Tag: Dog’s nose

Yet another bonus of having dogs in our lives.

There really is no end to the sense of smell that a dog has.

I was browsing online The Smithsonian magazine and came across a long article that was all about the dog’s sense of smell in terms of sniffing out citrus greening disease.

There’s no end of articles about the dog’s sense of smell and I have written about it before. But first I’m going to reproduce the article on Animal Planet because it gets to the point.

Dogs rule. Or, at least, they do when it comes to their sense of smell, which crushes that of humans. According to the Alabama Cooperative Extension System (ACES), a dog’s sense of smell is about 1,000 times keener than that of their two-legged companions — and many dog experts claim it’s millions of times better — thanks to the construction of their often-slobbery, wet schnozzes. So what, exactly, is going on in there?

A dog sniffs at scents using his nose, of course, and also his mouth, which may open in a sort of grin. His nostrils, or nares, can move independently of one another, which helps him pinpoint where a particular smell is coming from. As a dog inhales a scent, it settles into his spacious nasal cavity, which is divided into two chambers and, ACES reports, is home to more than 220 million olfactory receptors (humans have a measly 5 million). Mucus traps the scent particles inside the nasal chambers while the olfactory receptors process them. Additional particles are trapped in the mucus on the exterior surface of his nose.

Sometimes, it takes more than one sniff for a dog to accumulate enough odor molecules to identify a smell. When the dog needs to exhale, air is forced out the side of his nostrils, allowing him to continue smelling the odors he’s currently sniffing.

Dogs possess another olfactory chamber called Jacobson’s organ, or, scientifically, the vomeronasal organ. Tucked at the bottom of the nasal cavity, it has two fluid-filled sacs that enable dogs to smell and taste simultaneously. Puppies use it to locate their mother’s milk, and even a favored teat. Adult dogs mainly use it when smelling animal pheromones in substances like urine, or those emitted when a female dog is in heat.

Top Sniffers

What all of this sniffing and processing really means is that a dog’s sense of smell is his primary form of communication. And it’s a phenomenal one, because dogs don’t just smell odors that we can’t. When a dog greets another dog through sniffing, for example, he’s learning an intricate tale: what the other dog’s sex is, what he ate that day, whom he interacted with, what he touched, what mood he’s in and — if it’s a female — if she’s pregnant or even if she’s had a false pregnancy. It’s no wonder, then, that while a dog’s brain is only one-tenth the size of a human brain, the portion controlling smell is 40 times larger than in humans.

So, who’s top dog when it comes to sniffing? While all canines have an incredible sense of smell, some breeds — such as bloodhounds, basset hounds and beagles — have more highly refined sniffers. This is a result of several factors. Dogs with longer snouts, for example, can smell better simply because their noses have more olfactory glands. Bloodhounds, members of the “scent hound” canine group, also have lots of skin folds around their faces, which help to trap scent particles. And their long ears, like those of Bassets, drag on the ground, collecting more smells that can be easily swept into their noses.

Of course, dogs are individuals as well, so it’s certainly possible to find a non-scent-hound who can outperform one. And as Dr. Sandi Sawchuk, a clinical instructor at the University of Wisconsin School of Veterinary Medicine, notes: “There are lots of breeds that can be trained to sniff out certain items — for example, cadaver-sniffing dogs, drug-sniffing dogs, etc.”

Now to that longer Smithsonian article.

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Can Disease-Sniffing Dogs Save the World’s Citrus?

Once trained, canines can detect citrus greening disease earlier and more accurately than current diagnostics

By Katherine J. Wu ,    smithsonianmag.com
Feb. 3, 2020

A detector dog named Szaboles, trained to sniff out the bacterial pathogen Candidatus Liberibacter asiaticus in a citrus orchard. (Courtesy of Tim R. Gottwald)

Tim Gottwald will never forget the sight: the mottled yellow leaves, the withered branches, the small, misshapen fruits, tinged with sickly green. These were the signs he’d learned to associate with huanglongbing, or citrus greening—a devastating and wildly infectious bacterial infection that slashed the United States’ orange juice yields by more than 70 percent in the span of a decade.

“It’s like a cancer,” says Gottwald, a plant pathologist with the United States Department of Agriculture. “One that’s metastasized, and can’t be eradicated or cured.”

Once they’ve begun to sport splotchy foliage and stunted fruit, trees can be diagnosed with a single glance. A symptomatic plant, Gottwald says, is a diseased one. Unfortunately, the converse isn’t true: Infected trees can appear normal for months, sometimes years, before visibly deteriorating, leaving researchers with few reliable ways to suss out sick citrus early on—and giving the deadly bacteria ample opportunity to spread unnoticed.

Now, Gottwald and his colleagues may have a creative new strategy to fill this diagnostic gap—one that relies not on vision, but smell. They’ve taught dogs to recognize the telltale scent of a huanglongbing infection—an odor that eludes the attention of humans, but consistently tickles the super-sensitive schnozz of a mutt. Once trained up, canines can nose out the disease within weeks of infection, trouncing all other available detection methods in both timing and accuracy, the researchers report today in Proceedings of the National Academy of Sciences.

“This is a major step in the development of what could be a really important early detection tool,” says Monique Rivera, an entomologist and citrus pest expert at the University of California, Riverside who wasn’t involved in the study. “It could give growers information about potential exposure … to the causative bacteria.”

First described in China in the early 1900s, huanglongbing has now crippled orchards in more than 50 countries around the globe. Fifteen years ago, the scourge took hold in Florida, where infected trees are now the norm; the state’s $9 billion citrus industry, once the second largest in the world, is now on the verge of collapse. From oranges to grapefruits to lemons, no variety of citrus is immune.

As the disease continues to creep into new regions, researchers worldwide are scrambling to contain it. But the task has proved difficult: No effective treatments, cures or vaccines exist for huanglongbing, the product of a bacterium called Candidatus Liberibacter asiaticus (or CLas, pronounced “sea lass”) that’s ferried from tree to tree by winged insects. Scientists have also found the microbes to be extraordinarily difficult to grow and study in the lab.

The 20 canines in the study trained to detect CLas-infected citrus trees. (Gottwald et al., PNAS, 2020)

Currently, the only surefire way to curb citrus greening’s spread is to extract and eliminate infected trees. This strategy depends entirely on early detection—“one of the biggest problems in the field right now,” says Carolyn Slupsky, a plant pathologist at the University of California, Davis who wasn’t involved in the study. Spotting an asymptomatic infection by eye is essentially impossible. And though genetic tests can sometimes pinpoint microbes in apparently healthy trees, their success rates are low and inconsistent, due in part to the patchiness with which CLas distributes itself in plant tissue.

In many ways, huanglongbing is “the perfect storm of a disease,” Slupsky says.

But canines may just be the perfect candidates to lend a helping paw. With a sense of smell that’s 10,000 to 100,000 times more powerful than a human’s, dogs are superstar sniffers, capable of nosing out everything from bombs to drugs. In recent years, they’ve even been deployed to detect pathogenic diseases like malaria. Infections, it turns out, stink—and dogs definitely take notice.

To see if pooches’ powers of perception might extend to huanglongbing, Gottwald and his team taught 20 dogs to pick up on the smell of citrus plants with known infections, rewarding the pups with toys when they identified the correct trees. After just a few weeks of training, the newly-minted citrus sniffers were picking out infected trees with about 99 percent accuracy. Put in pairs to corroborate each other’s results, the dogs got close-to-perfect scores.

Gottwald was floored. “I wasn’t surprised [the dogs] could do it,” he says. “But I was surprised by how well they could do it. It was pretty amazing.”

The team then pitted the pups against a common but expensive laboratory test that’s often used to verify the presence of CLas DNA in suspicious-looking citrus. After spiking the microbes into 30 trees, the researchers mixed the newly-infected plants into rows of healthy ones and allowed the dogs to inspect them on a weekly basis. Within a month, the canines had collectively homed in on every single CLas-positive plant.

The DNA test, on the other hand, had no such luck: Seventeen months into the infection, it was still failing to identify a third of the diseased trees.

If Gottwald’s team sees continued success, “this could be very exciting for [citrus] growers,” who could someday keep dogs around as a fast and relatively inexpensive way to survey their orchards, says Phuc Ha, a microbiologist at Washington State University who wasn’t involved in the study. For now, the most immediate applications lie in disease prevention. But, she adds, should researchers develop treatments for huanglongbing, canines could eventually play a role in curing the condition as well.

Gottwald and his team have already begun to send small teams of citrus-sniffer dogs to inspect vulnerable trees in California and Texas. In both locations, the canines have alerted the researchers to trees that have yet to test positive in the lab.

This, however, evokes the double-edged sword of early detection research: The dogs are so much faster at finding potentially diseased trees that their picks can’t actually be confirmed, Slupsky points out. Maybe they’re more sensitive than the molecular test, and the disease is more widespread than researchers feared. Or maybe the canine’s noses are leading them astray. “Specificity is always an issue,” Slupsky says, “because you’re comparing them to an imperfect test.”

Dogs also come with their own drawbacks. They can tire; they can be distracted. They’re not machines. And while they can make fast work of orchards where infections are rare, their performance will probably plummet in heavily afflicted groves. In an ideal world, Slupsky says, the dogs would serve strictly as a first line of defense, screening trees for further monitoring or testing in the lab. She and her colleagues are hard at work on one such diagnostic, built to detect the unique suite of chemicals infected leaves produce early on.

Many questions remain unanswered. Gottwald still isn’t sure what exactly the dogs are smelling on the plants, though a series of experiments indicate the scent is probably coming from the CLas bacteria themselves. That theory may be tough to test: Though researchers like Washington State’s Ha have now grown CLas in the presence of other microbes, no one has yet managed to isolate the strain in a pure culture, hampering efforts to understand its basic biology and develop precise treatments.

While exciting, the team’s dog-nostic developments ultimately underscore “just how distant we still are from understanding a lot of the mechanistic processes that are going on [with this disease],” Rivera says. But with more collaboration and multidisciplinary work, she adds, “I think we’ll keep heading toward solutions.”

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When one watches a dog closely it’s very clear that their nose is their primary sense. At least a thousand times better than our human sense of smell and some people put it much higher. That is impossible to understand. The best we can do is to wonder at the sort of world that dogs ‘see’ with their noses.

I will close with an old photograph of Pharaoh helping a prospector look for gold in our creek.

Pharaoh, instinctively, thought that a dog’s nose would raise the odds of a find.

A nose for doing good work!

A dog’s nose, of course!

We all know how good are the noses of our dogs. Yet, I suspect, many do not know how truly good is that nose. The Science ABC site has a detailed account of Why Do Dogs Have Such A Great Sense of Smell?
Here’s part of that article:

Dog Nose vs. Human Nose

When we try to smell something, we inhale air with our nose and we use the same passage in our nose to exhale that air. Therefore, all the smell that we get when we are inhaling is lost when we exhale that air. However, a dog has two different air passages, one for breathing and another for smelling. This means that dogs are able to store the smell in their nose even while breathing out the air!

When dogs exhale, they send air out through the slits of their nose, but the manner in which this air is exhaled through their nose helps the dogs to draw in new odor molecules. This also helps dogs capture more smells when sniffing.

You must have noticed that dogs’ noses are always wet, but have you ever wondered why? The mucus on the dog’s nose helps it smell by capturing scent particles. A dog also has the ability to smell independently from each nostril, this helps the dog to understand from which direction the smell is coming.

The passage through which dogs smell the air contains highly specialized olfactory receptor cells, which are responsible for receiving smells. A dog contains about 225-300 million smell receptors, as compared to just 5 million of these receptors being present in a human nose.

Dog Brain vs. Human Brain

By now, we clearly know that dogs have a nose that can smell about 1,000-10,000 times better than a human, but how are dogs able to remember all the different smells that they have sensed throughout their life?

The answer lies in the difference between the brains of dogs and humans. A human brain has a larger visual cortex than dogs, whereas a dog’s brain has a much larger olfactory cortex than humans. The visual cortex is responsible for processing visual information, whereas the olfactory cortex is responsible for processing the sense of smell. A dog’s olfactory cortex is about 40 times larger than that of a human.

Read the full science article here.

All of which makes a slightly longer introduction than normal to a fascinating article over on Mother Nature Network published two days ago.

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5 ways dogs are used for species conservation

May 16, 2017 Jaymi Heimbuch

Photo: Jaymi Heimbuch

Working dogs are an amazing asset not only for people, but for wildlife, endangered species and even threatened habitats. Expanding on the skills dogs have for tracking down scents and guarding something important, we humans have enlisted their help in many ways for conservation.

Here are five ways dogs are contributing to environmental protection efforts.

Smell for scat

It’s amazing the amount of information that can be sussed out of an animal’s poop. We can determine diet, health, genetics — even whether or not an animal is pregnant. Scat is really important to biologists studying elusive, sensitive or endangered species. Putting dogs on the track is an ideal solution.

Take cheetahs, for example. Scientists in Africa are using dogs and their unparalleled sniffing power to find cheetah poop, all in an effort to get an accurate count on the endangered big cats. (Only 7,000 cheetahs are left in the African wild, according to estimates.) And it’s working. Two trained dogs found 27 scats in an area of 2,400 square kilometers in western Zambia, according to a study published in the Journal of Zoology. Humans, looking for cheetah tracks over the same area, found none.

Groups like Conservation Canines (a handler and dog from the program pictured above), Working Dogs for Conservation and Green Dogs Conservation specialize in this area. Conservation Canines rescues highly energetic, “last chance” dogs from shelters and trains them to track down the scat of dozens of species, from wolves to moose to owl. Even things that are nearly impossible for humans to find — the minuscule scat of endangered pocket mice or orca scat floating on the ocean surface — dogs can track down. They are able to make huge contributions to scientific studies, all without ever bothering the wildlife being studied.

Sniff out problems for wildlife

Whether it’s sniffing out invasive species like giant snails in the Galapagos or detecting disease in beehives, dogs’ noses can be put to work in searching out what shouldn’t be there so that humans can act.

Dogs are able to sniff out particular plant species, pointing ecologists to tiny patches of invasive mustard so that the plants can be removed before they take over an area.

Conversely, dogs can sniff out rare or endangered native plants so that the species can be protected. Rogue is one such dog. The Nature Conservancy writes, “The 4-year-old Belgian sheepdog is part of a Nature Conservancy collaborative project to test the efficacy of using dogs to sniff out the threatened Kincaid’s lupine. The plant is host to the endangered Fender’s blue butterfly, found only in Oregon’s Willamette Valley.”

Surveying for the plant species is difficult work for people. It can only be done when the plant is in bloom so people can visually identify it. However, dogs like Rogue can sniff out the plant even when not in bloom, which can potentially double the length of the field season.

“More refined regional mapping of Kincaid’s lupine could promote the butterfly’s recovery and delisting — and contribute to larger habitat goals and wildlife impacts.”

Track down poachers

The trade in rare or endangered wildlife is a lot tougher for traffickers thanks to wildlife detector dogs. Trained to smell anything from tiger parts to ivory to South American rosewood, dogs are used in shipping ports, airports, border crossings and other locations to sniff out smuggled products.

It doesn’t stop there. Trained dogs can lead rangers to armed poachers in the wild, tracking down the culprits over long hours through heat and rain. They can catch poachers in the act, rather than just the products.

“Canine sleuths aren’t limited to the plains of East Africa, either,” reports National Geographic. “In the Democratic Republic of the Congo, bloodhounds are assisting in the fight against poaching in forested Virunga National Park, where the world’s last remaining mountain gorillas live. In South Africa, Weimaraner and Malinois dogs are helping to find wounded animals and track poachers on foot through the reserves around Kruger National Park.”

Guard endangered species

Dogs are also useful in putting their protective nature to use for endangered species.

Livestock protection dogs are trained to keep predators like cheetahs, lions and leopards safe, which then reduces conflict between ranchers and big cats and minimizes the instances of snaring or retaliatory killing of big cats. Cheetah Conservation Fund has a successful livestock protection dog program, which places Anatolian shepherd and Kangal dogs with ranchers. That not only has significantly reduced the number of livestock killed by predators but is also improving the attitude of local people toward cheetahs.

Sometimes the dogs are put to work guarding the endangered species themselves. One such successful program uses Maremma shepherd dogs to protect colonies of little penguins from foxes.

Keep bears wild

Karelian bear dogs are trained to keep bears from becoming too comfortable around people. A program by Wind River Bear Institute named Partners-in-Life uses a technique called bear shepherding. This specialized breed of hunting dog is used to scare bears away, and are an important part of the “adverse conditioning” work that keeps bears from becoming habituated. The ultimate goal is to protect bears from becoming habituated, a problem that leads to their being relocated or euthanized.

“Our Wind River Bear Institute mission, with the effective training and use of Karelian Bear Dogs, is to reduce human-caused bear mortality and conflicts worldwide to ensure the continued survival of all species of bears for future generations,” states the program.

This list is only a handful of ways that dogs help us with environmental conservation every day. More and more, we are figuring out new ways to put their skills to work, and more and more the dogs are proving they’re ready for the task!

Editor’s note: This story was originally published in July 2016 and has been updated with more recent information.

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Closing words from that Science ABC piece:

A dog does not care how you look or dress, but if he gets good vibes from your smell, then a dog will love you. The world is truly a better place because of these wonderful creatures that we are lucky enough to welcome into our lives.

Why not make the world smell a bit more beautiful for them?

Belay that!

Closing picture taken from the OregonLive website. A stunning picture of the “Fender’s blue butterfly, found only in Oregon’s Willamette Valley.”