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  • For humans, the concept of smell is a bit intangible. Sure our noses can identify milk

  • that's gone bad or a batch of cookies fresh from the oven.

  • The human nose can identify some 1 trillion smells, but it's just not that impressive

  • compared to many members of the animal kingdom.

  • Take the elephant, for example, that trunk isn't just for grabbing peanuts, it's sniffer

  • is so powerful it can smell water from miles away. The trunks are also wildly multifunctional;

  • as a straw,

  • a dexterous limb, a vibration sensor, and of course, a trumpet.

  • Alright, you guys ready?

  • Which kind of begs the question, what is a nose? This isn't technically a nose.

  • It's more of a bony horn.

  • This is a nose, but it's also a voice amplifier and somehow, a feature for attracting mates.

  • So by definition a nose just has to be a part of a face or facial region that contains nostrils

  • and the organs of smell.

  • After that noses vary wildly in both aesthetics and function.

  • Now I want to talk about a nose that is not only highly sensitive, but also has the impressive

  • ability to remember smells over long periods of time.

  • They also might be the cutest... I'm talking about dogs.

  • This is my dog Henry.

  • I think he's a chihuahua toy fox terrier mix, but he loves treats.

  • There you go.

  • But when I hold this treat up for him, Henry's not just smelling like

  • "yep, that's a treat."

  • He's smelling in layers, so Henry's smelling the wheat flour, the chicken, the yeast that

  • make up this treat, all separately.

  • This is why dogs can detect illegally smuggled items buried in luggage and can even find

  • people buried in avalanches.

  • So how does this work.

  • Well, it all comes down to the structure of the nose and the sensory abilities of the

  • brain, when Henry inhales his nostrils pull in air packed with molecules that contain smells.

  • A fold of tissue just inside his nostrils separates the airflow into two paths, one

  • for olfaction or smells, and the other one for respiration.

  • This prevents the dog from immediately breathing out to smell like we do.

  • When they do exhale air exits through different slits in the sides of their nose.

  • This helps pull new odors into the nose through the nostrils and allows the dog to sniff practically

  • continuously.

  • It also helps the dogs can identify which nostrils smell came through, so that they

  • can locate which direction the smell is coming from.

  • Pretty helpful for early dogs that needed

  • to hunt prey in the wild, or in Henry's case, finding the treats I've been hiding around the

  • house.

  • After inhalation and separation from the air going to the lungs, a small amount of air

  • passes over turbinates.

  • Turbinates are these plates of bony structures that contain scent-detecting cells.

  • There's even a separate section called the vomeronasal organ, which is used primarily

  • for social interactions.

  • So, mostly for sniffing butts.

  • Dog noses are thought to contain roughly 40 times the number

  • of smell receptors that humans have.

  • More if you're looking at a highly sensitive dog like a bloodhound.

  • All dogs have talented sniffers, but it's a spectrum, some breeds are definitely

  • better than others.

  • Bloodhounds actually have more scent receptors than most dogs.

  • They also have other features that make them the famous nose-with-a-dog-attached.

  • In fact, those skin rolls that make bloodhounds so unique, actually help them trap and collect

  • scent particles.

  • From here, the detected smells are converted into nerve impulses and sent

  • to the olfactory bulb in the brain.

  • Within the olfactory bulb, an odor image is created,

  • combining all the individual smells into a cohesive identifiable one.

  • This is what helps dogs retain memories of scents for very long periods of time.

  • There's another characteristic of a dog's nose that makes it unique; the wet and coldness of it.

  • This is called a rhinarium, and it's that furless skin at the end of a nose.

  • Now scientists aren't exactly sure what function is serves.

  • Recent research suggests that it serves as a thermal radiation detector helping dogs

  • sense heat.

  • It could also just help scent molecules stick to the nose.

  • I just want to eat you up.

  • What do you think of that?

  • As a vet I often get asked if a dry nose is a sign of illness.

  • I tell them it can vary from species to species and just because your dog's nose is dry at

  • that time it doesn't necessarily mean that something we need to be concerned about.

  • These highly sensitive noses combined with their ability to be highly trained makes dogs exceptional

  • companions for jobs that require an acute sense of smell.

  • I spent time with some of the best working with the Wildlife College and the Ivan Carter

  • Wildlife Conservation Alliance in South Africa.

  • They use bloodhounds trained at a very young

  • age to track poachers in national parks and there's even a dog that tracks orphan baby

  • rhinos, so these guys can be rescued and protected.

  • Without these dogs we would catch poachers 4 to 6% of the time, implementing these

  • dogs where they're finding poachers 75 to 80% of the time, and they often catch them before

  • rhinos been killed.

  • Thanks to their incredible noses, we've been able to protect hundreds of animals from poachers

  • and rescue several baby orphan rhinos too.

  • Thanks for watching our new series Tusks to Tails.

  • I'm Dr. Evan Antin, with my dog Henry, and if there's an animal you would like us to

  • feature, please leave it in the comments.

  • We'll see you next time.

For humans, the concept of smell is a bit intangible. Sure our noses can identify milk

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Why Your Dog Can Remember Smells and You Can't

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    林宜悉 posted on 2021/01/12
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