Hi, this is Kate from MinuteEarth.
Among animals, some species seem to have it all, and others...don’t.
Today, we’re sharing four tales of winners and losers in the animal kingdom.
Let’s get right to it with a tale about, well, tails.
Many of the monkeys scampering around the forests of Central and South America have
something special on their butts: an extra hand.
Well, not exactly; it’s a prehensile tail, a grasping appendage that helps the animals
navigate the tall and treacherous canopy in search of fruits and leaves.
In fact, these tails are so handy that monkeys in the Americas have evolved them two separate
times, and they’ve evolved dozens of times in other mammals, reptiles, amphibians, and
fish.
But there’s a big group of monkeys in which these handy appendages don’t exist.
In Africa and Asia, monkeys’ tails are just...tails.
Which is weird, because those monkeys also spend all day monkeying around in the canopy
and could presumably use an extra hand for foraging too.
So where are their special tails?
Our best guess is that the difference in tails is due to a difference in the forests where
those tails appear.
The forests in Central and South America are chock full of vines that monkeys use like
tightropes to traverse between trees, so having an extra grip is helpful for balance - and
helpful in case of emergency.
But on the other side of the world - at least in Asia, where we have the most data - forests
have fewer vines, and monkeys there often go to the ground to travel between trees.
Prehensile tails take a lot of extra energy to operate, so it’s possible that they just
aren’t useful enough to those monkeys to be worth having.
On the other hand, there might be no good reason at all for the difference.
By pure chance, monkeys might have evolved in one way on one side of the world, and in
another way on the other.
But, considering prehensile tails evolved twice in monkeys in the Americas, the vine
theory of appendage evolution is the easier explanation to latch on to.
Plus, it’s a pretty gripping tale
Ok, I would definitely have a prehensile tail if I could.
Or I’d be a big, scary apex predator….those are definitely winners, right?
Well, not necessarily.
Allow us to explain - in song.
The food webs of the world all used to have so-called apex predators – like lions, tigers,
and bears – at the very top.
But humans have posed a major threat to apex predators by breaking up their habitats and
hunting many of them to near extinction.
It was good to be king We were trophic elite
Prey ate the plants And we ate their meat
Then this little ape called “Man” Wanted to compete
And as the humans spread And invaded globally
They broke up our habitats And killed us all - rather fast
They were shooting us for sport Or for eating sheep
Lions, lynx, and sea eagles Alphas worldwide
Met precipitous decline Leopards, wolves, and hammer-heads,
Were persecuted Leaving disarray behind
Not to throw shade, but this Trophic downgrade
Will simply open up space for some lesser-grade So-called hunters
These so-called hunters are the mesopredators.
They’re replacing apex predators all over the world, and they do things differently.
Skunk… raccoon... mahi mahi… mongoose Catshark… dogfish… jackal… large squid
Food chain food chain food chain food chain food chain (woof)
Apex out - we the new thing (youth) And we don’t need a huge range (ooo)
As you get killed by the humans (ooof) Mesopredators gonna move in (truth)
Say goodbye to our old foes.
(ooo) Yeah what a relief! (phew)
No competition or hunting.
(coo) So Mesopredators are released! (ooo)
When farmers hunt down lions (shoot) Just to protect livestock (moo)
Nobody left to eat baboons (baboon) Who start eating all the crops! (true)
Sharks getting killed for their fins?
(stew) Boomtime for the rays and skates (ooo)
But they eat all the bivalves (food) Humans left with an empty plate (poof)
Fence out all the dingoes?
(shoo) Foxes rise in a blink (ooh)
And as the fox keeps hunting (ooh) Little mammals go extinct (potoroo)
But we’re not just thriving (coup) Due to the apex crash (boom)
Living near humans is rich (ooh) We’re sitting here eating up trash (and
rats!)
Food chain food chain food chain food chain food chain (woof)
Trophic cascades happen quick with apex gone and we’re turned loose.
We can thrive by human side, rise up the food chain ‘til we rule
The rule of mesopredators has wreaked havoc on many ecosystems, so in some places, humans
have helped reintroduce some old-school apex predators to keep the mesopredators in check.
In Yellowstone, which had been our home We used to eat up coyotes
But as we were killed, coyotes were thrilled It was a mouse and rabbit feast!
But that hurt the hawks, badgers, and fox.
Who had relied on them for meat.
But since we’ve returned, they’re starting to learn
That we can help other specieeees
Reintroducing wolves to Yellowstone helped restore the whole ecosystem.
But most people don’t want a wolf in their backyard – or a lion, tiger or bear – so
mesopredators will continue to rise to the top of the charts.
Food chain food chain food chain food chain food chain (woof)
Oh, man, a lot of you HATED that video when we put it out.
But even the haters have to admit... food chain food chain food chain food chain food
chain food chain is a winner of a song.
Anyway, the whole mesopredator thing is far from the only instance in which we humans
have turned some animals into winners and others into losers.
About a million years ago, some intrepid black bears and ferrets crossed the Bering land
bridge into North America.
Over thousands of generations, the ferrets and bears on different continents became different
species, but they still look and act a lot alike.
But the American bear and the Asian ferret are thriving, while the Asian bear and American
ferret are at risk of extinction.
Both sets of cousins owe their uneven luck to another intrepid species – a hairless
ape that began its rapid spread some 60,000 years ago, eventually crossing the same land
bridge into North America.
As its numbers grew, many other species' numbers and habitats shrank.
And everywhere it went, the human's big brain helped it develop the tools for success, but
it also gave it all sorts of ideas about the new animals it came across.
In Asia, people wrongly came to think that bear bile helped cure common ailments and
started killing and imprisoning bears for their gallbladders, which they do to this
day.
Combined with habitat destruction, this has decimated the Asiatic black bear population,
which has been cut in half in the last three decades alone.
Meanwhile in America, many fewer people hunted bears after they decided that they were pretty
cute.
More recently, North Americans have also moved much more rapidly from farms to urban areas;
the new-growth forests that are popping up in their absence happen to be the perfect
habitat for bears.
In fact, it’s so good that there are now about twice as many black bears roaming the
woods of North America as there were when European colonists first arrived 500 years
ago.
The North American ferrets haven't been so lucky.
Their primary food source, the prairie dog, was happy eating grass and breeding like crazy
until ranchers – worried that there wouldn't be any nosh left for their cows – started
killing off the liddle fuzzy wuzzies.
With nothing to eat, the ferrets went extinct in the wild.
Asian ferrets, on the other hand, have a favorite food source that humans haven’t killed off,
and they’re still thriving in most parts of Europe and Asia.
So, it’s not like the Asian ferret and the American bear are better species than their
close cousins - whatever that even means.
They just got lucky that humans in their part of the world didn’t decide to ferret out
their favorite food or bear down on their bile.
So, what can we do to ensure that ecosystems don’t bear the brunt of our actions?
And are our puns starting to become un-bear-able?
We take a look at answering the first question in this next video...and as for the puns,
they don’t bug me.
Earth’s ecosystems have always been changing, with species mixing and mingling thanks to
migrations, freak events, and slow creeping expansions.
But since we humans arrived on the scene, we’ve put things into fast­-forward, moving
plants, animals, and other organisms around the globe – whether intentionally or not.
Once in a while, one of these transplants might have an evolutionary quirk – like
deadly poison, a lack of predators, or a voracious appetite – that unexpectedly helps it dominate
its new territory.
Earthworms, for example, were introduced into North America by European settlers and have
been inching across the continent ever since, tilling soil and improving crop yields as
they go.
But if a newcomer starts to harm us or a part of the environment we care about, we’ll
call it an “invasive species.”
Technically ­speaking, humans aren’t "invasive," because we don't usually consider ourselves
an ecological threat to... ourselves.
But other species certainly are.
One way they get our attention is by costing us money.
A lot of money.
The US spends billions of dollars fighting invasive weeds like the pretty but pesky yellow
rocket flower that chokes fields and creeps onto golf courses and lawns.Other invaders
wreak so much havoc on fragile ecosystems that we can’t help but notice even if billions
aren’t at stake.
For example, the yellow crazy ant, a likely native of Southeast Asia­ has been nom-nom-nomming
many beloved and endangered Australian creatures since its arrival several decades ago.
These little ants feast on nearly anything and everything in their path: ­insects, amphibians,
birds, small mammals, even the famous red crabs on Australia’s Christmas Island, which
used to keep the island’s undergrowth in check; without them, the ecosystem has veered
into chaos.
But noticing invasive species is easy.
­Dealing with them is the real bugger.
When we brought rabbits to New Zealand for food and fur,they escaped and bred like...well...rabbits,
overrunning the country.
So we introduced ferrets to control the rabbits; but they too spread like wildfire, generally
ignoring the rabbits while gobbling up rare species like the now nearly ­extinct kakapo.
New Zealand is still overrun by both furry fiends, and this is just one of many well­-meaning
attempts at biological control that have ended in disaster.
The best way to fight an invasion is to first arm ourselves with knowledge: Instead of trying
to kill Australia’s yellow crazy ants by just spraying insecticide everywhere, we’ve
learned that the best approach is a year­-long multi­step assault that specifically targets
ant-riddled areas at the times when the egg-laying queens are mature and susceptible to our treatments.
Then we spread two kinds of bait for the workers to bring back to the nest: one kills, and
the other to sterilize the queens.
Neither chemical is perfect, but executed together, they can knock out a whopping 99
percent of the population.
But with many invasives, even 99% isn’t enough, because it doesn’t remove whatever
advantage gave the invaders an edge in the first place.
So unless we honest­-to-­goodness get rid of every reproductively active individual,
eventually they’ll return as vigorously as before, keeping us constantly on our toes.
We really just need to stop moving potential troublemakers around in the first place, leaving
bunnies where they belong and making sure ants and earthworms don’t stow away on ships,
cars or excavators.
But in a modern, globalized world, this is easier said than done.
For those species that we do accidentally (or intentionally) let loose only to see them
spread wildly out of control, our best hope is to learn as much as we can about their
habits and their biology ­ only then do we have a chance of keeping their harmful “ant”­ics
at bay.
So understanding the traits of some of these winners can ultimately help us win against
them….knowledge really *is* power.
And if you’re looking for even more of that all-powerful knowledge - say, about why organisms
do or don’t succeed - you should check out Brilliant, who sponsored this video.
I took Brilliant’s computational biology course, which has an awesome section where
you can follow a population of self-replicating robots from Chile to Mars and see how they
adapt.
These kinds of thought experiments and quizzes break up big, intimidating concepts like computational
biology into interesting, bite-sized chunks.
If you want in on this, go to brilliant.org/MinuteEarth and sign up for free.
And as a bonus for MinuteEarth viewers, the first 200 people that go to that link will
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Click on the link in the description and try Brilliant now.