[♪ INTRO] We are covered in germs all the time—because
the world is just full of viruses, and bacteria, parasites, and fungi. Scientists estimate that we come into
contact with about 60,000 germs per day. Luckily, only a small fraction
of them actually make us sick, and we’ve developed lots of habits
that help us combat these germs— like washing our hands, avoiding sick
people, and, these days, wearing a mask. But we’re not the only animals that
have to worry about harmful germs, things called pathogens. All animals that live communally
have to ward them off— or they can suffer outbreaks
and epidemics just like we do. And while other animals don’t
have hand sanitizer or masks, many of them do have extraordinary
ways of preventing the spread of germs. So we’re going to look at 6
ways animals prevent outbreaks and we will award a prize to the animal we think deserves special recognition in each category. One good way to prevent an outbreak
is to just avoid coming into contact with the organisms and other objects
that carry disease in the first place, things known as vectors. Like, for us, mosquitos
are an important vector for dangerous diseases like malaria and Zika— which is why we sometimes use pesticides
to kill mosquitoes and their eggs. But different animals have other, brilliant ways of reducing the number
of vectors they cross paths with, which helps them avoid exposure to pathogens. And in this category, the prize goes to bluebirds. Bluebirds are native to North
America, and they nest inside tree holes made by woodpeckers. They fill them with grasses and other soft stuff and then use this nest cavity over
and over again, for multiple broods. Which doesn’t sound so sanitary. Old eggshells and goo, leaves, dead
hatchlings, or rotting unhatched eggs are magnets for ticks, mites, or
other potential disease vectors. But bluebirds are fastidious. They remove everything that could
attract vectors and pathogens by tossing it right out of the nest. Their nests are spotless. Nature has even given them a natural
solution for dealing with baby bird poo. See, when baby bluebirds first hatch, their eyes are still closed and they
can’t walk, so they’re totally helpless. Meaning, unlike some other species, they
can’t poop over the side of the nest. They have to poop right in it. And that sounds like it would be at
odds with bluebirds’ tidy habits. But their poo is enclosed in a
whitish membrane called a fecal sac to keep it from making a mess. It’s basically a bird diaper. Except the parents don’t even have to change it! All they do is grab it with their
beaks and toss it out of the nest. This way, the nest stays sanitary
till the hatchlings fledge, and it can be used for one brood after another. Unfortunately, avoiding vectors
and pathogens can be hard— which is why sometimes it’s more
practical to just create a barrier. We humans use things like gloves and
masks to keep pathogens from reaching us, but we’re not the only
animals to use this strategy. In fact, the prize for creating
a barrier goes to honeybees. Honeybees aren’t just ordinary
social animals like we are. They live so closely together in a
cooperative lifestyle that they’re considered superorganisms, because the whole
hive acts like one big organism. This extremely dense living arrangement
is risky—because any germ that makes it inside the hive could
easily spread and cause an outbreak. But those close quarters are also an opportunity: they give honeybees a chance to
achieve what’s called social immunity, which is any shared way of keeping
the whole group safe from pathogens. And honeybees do this by using resins. You might know of resins as the
goo that comes out of fir trees, but a resin is just a broad term
for a mixture of plant compounds that happen to have antifungal,
antibacterial, and antiviral properties. Many flowering plants make them too. And honeybees take advantage! First, a forager bee will fly out and load
up the pollen sacs on her legs with resins, which she brings back to the hive. There, other bees remove the resins
from her pollen sacs by biting them off— which can sometimes take hours. Then they combine the resins
with wax and bee saliva to make a sticky mixture called propolis. These nestmates stick that propolis on
the hive walls and smooth it with their mandibles to coat the entire inside
of the hive, kind of like spackling. And since the propolis has
antimicrobial properties, it prevents certain pathogens
from making it into the hive. But a barrier isn’t always an option. Sometimes pathogens get right up in your business, and you just need to get rid of them. Humans get rid of pathogens by sanitizing. For instance, we wash with soap and
wipe down surfaces with chemicals that kill viruses, and bacteria, and fungi. And while other animals can’t exactly do
that, some do have other ways of sanitizing. The prize in this category goes to rats. Because for an animal that
loves garbage and subways, rats actually keep their coats surprisingly clean. And they do that by grooming. Grooming is generally a way to clean
the surface of an animal’s body by removing anything that doesn’t
belong, like dirt, old hair, or parasites that may carry
bacteria or other pathogens. And physically removing that stuff can
help a lot with cleanliness. But when rats groom, they’re also using chemicals
in their saliva to kill pathogens. Rat saliva has natural components
like the enzyme lactoperoxidase, as well as natural hydrogen peroxide. Those chemicals react with each other
to make an antibacterial compound that helps prevent the growth of bacteria. And research has found that male rats
spend up to a third of their waking hours grooming to prevent the spread of germs. They even go so far as to
sanitize their penises after sex, to kill pathogens that could cause
sexually transmitted diseases. So, no matter what you think of their lifestyle, you have to hand it to them: Rats are excellent at keeping themselves clean. One of the most basic practices we
humans use for avoiding sickness is just avoiding people who might be sick. Like, you maybe have crossed the
street to avoid people during… a pandemic for example, or you’ve rescheduled your lunch with
a friend whose partner has a cough. And you wouldn’t be alone: Other animals
shun their sick too, and oddly enough, the prize-winner here would have to be… lobsters. Now you might not think of
lobsters as social enough to be in the running for an epidemic
prevention prize. But some are! For example, Caribbean spiny
lobsters congregate in communal, underwater shelters in rocks or corals, and they use chemical signals
called pheromones to socialize. On a good day, a young spiny lobster
might give off certain pheromones to invite others to hang out in its den. And similarly, on a not-so-good day, when
a spiny lobster is infected with a virus, chemical clues in its urine can alert
other lobsters to the fact that it is sick. When that happens, the healthy
lobsters will shun the sick one by moving out of their dens and finding new ones. In fact, they’re so bent on avoiding infection that they’ll find shelter
wherever they can get it— even in more dangerous places, like
crevices that smell of predatory octopuses! This type of social avoidance
is called behavioral immunity, and it can be extremely effective at
preventing the spread of a pathogen. That seems to be especially true for lobsters, because thanks to their
sensitivity to chemical clues, they start shunning a fellow
lobster before it even acts sick— at least as far as we can tell. And it pays off! As a result of
these sorts of extreme measures, spiny lobster populations are extremely
resilient to dangerous infections. But some creatures don’t just wait to be shunned— they’ll go ahead and separate themselves
from the rest of the population. We humans do this a lot, especially since
the beginning of the COVID-19 pandemic: If you’re sick, you stay home. But you don’t have to be a sophisticated
social creature with a good conscience to self-isolate. In fact, the prize-winning
species in this category is ants. Ants actually use a lot of tactics
to prevent the spread of the disease, such as repelling pathogens with resin,
grooming each other to remove parasites, and cleaning dead ants out of the colony. But on top of all that, ants
also appear to self-isolate. In two different studies in 2007 and 2011, scientists infected ants with pathogenic
fungi and tracked their behavior afterward. And they noticed some important changes. Normally, worker ants help care for the baby ants by feeding larva and keeping eggs clean. But ants that had been infected with
fungi mostly stayed away from the larva, and non-infected ants actually
stepped up to take care of the young. The infected ants also got less sociable. They spent more time outside of the nest and acted aggressive towards their nestmates. While it’s tough to know how
ants make their decisions, researchers believe it was a
reaction to being infected, since the ants became antisocial right
after the fungi entered their bodies. And that suggests that their social
withdrawal is meant to protect others. Finally, an important step we humans often take if a member of our group gets
sick is we give them medicine. Medicine is often just
chemicals that kill pathogens— like antibiotics, antifungals, or antivirals. And, in a way, other primates
actually use medicine too. So, our last prize—for the animal
with the best use of natural medicine— goes to hamadryas baboons. Hamadryas baboons live in East Africa,
in areas where they can find fresh water. Unfortunately, that’s also where certain
flatworms live, known as schistosomes. Schistosomes burrow into the skin
and travel through the bloodstream, which can cause bleeding, diarrhea,
and eventually organ damage. They’re dangerous for both humans and
baboons if they get into the body. But hamadryas baboons protect themselves by munching on the berries
of the desert date tree. This tree has a bunch of
chemicals called flavonoids, which have antimicrobial properties that
are used in lots of modern medicines to treat conditions ranging
from cancer to dementia. And one of the things those
chemicals can knock out are infections caused by schistosomes. People in East Africa have used
natural flavonoids for a long time to cure schistosome infections,
as well as other illnesses. And while you might think the baboons just
happen to like eating the plant as food, scientists think they actually
know what they are doing. Because unlike when they eat the food for
calories, they don’t chew up the leaves. Instead, they just suck the leaves
to extract the medicinal juices. They seem to have figured out that this
can help protect them from infection. All of these animals show us that
fighting diseases from pathogens is not something unique to humans. Across animal societies, organisms go
to great lengths to prevent epidemics, and in many ways, they battle
sicknesses a lot like we do. Thanks for watching this episode of SciShow! And if you liked it, you might be
interested in our video about five times people gave animals diseases. You
can watch that one right after this. [♪ OUTRO]
