Name: 6つのマジで感動的な動物の移動 (6 Seriously Impressive Animal Migrations)
Uploaded: 2021-01-14T10:29:23.000Z
Duration: 9 min 1 s
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Every year, millions of animals undertake amazing journeys.

They migrate to avoid the cold, to give birth, or to find food,

and to do it, they can travel hundreds of kilometers over all kinds of terrain.

Now, you've probably already heard about things like geese heading south for the winter

or salmon swimming from oceans to rivers to lay eggs.

But these feats only represent a tiny fraction of how animals migrate.

There are some seriously impressive stories out there, and they come from all kinds of creatures;

some big and familiar, and others so small, you can barely see them.

Caribou are found in North America, Europe, Asia, and Greenland.

And if you're looking at this picture and thinking, “That's a reindeer!”, you're right!

They're the same thing, although the name changes

depending on where you live and whether the animal is domesticated.

Regardless of its name, though, some subspecies of caribou are serious migrators.

In fact, one of them, called the Grant's caribou, holds the world record for longest migration over land.

Each year, they take a journey that can cover more than 4,000 kilometers,

which is about the width of the entire United States.

And this adventure can span many types of terrain, taking them through ice fields or over mountains.

Like some animals, caribou do this partly to reach their calving grounds near the coast,

where they've given birth for generations.

But they also do it to find more high-quality vegetation

and even avoid pesky mosquitos and other biting insects.

In fact, when the insects are at their worst, these caribou actually travel the fastest,

Even though the caribou migrates the farthest over land,

its journey is nothing compared to the Arctic tern's.

and it holds the record for having the longest migration distance ever recorded.

When winter arrives in the Northern Hemisphere, the birds fly from the Arctic circle

in the northernmost part of the globe, towards the Antarctic circle in the southernmost part.

Now, that's already a long distance, about 15,000 kilometers,

but the birds can travel up to five times farther than that by taking a meandering route.

That long trek sounds exhausting, but it might be a smart decision for the birds.

One hypothesis suggests that traveling so far south helps the terns follow the bright summer sunlight.

That would allow them to see their aquatic prey more clearly,

and they could take advantage of the calmer summer breezes.

As for why they don't just fly straight to the Antarctic?

In a 2009 study published in the Proceedings of the National Academy of Sciences,

researchers attached lightweight geolocators to terns and tracked their migration routes.

They found that, along the way, the terns traveled over food-rich regions of the ocean,

flying along with the winds to help them keep up their energy.

In other words, the meandering route allows them to get in some good meals

Or fly themselves into the ocean. You get it.

It makes sense that birds and mammals would migrate in search of more favorable conditions.

But this next story takes place in oceans and lakes, with a much smaller creature: zooplankton.

These are tiny, aquatic organisms about as thick as a dime,

and they usually drift along with the currents since they're weak swimmers.

In fact, zooplankton could possibly hold two world records for migration:

the record for the smallest migrating animal, and the most numerous one.

Every day, up to billions of these animals participate in what's called diel vertical migration.

During the day, they migrate downwards into darker waters,

but at night, they go upwards, towards the surface.

Some evidence for this comes from studies of zooplankton in their natural habitats,

like a 2000 paper published in a German journal about freshwater biology.

In the study, scientists found that allowing artificial light to shine on a lake at night

significantly reduced the number of one type of zooplankton hanging out there.

And that makes sense, since that light mimicked the sunlight normally found during the day.

Other studies have found similar results with other types of zooplankton, too.

Some researchers suggest the animals do this to avoid predators that hunt with their sense of sight.

By sticking to the darker, deeper waters during the day,

there's a smaller chance they'll be spotted and eaten.

But they can't avoid their foes like this forever: After all, there's not a lot of food in those deep waters.

So at night, once the bright sunlight goes away, they might migrate to the surface to get their meals.

Next up, here's another world-record holder: the bar-headed goose.

If you live in the US, you're probably familiar with Canada geese,

which hang out in warmer climates during the winter.

But the bar-headed goose in Central Asia is arguably way cooler.

They're listed with Guinness World Records as the “highest migrant.”

To enter and exit their breeding grounds in Tibet,

these birds can fly more than 7,000 meters above the ground.

That's only about 2,000 meters lower than where commercial jets hang out!

They don't just do it for funsies, though.

They have to reach these altitudes because their migration path takes them over the Himalayas.

One of the tallest mountain ranges in the world!

At this point, it's not super clear why they take such an extreme route, though.

Scientists suggest it could give them an advantage over other animals,

or it could be because they've been flying this way for millions of years.

So maybe they had to adjust as the Himalayas got taller.

In any case, what scientists do know is that geese have evolved special adaptations

to deal with the low oxygen levels on their flights.

For example, they have a special type of protein in their blood

that lets them quickly absorb oxygen at high altitudes.

They also have more small blood vessels around their cells,

which improves how oxygen gets transported to their muscles.

In a 2019 paper, researchers even reported that the birds lower their metabolisms

and change the way they move their wings to conserve as much oxygen as possible.

So scientists will keep investigating why they migrate at such serious heights,

but one way or another, they're pretty great at it.

Now, Emperor penguins aren't exactly obscure.

They're featured in everything from primetime documentaries to children's movies,

because, well, have you seen them? They're great.

These birds live on the frigid, Antarctic side of the world, and you can often pick

them out by the yellow feathers around their necks.

Unlike some other birds, they don't migrate across continents and oceans,

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6つのマジで感動的な動物の移動 (6 Seriously Impressive Animal Migrations)

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