feel their way, and their noses do the job. Pig noses are also sensitive and help them root tasty treats out of the ground.

This fruit bat has a nose that looks a lot like a leaf. In fact, the part is called a nose leaf. This bat eats fruit and insects. The nose leaf doesn’t help it smell better but it may help when it’s hunting insects.

©C.Ziegler/GLOBIO.org

The Nose Knows the Way

Many bats have special flaps of skin, called nose leaves, surrounding the nose. Bats use sound to find insect prey as they flit through the air in a process called echolocation. To do this they send out sound waves from their mouths or noses that hit insects and then bounce back, letting the bats know where the prey is. Scientists believe that nose leaves may focus or enhance the echolocation waves the bat sends out.

Extra Help Packed in a Trunk

The nose that does the most extra duty is the elephant’s trunk. It is a strong, flexible limb that the animal can use to pick up small objects or pull down trees. Elephants can also suck water into their trunks to drink or spray on themselves to cool off.

Sniffing out Danger and Disease

You’ve probably heard of dogs that sniff out dangerous things or track lost people. But dogs may also be able to smell disease. Dogs have shown the ability to detect skin cancer cells and even identify cases of lung and breast cancer by sniffing a patient’s breath. But dogs aren’t the only super sniffers. In Mozambique, trained rats have proven to be excellent at sniffing out landmines, buried bombs that threaten anyone who steps on them. The rats make good mine finders because they are too lightweight to set off a mine. When a rat detects a mine, it scratches the ground, letting its handler know where the mine is located.

Rats can smell much better than humans. Almost every living and non-living object has a scent and a rat uses this scent information to identify and find things. Rats, of course love the scent of food.

©M.Durham/GLOBIO.org

How to Build a Better Nose

Humans may never be able to smell as well as a dog, but that doesn’t stop people from trying to invent a better nose. Uses for electronic noses include finding harmful bacteria, revealing spoiled food, locating bombs, and even monitoring air quality in space. The ENose was developed by NASA to sniff out ammonia leaks on the International Space Station. The ENose can detect many different odors. Someday it may go to work monitoring for the presence of poisonous gases here on Earth. Or it could sniff its way along as part of an exploration team that travels to the Moon or a planet. In May of 2007, British scientists discovered that coating the sensors of electronic noses with artificial mucus improved their ability to detect odors. Unlike the human nose, the artificial noses don’t need tissues!