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Uploaded:2020-12-06
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Humans aren’t the only ones who have to worry about epidemics: meet six other animals who take their own precautions to avoid getting sick!

Hosted by: Hank Green

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[♪ 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].