Lucy Cooke: How Did Slowness Become The Sloth's Secret To Survival? It's easy to see why sloths have become icons of laziness. But zoologist Lucy Cooke says behind their leisurely pace is a marvelous evolutionary advantage that is the secret to their survival.
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Lucy Cooke: How Did Slowness Become The Sloth's Secret To Survival?

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Lucy Cooke: How Did Slowness Become The Sloth's Secret To Survival?

Lucy Cooke: How Did Slowness Become The Sloth's Secret To Survival?

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(SOUNDBITE OF MUSIC)

MANOUSH ZOMORODI, HOST:

It's the TED Radio Hour from NPR. I'm Manoush Zomorodi.

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ZOMORODI: And on the show today, we are surrendering to things that take time.

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ZOMORODI: And let's start with a moment or two appreciating the slowest mammal in the world.

LUCY COOKE: There is no other animal like them on the planet.

(SOUNDBITE OF SLOTH SQUEAK)

ZOMORODI: The sloth.

COOKE: There is no other animal that comes with a built-in philosophy.

(SOUNDBITE OF SLOTH SQUEAK)

ZOMORODI: This is Lucy Cooke.

COOKE: And I am a writer, broadcaster, conservationist, zoologist. I wear a lot of hats. But mostly, I'm known for being a huge advocate of sloths.

(SOUNDBITE OF SLOTH SQUEAK)

ZOMORODI: So, Lucy, do you remember the first time you saw a sloth in person?

COOKE: I do. I do. I was traveling around South America trying to raise awareness about endangered amphibians. And the one non-frog-based thing that I did was visit a sanctuary in Costa Rica, and I was not disappointed (laughter). I - it was love at first sight. I was just...

ZOMORODI: Wow.

COOKE: ...Mesmerized by their strangeness because they are - they really are slow. And that's quite stunning.

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COOKE: They are extraordinarily graceful. They really do move like a ballet dancer that's been slowed down. You know, it's like they have this incredible control.

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COOKE: And what's kind of amazing about that is they actually manage to move so gracefully with 50% less muscle mass than most upright mammals. So, you know, for the zoologists, you're just - your brain's just working overtime, going, how does that work and why, why, why, you know? (Laughter).

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ZOMORODI: That was back in 2010. And Lucy has, since then, been obsessed with sloths.

COOKE: This is a lifelong commitment I've made (laughter). You know, it would be churlish and inappropriate to have a fleeting fancy with the sloth, wouldn't it?

ZOMORODI: We live in an era of instant gratification, a culture that prizes efficiency over patience. But some things, to reach their full potential, they simply cannot be rushed. Optimizing or speeding them up is impossible. And given how the past year has warped our sense of time, perhaps we're ready to value a different tempo. And so today on the show, ideas and projects that take time - how a more deliberate pace can be productive if we revel in it or if we observe how another creature embraces it, like the sloths. Lucy Cooke says that living in slow motion is the ultimate evolutionary adaptation.

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COOKE: Sloths are completely perfect. They're as perfect as you or I, and they're perfectly adapted to their arboreal lifestyle. And they are rather unusual because they are the world's only inverted quadrupeds. So they are a four-legged animal that lives most of its life upside down.

And there are two different types of sloth. You have two-toed sloths, and they're the ones that look basically like a cross between a Wookiee and a pig, actually. They've got this sort of really kind of boopable (ph), kind of pig-like nose and sort of beige-brown fur. And then you have your three-toed sloths, and they're the ones that have got, like, a sort of a band across their eyes, and they've got kind of medieval haircuts and Mona Lisa smiles. And they're quite different. They're actually as genetically different as cats and dogs.

ZOMORODI: Really?

COOKE: Yeah. Yeah. 'Cause the sloths were once a huge group. There were, like, sort of over 50 species, including giant ground sloths and all sorts. So the ones that are left, they're from that group, but they're all the small ones that live in trees, basically - are the ones that survived.

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ZOMORODI: And Lucy says the secret to their survival is their metabolism.

COOKE: Fundamentally, they're vegetarians, and they live on leaves. But, you know, leaves don't want to be eaten any more than antelope do, you know, so they're loaded full of toxins. And so in order to digest those leaves, sloths have a very slow digestion rate - takes them up to a month to digest a single leaf.

ZOMORODI: Wow.

COOKE: Yeah.

ZOMORODI: Lucy Cooke continues from the TED stage.

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COOKE: Sloths have a freakishly low metabolism. And we think that this might be one of the reasons that they can sometimes recover from injuries that would kill most animals. This sloth recovered from a double amputation, and I've known sloths that have managed to survive even power line electrocutions. And we now think that a low metabolism may well be key to surviving extinction. Researchers at Kansas University who were studying mollusks found that a high metabolism predicted which species of mollusk had gone extinct. Sloths have been around on this planet in one shape or another for over 40 million years. The secret to their success is their slothful nature. They are energy-saving icons.

This is a creature that everything about it is shaped around burning very little energy - slow digestion, slow metabolism - and so they have all these adaptations to living on a very low-energy diet, which is, you know, having a very slow metabolism and living upside down, for example. That requires less energy and less muscle just to dangle from a tree.

ZOMORODI: Go with gravity.

COOKE: Yeah, exactly. Go with gravity 100%. If you got the option, hang out from a tree like a happy, hairy hammock. It ain't - it's going to save you a lot of energy if you can. If you can, do it.

ZOMORODI: So what is a sloth's kind of ideal day?

COOKE: They basically spend their entire day waking, snacking, snoozing, repeat.

ZOMORODI: Sounds so good.

COOKE: Yeah. And then once a week, a major event happens, and that's the need to take a poop.

ZOMORODI: Nice.

COOKE: (Laughter) And then they'll climb a great - this laborious climb down from a tree in order to do their business at the bottom of a tree, which is a conundrum that has mystified scientists for many, many years because why would you do that? Because when you come to the ground, you're completely vulnerable and, you know, could get attacked by jaguars and ocelots or whatever. We think that they do it in order to send love messages to...

ZOMORODI: Oh.

COOKE: ...Other sloths. I know. It doesn't sound terribly romantic to us.

ZOMORODI: No.

COOKE: But yes, you know, romance is a latrine-based sport, if you're a sloth.

ZOMORODI: (Laughter).

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COOKE: Now, this risky and energetic behavior has long been a mystery, and there are lots of theories as to why they do it. But I think they're leaving surreptitious scented messages for potential mates because, you see - sloths are generally silent, solitary creatures, except for when the female is in heat. She will climb to the top of a tree and scream for sex in D-sharp.

(LAUGHTER)

COOKE: Don't believe me?

(SOUNDBITE OF SLOTH SCREAM)

COOKE: D-sharp. This and only this note will get the male's attention. It mimics the sound of the kiskadee flycatcher. So the female remains covert, even when yodeling for sex at the top of her lungs. Her clandestine booty calls will carry for miles across the canopy, and males will beat a slow path towards her.

(LAUGHTER)

COOKE: I think scented messages in her dung will help send Romeo up the right tree so that he doesn't waste precious energy scaling the wrong one. Sex, by the way, is the only thing that sloths do swiftly. I've seen them do it in the wild, and it's over and done with in a matter of seconds. But then why waste precious energy on it, particularly after that journey?

ZOMORODI: (Laughter) So how has this world's slowest mammal been able to survive for millions of years? Because it's not like they can outrun predators.

COOKE: Well, do you know what? That was exactly the same question that the early naturalists were completely, like, befuddled by this creature because they're like, how does it escape from being eaten? Like, how does that happen, you know? But actually, it just - it doesn't escape by running away. It escapes by being cryptic, you see.

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COOKE: So their fur actually has grooves in it that traps moisture and allows algae to grow so that they often have a greenish hue, the wild sloths. So they totally blend in with the trees. They look and smell just like a tree. So they - and its movements are so slow that we think that they pass under the radar of the harpy eagle, which is their main predator, as they fly around the treetops scanning for motion. You know, they don't crash around and make a load of noise like monkeys do. They're really hard to spot because they're silent and solitary and totally camouflaged. So that's how they've done it, really. It's just a different way, you know, which I find very pleasing.

ZOMORODI: When I first think of the word sloth, it's related to idle and laziness and being a bit of a heathen - right? like, a sinner, as it were. But the sloth has had sort of a makeover in the last few years. Why has it changed from being the emblem of all that is idle to this lovable creature who kind of symbolizes a simpler, kinder, slower way of life?

COOKE: Well, I think that when I first stumbled across them 10 years ago, nobody had really heard of them. And then now they are everywhere, you know, for sure. And I think to a certain extent, I'd like to think that we are all becoming aware that our lives as humans are unsustainable.

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COOKE: And maybe we're fed up with moving too fast and being in the rat race and running in a hamster wheel every single day to what end, you know? And maybe this having been something that was considered to be a sin, you know, is now an aspirational quality, the idea that you could be slow, and that would be OK. So yeah, I mean, you know, it's cheesy, but I think taking a leaf out of the - a slowly digested leaf out of the sloth's book is - isn't a bad thing to do.

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ZOMORODI: That's Lucy Cooke. She's a zoologist, author and founder of the Sloth Appreciation Society. You can hear her full talk at ted.com. On the show today, it takes time - how some things you just can't rush. I'm Manoush Zomorodi, and you're listening to the TED Radio Hour from NPR. Stay with us.

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