[INTRO ♪] When we need a little help sniffing something
out, we usually turn to our furry best friends. And there’s good reason for that: dogs are
relatively easy to train, and their sense of smell is as much as 100,000
times more acute than ours. And they’re cuter. We have machines, sure, but electronic odor
detectors tend to struggle when the chemical of interest
is in low concentrations in a complex mixture of molecules, like, I
don’t know, the air. So we’ve taught dogs how to sniff out everything from sewage leaks to artwork-destroying
insects. But they’re not the only critters whose
sense of smell can be put to good use. There are other champion sniffers that we
could use to detect everything from disaster survivors
to gourmet fungi. Here are six of the animal kingdom’s most
useful noses. Truffles—the edible fungi that grow underground, and
not the chocolates— are a gourmet food that can fetch extremely
high prices. Since they’re very hard to cultivate, they’re
usually gathered from the wild. But finding fungi growing up to a meter underground
is pretty challenging. Luckily, pigs are here to help us sniff them
out, and they have for centuries. Pigs have over a thousand olfactory receptor
genes in their genomes— that’s more than dogs, or us, so they’re
able to detect a wider variety of smells. And their olfactory bulb— the part of their brains that processes the
information from smelling— make up about 7% of their brain. Your bulb is a mere 0.01% of your brain. But the real reason we use them to hunt truffles is that they seem to have a weird natural
affinity for them. In the 1980s, researchers discovered that
truffles contain large amounts of a musky steroid that boars secrete in their
saliva to put their sows... in the mood. So, many think that’s what attracts the
pigs. But a study in 1990 suggested another compound— dimethyl sulfide—was the odor instead. And there hasn’t been much follow up, so
the jury is still out. Either way, pigs’ natural instinct to root
around in the dirt in search of food probably enhances their
truffle-finding skills. Though, apparently, the pigs are notorious
for snacking on the goods they find, and it’s no picnic trying to wrestle a $1000
fungus from a 200-kilogram hog. Which is probably why nowadays, they’re losing their truffle hunting jobs
to trained dogs. I guess natural talent just doesn’t trump
canine ease of use. Detecting sick animals could help predict
and track outbreaks of diseases like bird flu that can
jump from other species to our own. But classic methods for detection, like blood
tests, require a lot of time and money for sample
collection and analysis. And why do that, when there’s a living disease
detector right under our noses? Enter: Mice. Like dogs and pigs, rodents have far more
functioning genes for odor reception than we do, so they’re
able to distinguish between scents that we can’t
even smell. And, relative to the size of their brains, their olfactory bulb is 200 times bigger than
ours, and 5 times bigger than dogs’. That, and their ease of breeding and care, makes them ideal for use as biosensors: living
chemical detectors. In a 2013 study, researchers found that mice
could sniff the difference between the poop from healthy mallard ducks and poop from ones infected with avian influenza. The six trained mice managed to pick out the
right poop about 80% of the time, though that was under lab conditions— it remains to be seen if they fare as well
in the field. But that hasn’t stopped New York scientists
from trying to take the whole mouse biosensor idea to the next
level using genetic engineering. In 2016, they showed their “MouSensor" mice, which are engineered with additional olfactory
receptor genes, can be up to one hundred times better than
regular lab mice at detecting particular smells—and those
were just the pilot versions. With results like that, it might not be long before dogs start losing ground to super sniffing
genetically modified mice. Landmines left behind after conflicts kill
thousands of people every year, but finding and removing them is a dangerous
and difficult task. It’s much safer for the humans involved
if something smaller and lighter can go through and flag where all the bombs
are first. People have used dogs for this, but they’re
expensive to train, and hard to transport around the world. So, a Belgian nonprofit enlists local noses
instead— those of Gambian pouched rats. These so-called rats—which are actually
members of a different rodent family—are huge rodents
native to central Africa. They can be 75 centimeters from nose to tail
and weigh over a kilogram. Their vision is terrible, but they make up
for it with an amazing sense of smell, which they use to communicate with each other
over long distances. And that means their noses have no trouble
detecting small amounts of explosives like TNT, even
if said explosives are buried 20 centimeters below ground in
a land mine. They’re also light enough to walk across
minefields safely, and they’re fast— a single rat can check 200 square meters in
20 minutes, which would take a person days to do. The nonprofit calls their trained rodents
“HeroRATS”—and it’s easy to see why. Gambian pouched rats helped clear over 13,000
mines in Tanzania, Mozambique, Angola, and Cambodia between 1997
and 2015. But the rats do require a rigorous training
protocol that takes the first nine months of their
eight-year lives. At least they look super cute in their special
little harnesses! After a disaster like an earthquake, finding victims trapped in debris can be a
slow, challenging process. Search and rescue dogs and their powerful
sniffers are a big help. But often, a smaller, more agile critter would
be even better. Something like … a search and rescue cat! Okay, cats aren’t actually being trained
to do this yet, but experts argued in a 2017 paper that maybe
they should be. That’s because, although we don’t know
as much about their sense of smell as other animals, what we do know suggests
they’ve got great noses. For example, they have 30 variants of the
V1R odor receptor gene— dogs only have nine, and we only have two. That suggests that they may be even better
than dogs at discriminating between some scents. The scientists behind the 2017 review argue
that this means they could take over some of the scent-related jobs that
dogs are trained to do now. And since cats are better climbers and can
squeeze into smaller spaces, they might be better suited to searching for
trapped people than man’s best friends. The problem is training them, but the researchers
believe it’s possible, with proper socialization and the right rewards
to motivate them. I mean, if we can train pigs and mice and
giant rats, how hard could cats be? Though, that saying about herding cats does
exist for a reason. So whether cats will live up to their heroic
potential remains to be seen. When you’re sick, you actually smell a little weird. No offense. The illness and your immunological reaction
to it alter the concentrations of some molecules
in your bodily fluids. I mean, you might not smell the difference,
but bees can. Though they don’t have noses in the way
we think of them, honey bees do have an amazing sense of smell. That’s what allows them to sniff their way
to food even if it’s miles away. And scents play incredibly important roles
in bee social lives. Which is why, in their genomes, they have
163 functional odorant receptor genes—the smelling genes
unique to insects. Fruit flies, for comparison, which also have
to sniff out their meals, have less than half that number. These diverse odor receptors allow bees to
smell the difference between subtly different varieties of the
same plant. And it only takes a single encounter with
an odor associated with a reward, like nectar, for a bee to be able to identify
the smell again. That makes it really easy to teach bees to
detect a variety of chemicals, including disease-specific odors on our breath. A designer in the UK even invented a glass
apparatus that allows for diagnosis by bee. The bees have to be trained on the smell of
the disease in question, but if a person with that condition breathes
into the device, the trained bees swarm towards their breath. If they’re not sick with the target illness,
the bees don’t react. It’s just a prototype, but it did work at
least once, identifying a confirmed case of diabetes. And sure, dogs can perform a similar trick,
but the bees are a lot easier to train. It only takes about 10 minutes of training
to get 98% accuracy from the bees, whereas dogs take weeks and are only right
about 71% of the time. So making honey, pollinating plants, and now
diagnosing diabetes— is there anything bees can’t do? But bees aren’t the only insects with smelling superpowers. Wasps can get in on the act, too. A tiny parasitic wasp called Microplitis croceipes lays its eggs in the bodies of living caterpillars. And it behaves differently when it smells
its host as opposed to its food, which means scientists can train a single
wasp to identify two different smells! On the downside, the wasps only live a few
weeks, and they only remember the scents they’ve
been trained on for a couple days. But on the upside, they’re cheap to raise, and are reportedly even easier to train than
bees. And according to researchers that have worked
with them, they can detect “almost anything”—they’ve
trained wasps on explosives, food toxins, and even the pheromones of bed bugs. In trials, the wasps were at least ten times
as sensitive to the test chemicals as the best electronic
sensors. The researchers even invented a device for harnessing the wasps’ super sniffing
ability. They call it the “Wasp Hound”, because
it’s kind of like having a trained bloodhound… except it’s a container
of wasps, that wiggle instead of howl. The wasps are held in a cartridge, which is
exposed to air samples. Based on their movements, the researchers
can tell whether the chemical they’ve been trained
on is present in the sample or not. Sniffer wasps could be used for jobs considered too dangerous for us or our loyal companions
to perform. But the startup hoping to market the wasps’
mad sniffing skillz hasn’t been too successful, so it’s unclear
if wasps will replace the hounds they’re named after
anytime soon. But even if some of these examples are still
conceptual, it’s pretty wild that all sorts of animals— from those with backbones and four legs, to
those with stingers and six legs— have these amazingly useful olfactory abilities. Whether it’s ridding the world of dangerous
explosives left over after wars, or finding gourmet fungus growing underground, these six animals follow their noses to do
some incredible things. If there’s a scent we need to track down that our human schnozzes can’t detect, there’s probably a critter out there that
can help us sniff it out. Thanks for watching this episode of SciShow. While our noses aren’t quite as keen as
the animals we just talked about, they’re not as bad at sniffing as you might
think. If you want to learn more about that, you can check out our episode about human smelling
abilities. [OUTRO ♪]
