Lucy Cooke: Sloths! The strange life of the world's slowest mammal

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Hello.

Well, I'm here to talk to you about my animal muse: the sloth.

(Laughter) I've been documenting the strange lives of the world's slowest mammal for the last 10 years.

I still remember the first time I saw one.

I was fascinated by their freaky biology.

I mean, what's not to love about an animal that's born with a fixed grin on its face?

(Laughter) And the need to hug.

Audience: Awww. But sloths are massively misunderstood.

They've been saddled with a name that speaks of sin and damned for their languorous lifestyle, which people seem to think has no place amongst the fittest in the fast-paced race for survival.

Well, I'm here to tell you that we've got this animal all wrong -- and how understanding the truth about the sloth may help save us and this planet we both call home.

I traced sloth-based slander back to a Spanish conquistador called Valdés, who gave the first description of a sloth in his encyclopedia of the New World.

He said the sloth was "the stupidest animal that can be found in the world . . .

I have never seen such an ugly animal or one that is more useless." (Laughter) Tell us what you really think, Valdés.

(Laughter) I'd like to have a word about Valdés's drawing skills.

(Laughter) I mean, what is that?

(Laughter) I've never seen an illustration of a sloth that's more useless.

(Laughter) But I mean, on the plus side, he has given the sloth a remarkably humanlike face, and sloths do have remarkably humanlike faces.

This sloth I photographed in Costa Rica, I think looks a lot like Ringo Starr.

(Laughter) But then, sloths do bear an uncanny resemblance to the The Beatles.

(Laughter) Particularly pleased with Paul, actually, on there.

But like The Beatles, sloths are also extremely successful.

They come from an ancient line of mammals, and there were once dozens of species including the giant ground sloth, which was the size of a small elephant and one of the only animals big enough to eat avocado pits whole and disperse them.

So . . .

(Laughter) Some of you have worked it out already.

(Laughter) That means that without sloths, there might be no avocado on toast today, leaving hipsters everywhere totally bereft at breakfast.

(Laughter) (Applause) Today, there are six surviving species, and they fall into two groups.

You've got your Bradypus three-toed sloths, they're the ones with the Beatles haircuts and the Mona Lisa smiles.

Then, there are the two-toed sloths.

They look a little bit more like a cross between a Wookiee and a pig.

They live in the jungles of Central and South America, and they're extremely prolific.

There was a survey that was done in the 1970s in a Panamanian tropical forest that found that sloths were the most numerically abundant large animal.

They took up one quarter of the mammalian biomass.

Now, that's an awful lot of sloths and suggests they're doing something very right indeed.

So what if, rather than deriding the sloth for being different, we tried to learn from it instead?

We humans are obsessed with speed.

Busyness is a badge of honor, and convenience trumps quality in our quest for quick.

Our addiction to the express life is choking us and the planet.

We idolize animals like the cheetah, the "Ferrari of the animal kingdom," capable of doing naught to 60 in three seconds flat.

Well, so what?

(Laughter) (Applause) So what?

The sloth, on the other hand, can reach a leisurely 17 feet a minute with the wind behind it.

(Laughter) But being fast is costly.

The cheetah is speedy, but at the expense of strength.

They can't risk getting in a fight, so they lose one in nine kills to tougher predators like hyenas.

No wonder they're laughing.

(Laughter) The sloth, on the other hand, has taken a more stealthy approach to dinner.

They survive by capturing and consuming static leaves.

(Laughter) But you see, leaves don't want to be eaten any more than antelope do, so they're loaded full of toxins and very hard to digest.

So in order to consume them, the sloth has also had to become an athlete -- a digesting athlete.

(Laughter) The sloth's secret weapon is a four-chambered stomach and plenty of time.

They have the slowest digestion rate of any mammal.

And it can take up to a month to process a single leaf, which gives their liver plenty of time to process those toxins.

So, sloths aren't lazy.

No, they're busy.

Digesting.

(Laughter) Yeah, really busy.

(Laughter) Hard at work, that sloth, very hard at work.

And of course, leaves have little calorific value, so sloths have evolved to spend as little energy as possible.

They do about 10 percent of the work of a similar-sized mammal and survive on as little as 100 calories a day, thanks to some ingenious adaptations.

The Bradypus, three-toed sloths, they've got more neck bones than any other mammal, even a giraffe.

Which means they can turn their head through 270 degrees and graze all around them, without having to actually bother with the effort of moving their body.

(Laughter) It also means that they are surprisingly good swimmers.

Sloths can bob along in water three times faster than they can move on land, kept afloat by . . .

trapped wind.

(Laughter) So -- (Laughter) sloths are the only mammal that we know of that don't do flatulence.

When they need to expel gas, it's actually reabsorbed into their bloodstream and expelled orally as a sort of mouth fart.

(Laughter) Turning their lives upside down saves further energy.

They have about half the skeletal muscle of a terrestrial mammal.

They don't really have so many of the extensor muscles that are the weight-bearing muscles; instead, they rely on retractor muscles to pull themselves along.

They have long, hooked claws and a high fatigue resistance, so they can literally hook on and hang like a happy, hairy hammock for hours on end.

And sloths can do almost anything in this inverted position.

They sleep, eat and even give birth.

Their throat and blood vessels are uniquely adapted to pump blood and to swallow food against the force of gravity.

They have sticky bits on their ribs that prevent their enormous stomach from crushing their lungs.

And their fur grows the opposite direction, so they can drip dry after a tropical drenching.

The only problem is, if you turn a sloth the other way up, gravity removes its dignity.

Audience: Awww. They can't hold themselves upright.

And so they drag their bodies along as if mountaineering on a flat surface.

And I think this is why the early explorers like Valdés thought so poorly of them, because they were observing sloths the wrong way up and out of context.

I've spent many happy hours mesmerized by moving sloths.

Their lack of muscle hasn't impeded their strength or agility.

Nature's zen masters of mellow move like "Swan Lake" in slow mo -- (Laughter) with the core control of a tai chi master.

This one has fallen asleep mid-move, which is not uncommon.

(Laughter) But you're probably wondering: How does a dangling bag of digesting leaves avoid being eaten?

Good question.

Well, this is one of the sloth's main predators.

It's the harpy eagle.

It can fly at speeds of up to 50 miles per hour, has talons the size of a grizzly bear's, razor-sharp eyesight, and that ring of feathers focuses sound so that it can hear the slightest leaf rustle.

The sloth, on the other hand, has poor hearing, bad eyesight, and running from danger is clearly not an option.

No, they survive by wearing an invisibility cloak worthy of Harry Potter.

Their fur has grooves that attract moisture and act as tiny hydroponic gardens for algae, and they also attract a host of invertebrates.

So they are their own slow-moving, miniature ecosystem.

They become one with the trees.

And we think that their movements are so slow, they slip under the radar of the monstrous harpy as it's flying about the canopy, scanning for action.

Sloths are stealth ninjas, and they rarely leave the safety of the canopy -- except to defecate, which they do about once a week at the base of a tree.

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) Don't believe me?

(Sound of sloth scream) 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) 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?

(Laughter) Unlike other mammals, sloths don't also waste time maintaining a constant warm body temperature.

Energy from the sun is free, so they bask in the sun like lizards and wear an unusually thick coat for the tropics to keep that heat in.

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.

And I founded the Sloth Appreciation Society to both promote and protect their slow, steady, sustainable lives.

I'm a pretty speedy character.

I'm sure you've guessed.

And the sloths have taught me a lot about slowing down.

And I think that the planet would benefit if we all took a slowly digested leaf out of their book.

How about we all embrace our inner sloth by slowing down, being more mindful, reducing wasteful convenience, being economical with our energy, recycling creatively and reconnecting with nature.

Otherwise, I fear, it will be us humans that turn out to be "the stupidest animals that can be found in the world."Thank you very much.

May the sloth be with you!

(Applause)