What makes dogs’ sense of smell so different from humans’? How do various animals use their sense of smell to navigate and survive?
In An Immense World, Ed Yong explores the fascinating ways animals perceive their environment through scent. From dogs detecting identical twins to elephants avoiding threats and seabirds mapping the ocean, the sense of smell in animals reveals capabilities far beyond human understanding.
Keep reading to discover the surprising truth about how animal and human noses compare, and why we might be better sniffers than we think.
The Sense of Smell in Animals
Yong says that the sense of smell in animals allows them to do several things that humans can’t do. They can detect prey, tell individual animals and humans apart, locate hidden objects, create mental “maps,” and much more.
For example, dogs perceive the world primarily through their sense of smell, which is much more advanced than humans’. Humans inhale and exhale a single flow of air for both smelling and breathing. In contrast, dogs’ noses split the airflow into two parts—one for breathing and one for smelling—so when they exhale, the smells they’ve inhaled stay inside their noses.
Because of their heightened sense of smell, dogs can tell identical twins apart by sniff, and can detect all kinds of things that humans can’t, such as tumors, land mines, and missing people. Dogs can even “see into” the past through smell, by detecting who’s been in a room, for example, or even what’s happened there.
Yong also cites elephants as having a highly developed sense of smell. In experiments, they consistently run from clothes worn by the Maasai people, who will sometimes spear elephants, but show little concern when they smell washed clothing or garments worn by the Kamba people, who are not a threat to elephants.
Seabirds such as albatrosses and shearwaters can “map” the vast, featureless ocean by using their sense of smell to detect where there are higher concentrations of dimethyl sulfide, or DMS. DMS is a gas released by plankton when it’s eaten by krill, which is food for seabirds. DMS tells the birds which parts of the ocean contain plentiful food sources.
| Comparing Animals’ Sense of Smell With Humans’ While animals can use their sense of smell to do many things humans can’t—and scientists have long believed that humans have an inferior sense of smell compared to many animals—recent studies show that humans’ sense of smell is superior to that of dogs and other animals, at least in some instances. Studies show that the human nose is more sensitive than some animals’ noses to odorants in bananas, flowers, blood, and urine, for example. Some scientists have theorized that this is because humans are better at detecting smells that are important to us (while this hypothesis makes some sense when applied to blood, it’s less clear when applied to the other aromas!). One study shows that humans are capable of following a scent trail in the same way that dogs can. The study’s human subjects got down on all fours wearing blindfolds and earmuffs, so as not to rely on their vision or hearing, and followed a string dipped in chocolate essence that researchers zigzagged across a field. While the humans weren’t as good at this task as dogs, they nonetheless could do it, and they got better at it quickly after a few weeks of practice. Scientists theorize that one reason humans can’t use our sense of smell to perform as many tasks as animals is simply that we don’t go around sniffing things all the time, as dogs do. In other words, behavior may play as big a role in scent as physiology (not to mention that humans rely more heavily on other senses, such as vision). |
