Does Your Dog’s Nose Work Better Than a Grizzly’s?

Imagine a proud new dog owner bragging up their new pup—a hound like Mingus or a retriever like Snort.

“My dog has a better nose than a grizzly bear,” he or she boasts.

Should you believe them? After all, from the outside, a dog’s and a bear’s noses look very similar. Humans have bred dog specifically to trail scent. A bloodhound, for example, can detect odors several times more acutely than a run-of-the-mill pound puppy.

But can a dog out-sniff a bear? Science says no. Not even close.

Let’s be clear. A dog’s nose is superhuman. As we’ve established elsewhere, a trained dog can not onlysmell a fish in a stream, but can distinguish between species of fish—by scent alone. But even a bloodhound’s snozzle wilts before that of a grizzly bear.

From the perspective of hardware, dog and bear noses are somewhat similar. They have large nostrils, hundreds of tiny muscles for manipulating those nostrils, a snout for taking in and circulating air, and glands for keeping those receptors moist.

But the software makes all the difference. That is, the animals’ neurology. The late brain surgeon George Stevenson made a hobby of studying bear brains after he retired from studying humans.

“These bears are amazing creatures,”Stevenson once said. “I believe they have the most impressive olfactory system of any animal on the planet. Their nose is the very best.”

Stevenson and his colleague scientists havestudied bear brainsusing medical radiology, including MRI machines. They’ve also made detailed models of bear brains by filling empty bear skulls with a special type of wax.

Many mammals have specialized parts of their brain called “olfactory lobes” that interpret scent. Humans have an olfactory lobe about the size of an eraser on the end of a pencil. Dog olfactory lobes are larger. Bears, however, are in a class of their own. They have two olfactory lobes, each about the size of your thumb.

That’s even more impressive when you consider that bear brains are a third the size of a typical human brain, meaning that, relatively speaking, even more brainpower is dedicated to interpreting the world via smell.

Quantifying olfactory power is very difficult and requires some interpretation. But, according to Stevenson, a typical dog’s nose is about 100 times better than a human’s. A bloodhound, perhaps 300 times better. But a grizzly’s nose packs at least seven times more sniffing power than even a bloodhound’s—perhaps 2,000 times better than a human. Besides the olfactory lobes in the bear’s brain, the snout itself contains two, 9-inch channels, each with 10 million nerve strands and billions of receptors shooting information into the animal’s brain.

Bears live and die by their noses. A bear emerging lean and hungry during springtime on a mountainside must smell a carcass or distant green-up miles away in order to survive. A griz looking for a mate must locate a potential partner across entire mountain ranges, and scent is the most efficient way to do so. Over the eons, nature has favored bears with good olfactory power to eat better, live longer, and breed more often, passing on their genes.

Dogs have some catching up to do.

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