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Sometimes humans seem like the laziest travelers.
We’ve built machines to carry us over land, sea, and air so we can go
farther than our ancestors ever could in a lifetime, all without breaking a sweat.
But while we manage to travel great distances without using much of
our own personal energy, we’re not alone in the world of lazy travelers.
Some animals can make it across long distances without having to work
nearly as hard as other animals that make similar journeys.
How do they do it?
Well, here’s five modes of energy-efficient travel that animals use all the time:
If you’ve ever seen Finding Nemo,
you know that sea turtles ride the currents to travel across huge distances.
Loggerhead sea turtles will ride them for years, drifting across entire ocean basins.
First, hatchlings emerging from Florida beaches hitch a ride on
the Gulf Stream current, which brings warm water from Florida
up the east coast of North America and across the Atlantic.
Then, they travel down toward Africa and back across the Atlantic in a full circle,
where the current becomes the North Atlantic gyre.
After hatching, it only takes baby turtles a couple of days to swim to
the Gulf Stream, where they’ll drift for the first months or years of their lives.
But baby turtles aren’t the only ones along for the ride.
Adults are better swimmers than their babies and
technically could swim faster routes, but they still often follow the currents too.
Now, just because they can ride the currents doesn’t mean they have to.
Researchers have measured sea turtle movement
using mini satellite tags that are only 10cm long.
They also use tools called “drifters” in the water
near the turtles to survey where the current is moving.
And by combining this tag information of where the turtles are going,
with drifter information of where the current is moving,
they can tell when turtles follow the currents and when they forge their own paths.
It seems that they’ll follow the currents for a long time,
passively but not helplessly floating along.
And that’s a big distinction.
There are places where the currents branch into much less favorable waters,
like the Northern edge of the North Atlantic gyre.
If turtles take the north branch up to Great Britain,
it’s so cold up there that they could die.
Data from turtle tags and current drifters suggests that
turtles will follow the current passively in more favorable waters but can make
more active decisions about swimming away from those less favorable waters.
Turtles aren’t the only passengers that choose to ride the currents.
Eels, fish, barnacles, mussels, corals, and mangroves also have their babies,
eggs, or seeds drift along in the currents.
And plankton drift on currents for their whole lives.
So sea currents are a popular mode of transit for the lazy ocean traveler.
But if sea turtles had the adaptations that tardigrades have,
they’d be able to ride the currents for longer without having to stop for food.
Because tardigrades can go dormant and
pause the need for water entirely while they travel.
Tardigrades are tiny animals only around 250 to 500 microns long,
so little that they basically float on the wind as specks of dust.
So being able to go dormant is incredibly helpful for their preferred mode of transit,
because there’s no easy way to get off this ride and stop for a drink.
At any life stage, even as eggs, tardigrades can curl themselves up
in a dehydrated and dormant state called anhydrobiosis,
where they pause their metabolic processes.
Curling up reduces the surface area on their bodies that
interacts with the dry wind on their journey.
By becoming dehydrated in anhydrobiosis,
they also become lighter to travel farther.
They can travel across entire continents this way and live without water for years.
And being able to go dormant also means they don’t need to direct their path
because they can basically live in any environment that the wind takes them to.
And once they reach their final destination, whatever that turns out to be,
they can rehydrate and recover their biological functions.
If you’d like to see some of those biological functions in action, you can find
tardigrade videos on our partner channel Journey To the Microcosmos.
So it looks like you can travel far on the wind without moving much
if you’re really small…
or really big, because the heaviest
flying animals basically glide the whole time.
Andean condors only flap their wings 1% of the time they fly.
That puts them among the laziest travelers,
as the least flapping of any recorded free-ranging bird.
Most of the flapping they do is during takeoff.
So once they get going, it’s smooth soaring ahead,
and they really don’t need to move much.
They stay up in the air without using their own energy
by using the kinetic and potential energy from air currents.
So just like the turtles on the water currents,
birds don’t necessarily travel the fastest route.
Instead, they catch thermal updrafts.
This means that the little flapping they do is to
put themselves where the updrafts are.
And even then, they only flap for about 2 seconds per kilometer.
Smaller birds are light enough that flapping isn’t too costly.
But for large birds like the Andean condor,
flapping their wings requires 30 times more energy than hanging out on land.
By gliding, they can soar for more than 5 hours,
covering about 172 kilometers without that costly flapping.
They can flap their wings to redirect their course.
But it isn’t as efficient as gliding,
so that’s what they spend most of their air time doing.
When animals like the Andean condor have
such an efficient way of getting around, why waste your own energy?
Instead, some animals like juvenile crayfish and snails
cling for dear life to birds’ feathers.
These animals are too big to go dormant and fly on the wind themselves,
but they have the next best thing: ectozoochory.
That’s the term scientists use to describe animals or plants
that stick to other animals as their means of transport.
One 2012 study found that most snails attach to bird feathers,
but they’ll also attach to feet or bills before flight.
Then they detach when the bird starts walking.
Now, snails are bigger than tardigrades but still pretty little animals.
So the fact that young crayfish can also travel
using this method is even more impressive.
The big ones have even more success using birds as planes than the little ones!
Mudsnails also better survive exposure to air
when they’re bigger and when the air is less dry.
So there may be a few reasons that larger animals travel better using this method.
For starters, smaller snails lose their moisture faster than bigger snails.
But since some snails can withstand being completely dried out,
some researchers think that their shell size and shape might
help some species form a seal against the bird so they don’t fall off in flight.
This lets them travel from one body of water to another.
And they can do this because they can survive out of the water
for long periods of time if they can manage to stay moist.
Mudsnails were found in one 2012 experiment to withstand
complete drying out for 24 hours, with some making it as long as 43.
Ultimately, however they manage to hang on,
these animals have a pretty efficient trip.
In one experiment, most crayfish survived traveling at 70 kilometers per hour.
And they could go for kilometers at a time.
But if clinging for dear life isn’t your style, there’s another way to use birds
as your personal airplanes: endozoochory, or, as I like to call it,
taking the gut train to Pooptown.
On second thought, is being eaten alive and
pooped out in a new habitat really better?
Either way, lots of plants and animals travel through guts to reach new habitats.
That’s right, guts aren’t just for parasites anymore.
Some species use this method when they’re still seeds, eggs, or spores.
But grown animals can also travel by endozoochory.
For example, a 2012 study found that a certain kind of mudsnail
popped out of mallard ducks up to five hours after they were eaten
and were still fully functional!
Knowing how fast mallards fly, this means these snails could
travel up to 300 kilometers using this method.
Now it might not be worth it for most snails, who are pooped out early in flight
and might just end up going splat.
But for the lucky ones who make it across huge distances,
it may be a different story.
Researchers have suggested that this method
helps snails stay genetically diverse by keeping isolated populations connected.
And they’ve proposed that animals might have adapted to survive in
these extreme environments accidentally by adapting for wetlands.
Having a thick shell comes in handy not only to protect
against predation in wetlands, but also to shelter snails from being crushed
in a gizzard and from letting digestive enzymes break them down.
Another possible explanation for these snail’s survival is that birds might
not be devoting as much energy to digestion while flying.
So the snails might not be getting the bird’s best digestive efforts.
In the end, snails will hitch a ride on the outside or
the inside of another animal to find greener pastures.
Who would have thought that the little snail is one of the
best and most efficient travelers in the world?
But there’s one last traveler we have to mention: plants.
Because despite not having legs, plants have come to
live in every corner of the globe.
And in the book The Incredible Journey of Plants by Stefano Mancuso,
you can learn how!
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