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