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 108 days 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 108 days ago [-]
Save energy except when you definitely need it.
SV_BubbleTime 107 days ago [-]
They can move very fast.
However… their diet is so calorie low that they can actually really harm themselves by exerting too much energy, basically can’t replace it quickly enough.
They are so evolutionary evolved to move slow, I saw one scared and struggling against a vet that it was still moving in a slow motion defense.
Side note, that vet only had 4.5 fingers on one hand. A sloth bit half of one off years ago in a slow motion amputation. Very sharp teeth (they move slow) and very powerful jaws.
Etherlord87 108 days ago [-]
"relatively"
klondike_klive 108 days ago [-]
It occurred to me for the first time the other day that the word "sloth" is to "slow" what "warmth" is to "warm".
ks2048 108 days ago [-]
According to wiktionary, these are the examples of -th "Used to form nouns of quality from adjectives. (no longer productive except jocular coinages)":
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).
ks2048 108 days ago [-]
As a native English speaker there are words there that I've never seen and others were I would not know the original adjective. In wiktionary, you can click them see etymology, here https://en.wiktionary.org/wiki/-th#English
For example, apparently "filth" comes from the equivalent of "foul".
jeroenhd 108 days ago [-]
> As a foreigner I’m curious what the original adjective was for filth, length, ruth, wealthy, wrath
Looked the ones I didn't know the adjectives of up on wiktionary: foul, long, rue, possibly the archaic "wele" (but there are multiple etymological paths), and basically "wrath" but pronounced slightly differently going back thousands of years.
xerox13ster 107 days ago [-]
Wealthy's root form is weal. As in we should do things for the common weal of the people.
Weal is defined as happiness, well-being, prosperity, or that which is best for someone.
checkyoursudo 108 days ago [-]
Earthy means someone with big ears. Or lots of ears, maybe.
I am a little surprised that ruth is spelled that way instead of like rueth, which seems more like how I would expect it to be said.
108 days ago [-]
musicale 107 days ago [-]
length <- long
strength <- strong
Mordisquitos 108 days 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!
thfuran 108 days ago [-]
I'd prefer we focus our efforts on -le.
SamBam 108 days 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."
brookst 107 days ago [-]
Too many aitches + four consonants in a row. It just looks weird.
SamBam 107 days ago [-]
That's probably the reason for eliminating the written word. Saying "width and heighth" still sounds pretty reasonable (I have to stop myself from saying it), and I hear it all the time.
brookst 106 days ago [-]
Good catch. I do say "heighth" but spell it "height." It's like the opposite of a silent H; an invisible H or something.
endofreach 108 days 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 108 days 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 108 days ago [-]
Apparently it was historically spelled in a way that makes the slow + -th connection more apparent!
And some people do pronounce the word “slow-th” though it’s atypical.
NovemberWhiskey 108 days ago [-]
It’s how it’s pronounced in British English.
bitdivision 108 days ago [-]
No it's not. It's pronounced in the same way as the US, unless you're David Attenborough.
Edit: It seems as though others do say slow-th, but it's not something I've really heard from the younger generation
NovemberWhiskey 107 days ago [-]
The RP pronunciation (i.e. standard British English) is /sləʊθ/ ... i.e. slow-th, and that's how it's indicated in the OED.
HeatrayEnjoyer 108 days ago [-]
[flagged]
vrc 108 days ago [-]
Many would bristle at you referring to Sir David Attenborough as atypical!
Loughla 108 days ago [-]
I was joking around with a student from England who is attending the college I'm consulting with right now. He is trying to figure out a future career. He wants to do something with media. I was throwing out really stupid ideas to get him to laugh. Then I Said, "why not replace Attenborough?"
The joking immediately stopped and he stared at me deadpan and said "not funny. No one could do that."
It was amazing.
Nursie 108 days ago [-]
Yeah, we Brits are very proud of him, a real one of a kind national treasure. But we're also now painfully aware that Sir David is quite, quite old. Born in 1926 apparently. And there really isn't an obvious candidate to fill the gap once he does go.
After having had that voice on well-produced nature content for my entire life, I find most other nature-documentary voice-overs quite jarring. Even the British ones (Tom Hiddlestone had a go recently IIRC).
I will say though that I enjoyed Paul Rudd doing ‘Secrets of the Octopus’. Didn't overplay it, just did a really good job IMHO.
iainmerrick 108 days ago [-]
Tangentially, for the Attenborough fans here, I highly recommend you check out "Zoo Quest in Colour" if you haven't already: https://www.bbc.co.uk/programmes/p03qxfsg
"Zoo Quest" is his first nature documentary series, from 1954(!), very different in style from today's nature shows. I remember as a child seeing clips of it when it was already ancient history -- grainy black-and-white footage of a very young and athletic Attenborough practically wrestling a lizard.
It was originally broadcast before colour TV existed in the UK (funnily enough, Attenborough was the controller at BBC 2 when they pioneered colour broadcasting) so everyone assumed it had been shot in black and white. But in 2016 someone discovered that much of the original footage was colour film. The restored version is absolutely gorgeous.
iainmerrick 108 days ago [-]
After having had that voice on well-produced nature content for my entire life, I find most other nature-documentary voice-overs quite jarring.
Yes! I think it's not just familiarity, what makes him definitive is a combination of factors: fantastic voice and deep domain knowledge and his very clear love and enthusiasm for nature.
You can get an actor with a great voice, Morgan Freeman or Tom Hiddleston or whoever, but you always know they're just reading from a script and probably don't know any more about the animals than you do.
And there are other experts with a knack for presenting, people like Mary Beard, but you can't just transfer that knowledge to a completely different subject area.
luxuryballs 108 days ago [-]
uh oh I can see where this is going given the current technology trends… I wonder if his family can patent the voice or get royalties from a reproduction
Nursie 108 days ago [-]
Oh, I really hope that's not where we end up!
I have lots of time for well-meaning parody though, such as this one about the majestic Australian White Ibis (otherwise known as the bin chicken) - https://www.youtube.com/watch?v=w4dYWhkSbTU
sudobash1 108 days ago [-]
I have always heard this pronunciation in American English when referring to the vice.
jagged-chisel 108 days ago [-]
One of the seven deadly sins
moffkalast 108 days ago [-]
Rule number one: Cardio.
sethammons 107 days ago [-]
so _that_ is why some pronounce it "slow-th" vs "sloth" (that rhymes with cloth)
whyslothslow 108 days 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_ 108 days 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 108 days 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 108 days 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?
ricksunny 107 days ago [-]
(not sure why 'surely')
Aardwolf 108 days 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)
Terr_ 107 days ago [-]
> They hide from predators like jaguars, ocelots and eagles, but why did no predator that grabs them from the trees evolve?
A harmful attribute on its own can be advantageous when combined with others. Think of it as finding a new "local maxima" in the sum total of evolutionary traits. Being (probably randomly) near-blind may have led to being slow and careful, which was the temperament needed to survive climbing trees, which got them away from ground-based predators and found them a lot of leaves ground sloths couldn't reach.
Evolution is basically a random-walk algorithm to find combinations that work.
The_Colonel 108 days 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_ 108 days 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 108 days 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.
ricksunny 107 days ago [-]
Just respecting the creation of an ad-hoc HN account dedicated to getting this evolutionary biology question answered =)
fuzzfactor 107 days 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.
107 days ago [-]
yndoendo 108 days 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.
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.
nsguy 108 days ago [-]
IIRC they also come down from their tree to poop once per week.
TheRoque 108 days ago [-]
And the poop can be up to 3/4 of their total weight
dtgriscom 108 days ago [-]
Wait a minute.... that article says that the contents of their stomachs can be up to a third of their weight. Add 3/4 of their weight is poop, and that's more than 100% of each sloth being either digesting leaves or digested leaves.
at_a_remove 108 days ago [-]
I think that it probably goes like: 0/0, 30/0, 0/25, 30/25, 0/50, 30/50, 0/75, so that one in emptying into the other fast enough to avoid overslothing, assuming 5% goes to making the sloth fatter. This allows for a minimum "neither tummy nor turd" 20% sloth floor value.
If that were increased, we would instead see a series with smaller and smaller non-zero values for fullness as we approach maximum sloth fecalness.
xattt 108 days ago [-]
Fecality factor?
at_a_remove 108 days ago [-]
Sloth stool ceiling.
TheRoque 108 days ago [-]
I made a mistake. It's 1/3, but I think it's included in the "stomach's weight". Sorry
labster 108 days ago [-]
The mathematics works the same way as programming projects: when the task is 90% done you get to finish the remaining 90% of the work.
dumpHero2 108 days ago [-]
Why do they come down to poop?
istjohn 108 days ago [-]
They're not going to risk having it land on some poor unsuspecting sloth below them! That would be barbaric.
bbarn 108 days 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.
wombatpm 107 days 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
lagniappe 107 days ago [-]
Hang on, what? Specifically the cancer part
bell-cot 108 days ago [-]
Might that be another part of their predator-discouraging strategies?
greentxt 108 days ago [-]
I doubt they can control the smell.
bell-cot 108 days ago [-]
Puffer fish can't control being poisonous, but it still discourages predators.
lagniappe 107 days ago [-]
Poor example, they're not naturally poisonous, it's dietary. Palytoxin and Ciguatoxin are not endogenous, the animal first has to eat another organism containing a dinoflagellate that creates these toxins, Gambierdiscus toxicus. This quality is inherent to most reef fish, especially ones with beaks.
bell-cot 107 days ago [-]
> Poor example, they're not naturally...
So...what if the vile-smelling feces of the sloths was not "natural", but due to a variety of microorganisms which had colonized their intestines?
greentxt 107 days ago [-]
Begging the question, nature or nutrition.
CubicsRube 108 days ago [-]
Like tigers can't control their coat color or stripe pattern, but it has an evolutionary advantage so these traits persist.
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=....
marginalia_nu 108 days 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.
rramadass 107 days 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.
asimpletune 108 days ago [-]
I think this is the first time I've seen someone use text fragments in the wild.
anentropic 108 days 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
teruakohatu 108 days 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.
hcarvalhoalves 108 days 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!
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.
kaon_ 108 days 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?
ajnin 107 days 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.
shellfishgene 108 days 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.
amelius 108 days ago [-]
Turtles aren't particularly fast either ...
cess11 108 days ago [-]
Leatherbacks can do 30 km/h sprints and they are very good at doing quick turns.
jvanderbot 108 days 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.
antisthenes 108 days ago [-]
Maybe they figured out the secret to a Zen life?
108 days ago [-]
opyate 96 days ago [-]
TLC;DR
Too low contrast; didn't read
butz 107 days ago [-]
Why such strange text formatting? Text color seems to change randomly, some paragraphs, words and even part of words are in bold.
blueyes 107 days ago [-]
For people who like sloths, I highly recommend the 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.
inSenCite 108 days ago [-]
Sloths are pretty rad.
But given their lack of thermal regulation, I wonder if this leaves them especially vulnerable to climate change.
hurtuvac78 108 days 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 108 days ago [-]
Who has ever said that evolution is perfect?
soneca 108 days 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 108 days 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.
You literally created a new account to post this unsubstantive and obviously strawmannish comment. I am not a mod and have no authority on this forum but we'd honestly be better off without you.
davidmurdoch 108 days ago [-]
That's what we call "grind culture". People like that do exist though, but it's not a majority by any stretch. Maybe it was a few generations ago though.
somekyle2 108 days ago [-]
who is saying this on the behalf of western society?
prashp 108 days ago [-]
This is a question about survival, not productivity.
Wow. Didn't it get hurt from the tree falling down on it?
>rapidly ascended
Doesn't sound very slothy.
However… their diet is so calorie low that they can actually really harm themselves by exerting too much energy, basically can’t replace it quickly enough.
They are so evolutionary evolved to move slow, I saw one scared and struggling against a vet that it was still moving in a slow motion defense.
Side note, that vet only had 4.5 fingers on one hand. A sloth bit half of one off years ago in a slow motion amputation. Very sharp teeth (they move slow) and very powerful jaws.
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
(As a foreigner I’m curious what the original adjective was for filth, length, ruth, wealthy, wrath).
For example, apparently "filth" comes from the equivalent of "foul".
Looked the ones I didn't know the adjectives of up on wiktionary: foul, long, rue, possibly the archaic "wele" (but there are multiple etymological paths), and basically "wrath" but pronounced slightly differently going back thousands of years.
Weal is defined as happiness, well-being, prosperity, or that which is best for someone.
I am a little surprised that ruth is spelled that way instead of like rueth, which seems more like how I would expect it to be said.
strength <- strong
But enough jocularth can eventually result in -th becoming productive again!
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."
Which makes me think: i am surprised that is not an excessively used term in the startup / brotrepreneur world...
https://en.wiktionary.org/wiki/sloth#Etymology
Edit: It seems as though others do say slow-th, but it's not something I've really heard from the younger generation
The joking immediately stopped and he stared at me deadpan and said "not funny. No one could do that."
It was amazing.
After having had that voice on well-produced nature content for my entire life, I find most other nature-documentary voice-overs quite jarring. Even the British ones (Tom Hiddlestone had a go recently IIRC).
I will say though that I enjoyed Paul Rudd doing ‘Secrets of the Octopus’. Didn't overplay it, just did a really good job IMHO.
"Zoo Quest" is his first nature documentary series, from 1954(!), very different in style from today's nature shows. I remember as a child seeing clips of it when it was already ancient history -- grainy black-and-white footage of a very young and athletic Attenborough practically wrestling a lizard.
It was originally broadcast before colour TV existed in the UK (funnily enough, Attenborough was the controller at BBC 2 when they pioneered colour broadcasting) so everyone assumed it had been shot in black and white. But in 2016 someone discovered that much of the original footage was colour film. The restored version is absolutely gorgeous.
Yes! I think it's not just familiarity, what makes him definitive is a combination of factors: fantastic voice and deep domain knowledge and his very clear love and enthusiasm for nature.
You can get an actor with a great voice, Morgan Freeman or Tom Hiddleston or whoever, but you always know they're just reading from a script and probably don't know any more about the animals than you do.
And there are other experts with a knack for presenting, people like Mary Beard, but you can't just transfer that knowledge to a completely different subject area.
I have lots of time for well-meaning parody though, such as this one about the majestic Australian White Ibis (otherwise known as the bin chicken) - https://www.youtube.com/watch?v=w4dYWhkSbTU
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.
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.
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.
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?
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)
Isn't that what the eagles already do? https://www.youtube.com/watch?v=i0zrah5JEBM
Evolution is basically a random-walk algorithm to find combinations that work.
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?)
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.
Well they started early and had already arrived before all of us got here.
No reason to get in a hurry after that.
[0] https://www.goodreads.com/book/show/34211802-the-unexpected-...
If that were increased, we would instead see a series with smaller and smaller non-zero values for fullness as we approach maximum sloth fecalness.
So...what if the vile-smelling feces of the sloths was not "natural", but due to a variety of microorganisms which had colonized their intestines?
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.
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
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...
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?
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.
Of course, it had the armor of a tank and a 20 cm neck with a bolt cutter for a mouth.
Too low contrast; didn't read
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.
But given their lack of thermal regulation, I wonder if this leaves them especially vulnerable to climate change.
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?
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.
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.