Why Are Sloths So Slow?

https://slothconservation.org/sloths-move-slow/

by rzk • 2 years ago

204 101 2 years ago

ajb• 2 years ago

See also the delightful Sloth song of Flanders and Swann: https://m.youtube.com/watch?v=blDNO5qznjM

roughly• 2 years ago

Today I Learned from a link on that page that sloths camouflage themselves by growing algae on their fur and moving very slowly: https://slothconservation.org/with-a-little-help-from-my-fri...

nsguy• 2 years ago

IIRC they also come down from their tree to poop once per week.

TheRoque2• 2 years ago

And the poop can be up to 3/4 of their total weight

dumpHero2• 2 years ago

Why do they come down to poop?

kulahan• 2 years ago

For a less-fun fact: tons and tons of bugs live in their fur. Sometimes literally thousands of moths, beetles, etc. are living in their fur. Some bug species are only found on sloths.

klondike_klive• 2 years ago

It occurred to me for the first time the other day that the word "sloth" is to "slow" what "warmth" is to "warm".

mc32• 2 years ago

And some people do pronounce the word “slow-th” though it’s atypical.

vrc• 2 years ago

Many would bristle at you referring to Sir David Attenborough as atypical!

NovemberWhiskey2• 2 years ago

It’s how it’s pronounced in British English.

sudobash1• 2 years ago

I have always heard this pronunciation in American English when referring to the vice.

endofreach• 2 years ago

Well, it would be "slowth"...

Which makes me think: i am surprised that is not an excessively used term in the startup / brotrepreneur world...

walrus01• 2 years ago

"slowth" is how David Attenborough pronounces it, and if anyone could be considered an authoritative English language expert on the common (non-latin) names of mammals, he would be it...

schoen• 2 years ago

Apparently it was historically spelled in a way that makes the slow + -th connection more apparent!

https://en.wiktionary.org/wiki/sloth#Etymology

jagged-chisel• 2 years ago

One of the seven deadly sins

moffkalast• 2 years ago

Rule number one: Cardio.

ks20482• 2 years ago

According to wiktionary, these are the examples of -th "Used to form nouns of quality from adjectives. (no longer productive except jocular coinages)":

breadth, chillth, coolth, dampth, dearth, depth, filth, health, height/heighth, illth, length, roomth, ruth, strength, troth, truth, sloth/slowth, warmth, wealth, width, wrath, wrength, youth/youngth

eastbound• 2 years ago

When you want to make them adjectives again… add a “y”: wealthy, truthy, healthy…

(As a foreigner I’m curious what the original adjective was for filth, length, ruth, wealthy, wrath).

Mordisquitos• 2 years ago

"Used to form nouns of quality from adjectives. (no longer productive except jocular coinages)"

But enough jocularth can eventually result in -th becoming productive again!

SamBam2• 2 years ago

heighth

I've heard this said, and seen this in plenty of codebases. `let width = 10, heighth = 10`

Its intuitive match to "width" makes me wonder why it ever became "incorrect."

sethammons• 2 years ago

so _that_ is why some pronounce it "slow-th" vs "sloth" (that rhymes with cloth)

yndoendo• 2 years ago

"The Unexpected Truth about Animals" by Lucy Cooke talks about this and goes into more detail. Enjoyed the other animals too. It has a good example of how humans will still ignore reality in the animal kingdom when it comes to religious beliefs.

[0] https://www.goodreads.com/book/show/34211802-the-unexpected-...

agumonkey• 2 years ago

There should be social activities that revolves around spending a lot of time in nature close to animals.

soneca• 2 years ago

”Research has shown that all sloths have a rare genetic condition called ‘rod monochromacy’”

Weird phrasing. All of them having something that is rare means it is not rare at all, right? And if all of them have it, it is not a “condition”, it is their genes, how they are.

Retric• 2 years ago

It’s rare among mammals in general even if it’s universal for sloths.

Most people think of evolution as a string of improvements, however you can get negative traits in a population from a large enough genetic bottleneck or spread by being next to a very useful mutation. So it’s not necessarily an advantage for them, it could have just been bad luck.

Alternatively, there could have been some selective pressure for it as a means of improving night vision or something, we just don’t know.

whyslothslow• 2 years ago

Wait. So why are sloths so slow?

I read this whole article and it’s still not clear to me _why_ they’re slow.

I’m genuinely curious! It seems like this article just lists a bunch of facts about sloths. But doesn’t say why being nearly blind or having a slow metabolism gives any evolutionary advantages.

Terr_2• 2 years ago

The article has three headings which I'd paraphrase as:

1. With their poor eyesight, if they were fast they'd half-blindly get into trouble and fall to their deaths or whatever, so it's kinda-sorta beneficial given that other constraint.

2. Being slow-by-design reduces calorie needs, meaning they can survive eating a smaller amount of stuff and stuff that other animals also don't want as much. This lets them fit into a low-competition niche.

3. Most nearby predators are looking for fast-moving targets, so being slow helps them avoid being detected.

ggm• 2 years ago

This has chicken/egg qualities. Sloths may have poor eyesight because the energy burden and genetic expression behind better eyesight doesn't pay in their niche, but that could imply it's the downgrade option after they slow down, not the input condition which led to slow lifestyle.

Similar to why some small things become giants and some giant things become smalls, it all depends on the niche, and the input conditions before transformation through time and genes.

bradley13• 2 years ago

The article doesn't mention it, but I wonder if there isn't a fourth:

4. Having little muscle mass, and with more than a third of their body weight being half-digested leaves, there's not much worth eating.

Surely a sloth is not the primary prey of any predator. More of a desperation move?

Aardwolf• 2 years ago

Sure but why did poor eyesight evolve, what was the evolutionary advantage?

They hide from predators like jaguars, ocelots and eagles, but why did no predator that grabs them from the trees evolve?

(Just trying to learn from them and their amazing ability to stay under the radar for 65 million years :D)

The_Colonel• 2 years ago

It seems like this article just lists a bunch of facts about sloths.

It's because there's no singular reason for it. Evolution is blind (pun not intended), doesn't have motivation or reasoning. I think the article makes a good job explaining the set of evolutionary forces which likely pushed sloths into this direction.

But doesn’t say why being nearly blind

The article mentions that this mutation already happened to the sloth ancestors, which lived on the ground. It's possible that it provided some advantage to those, or perhaps it didn't actually matter much (perhaps they were nocturnal?)

Log_out_• 2 years ago

Evolution happily trades everything away that would allow to escape the niche your stuck in. And one day, you are a koala, unable to recognize leaves when they are not on branches, a planktonwhale beaching yourselves, a panda who needs electric help to procreate, or a sloth to slow and calorie low to eat. Moral of the story: High effort Low Energy diets are a evolutionary swamp - never eat all your veggies.

roenxi• 2 years ago

But doesn’t say why ... slow metabolism gives any evolutionary advantages

I imagine the author accidentally thought it was obvious. Having a slow metabolism is an evolutionary advantage in the same way not spending money is a financial advantage. It uses little energy and energy is usually the limit on what animals can do. If you don't spend much money, you don't need to earn much and can just exist. Being a high-earner-high-spender is probably a more efficient equilibrium, but spending nearly nothing works well enough to survive and if someone can spend less than they earn eventually they get wealthy.

If sloths don't do much, they don't need to eat much to balance out the energy expenditure. If they don't need to eat much, they can take less risks and tend to survive. Being slow is one aspect of their strategy of not needing to eat much.

fuzzfactor• 2 years ago

why are sloths so slow?

Well they started early and had already arrived before all of us got here.

No reason to get in a hurry after that.

ricksunny2• 2 years ago

Just respecting the creation of an ad-hoc HN account dedicated to getting this evolutionary biology question answered =)

smallerfish• 2 years ago

We had a tree topple in our backyard last year during a rainstorm. Several days later I was working with a crew, cutting it up; one of the gardeners working on the top branches of the tree waved at me and beckoned me over, and when I got there pointed out a sloth, still tightly gripping a limb of the fallen tree. We cut the branch that it was on, and then carried branch and sloth over to the nearest large tree. The sloth relatively rapidly transferred to the trunk of the tree, and then relatively rapidly ascended into the canopy, where we lost sight of it.

Rinzler89• 2 years ago

sloth, still tightly gripping a limb of the fallen tree

Wow. Didn't it get hurt from the tree falling down on it?

rapidly ascended

Doesn't sound very slothy.

MathMonkeyMan• 2 years ago

Save energy except when you definitely need it.

Etherlord87• 2 years ago

"relatively"

teruakohatu• 2 years ago

Sloths almost seem like creatures that evolved on another (slow) world. I wonder if they perceive time differently to us and if their brains are underclocked.

antisthenes• 2 years ago

Maybe they figured out the secret to a Zen life?

bbarn• 2 years ago

Another fun fact about sloths. My wife is curator of a zoo and they have had some in the past. That slow digestion the article mentions? They probably have some of the worst smelling feces of any animal in the wild.

bell-cot3• 2 years ago

Might that be another part of their predator-discouraging strategies?

greentxt2• 2 years ago

I doubt they can control the smell.

shellfishgene2• 2 years ago

Probably not, sloths only poop on the ground, which makes them vulnerable. Related post from the site: https://slothconservation.org/why-do-sloths-poop-on-the-grou...

wombatpm• 2 years ago

Sloths are also the only land mammals that can have more than 7 cervical vertebrae. Any other mammals born with more than 7 die quickly from cancer

lagniappe2• 2 years ago

Hang on, what? Specifically the cancer part

hurtuvac78• 2 years ago

I have seen videos of small turtles going really fast on tiny skateboards. All of a sudden, they become a fast animal and seem happy with it. A bit like human with a bike or a car.

Feels like evolution is not as perfect as we want to believe sometimes.

Could something similar happen with sloths? Maybe their eyesight would improve quickly?

mzl• 2 years ago

Who has ever said that evolution is perfect?

rramadass2• 2 years ago

Interesting article. Given their low metabolism, lack of muscles, low amount of food intake i was wondering where their strength comes from. Thankfully the article links to another fascinating one which explains it - https://slothconservation.org/think-stronger-sloth/#:~:text=....

asimpletune• 2 years ago

I think this is the first time I've seen someone use text fragments in the wild.

anentropic• 2 years ago

in Chrome just right-click and "copy link to highlight"

it's handy for sites that don't put anchors on all their headings etc... or like this to link to random place in body text

marginalia_nu• 2 years ago

Most animals leave a lot of brute strength off the table by how they are designed, because there's more important concerns such as speed and explosivity. Strength is a tertiary concern.

The human biceps is a good example of this. From a mechanical standpoint, where its insertion is like barely below the elbow joint, the bicep has extremely poor leverage, to the point where it needs to exert much more force than the hand does probably by a factor ~20-50. If it somehow went diagonally between the shoulder and the wrist, maximizing leverage, ignoring everything unpractical about this you'd be able to curl a small car engine. The downside is that a diagonal bicep would give us about 40 degrees of range of motion for the elbow and we'd be completely unable to throw things.

Big exception is jaw muscles (which are set up closer to that bicep thought experiment). Since they don't need to "escape" from anything and can sacrifice a bit of range of motion, they can afford to optimize for strength and endurance.

rramadass2• 2 years ago

Nice. I find the evolutionary design, adaptation and body dynamics of the various animal species highly fascinating. With an interest in Hatha Yoga and Martial Arts i also like to figure out how the Human Body can do apparently "impossible" feats of strength. One good example is Shaolin Monks/Circus Strongmen lifting bicycles/tables etc. by biting them with their teeth which can be explained by the natural strength of the jaw muscles due to its anatomical construction as you point out. A couple more are; 1) Mountain Sherpas carrying huge loads using headbands and traditional baskets 2) African/South Asian/South-East Asian rural women balancing and carrying huge loads on their heads all with minimal energy expenditure. These all seem to involve strong neck muscles, a unique posture and gait and proper body alignment.

kaon_• 2 years ago

Fun read! It still surprises me no predator has been able to somehow take advantage of this evolutionary gap. You'd think one of the predators mentioned in the article would evolve a different way to the detect them.

Then again, something similar probably happened many times in evolutionary history, and the victim species died out as a result. So if one of those predators would exist, we wouldn't have sloths. I guess this leaves them vulnerable to invasive species?

amelius• 2 years ago

Turtles aren't particularly fast either ...

cess11• 2 years ago

Leatherbacks can do 30 km/h sprints and they are very good at doing quick turns.

jvanderbot• 2 years ago

I do not understand the downvotes. I watched a half-meter-wide snapping turtle spend all day trundling its way to the water this spring. It looked like one of those world war 1 tanks.

Of course, it had the armor of a tank and a 20 cm neck with a bolt cutter for a mouth.

shellfishgene2• 2 years ago

It's not like they never get eaten by predators, as the article says. It's only that they need ot shift the balance far enough in their favor to not die out, like by improving camouflage.

ajnin• 2 years ago

The article also mentions that they have relatively little muscle mass, so maybe it is more rewarding to catch say a regular monkey rather than a sloth.

Evolutionary traits usually come with a tradeoff, and if a predator evolved to be able to catch sloths more easily it might make them less able to catch the juiciest prey, so overall it might be more worthwhile to focus on the other animals and leave sloths off the table, so to speak.

hcarvalhoalves• 2 years ago

People have been maimed by sloths under the false assumption that, because it moves slowly, it isn’t dangerous. The animal is actually quite strong and can defend itself with the claws.

In Brazil you can visit caves featuring scars on the rock from the pre-historic giant sloth’s claws. This funny animal descends from that!

https://oglobo-globo-com.translate.goog/google/amp/brasil/no...

inSenCite• 2 years ago

Sloths are pretty rad.

But given their lack of thermal regulation, I wonder if this leaves them especially vulnerable to climate change.

kruczek• 2 years ago

This reminds me of the same revelation I had when observing my cat in a backyard. There were many snails around, but my cat seemed completely oblivious to their presence; it wouldn't register them as living animals, because they would move so slowly.

blueyes• 2 years ago

For people who like sloths, I highly recommend the Pygmy Slow Loris:

https://nationalzoo.si.edu/animals/pygmy-slow-loris

In America, you can find them at the DC zoo in a shadowed alcove under red light to simulate night time during visiting hours.

butz• 2 years ago

Why such strange text formatting? Text color seems to change randomly, some paragraphs, words and even part of words are in bold.

bilater• 2 years ago

Obligatory Zootopia Sloth scene: https://youtu.be/HHKwnUa3txo?si=ZblXuDa4RXtYXzzk

veunes• 2 years ago

My spirit animal is a sloth. Manifesting it here

opyate• 2 years ago

TLC;DR

Too low contrast; didn't read

Why Are Sloths So Slow?

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