The Insane Biology of: Sloths

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sloths

in the field. The rainforest is a beautiful but deadly place. It is an ecosystem with immensely high biodiversity and intense competition Plants fight for sunlight Insects fight for territory Most animals face the constant risk of death from predation from poisoning from plant diseases or a poisonous sting This ecosystem is suitable so that only the most resistant and formidable creatures remain alive here many prey Animals depend on speed, teamwork or pure ingenuity and yet in all the rainforests of Central and South America lives this creature that is not fast, nor collaborative, and presumably not very intelligent.

Sloths were first described in Western science by the unimpressed French naturalist George Buffon in 1749, he wrote of the slowness, the habitual pain. and stupidity are the result of this strange and failed Confirmation these

sloths

are the lowest form of existence one more defect would have made their lives miserable those sloths are really cute at first glance they have several traits that made Buffon think so little of them Sloths spend their days in the treetops barely moving, when they decide to move they crawl at a breakneck pace of 15 feet per minute, some sloths even spend their entire lives in the same tree they were born in and never bother to venture out. in any direction for any reason.

To some, their continued survival seems like a real mistake, as if an evolutionary blunder had allowed them to go unnoticed, but to view sloths as useless is to view them through a narrow human lens; we humans equate speed and agility with adaptive fitness. , since for our bipedal species these traits have been beneficial for survival in Our Minds The reason something is slow is because it sucks to be fast that slowness is the inferior opposite of speed but lazy people force us to reexamine this paradigm for a sloth, slowness is not a The defect is nothing more than a characteristic and their slow lifestyle is, in fact, the perfect way for them to survive in their dense and chaotic habitat, and the adaptations surrounding the slowness of sloths They are really very strange, from their metabolism to their slow rate of digestion and the muscles in their limbs. bones and fur no other animal is even remotely similar to the sloth because, however strange a sloth may look on the outside, it gets stranger the closer you look.

Modern tree sloths are masters of stealth, a far cry from sloths. domestic animals that originated on this planet. unrecognizable compared to their ground sloth ancestors such as megatherium americanum, one of the largest land mammals that ever existed, weighing up to four tons and measuring up to 6 meters or 20 feet long from head to tail. Unfortunately, these giant sloths became extinct and today there are only six species of sloths, all of them tree sloths from two different families. Two- and three-toed sloths live in or near the canopies of the tropical forests of Central and South America. Their slow, stealthy movement is essential to keep them hidden from predators, such as jungle cats and harpy eagles, these predators hunt primarily by sight, so moving slowly and not making sudden movements helps hide sloths. , but moving high in the trees is not an easy task for any animal.

Moving safely requires strength, agility, and balance, and is an evolutionary challenge that has led to many different adaptive strategies among arboreal mammals. Some species of arboreal animals incorporate their tails into their movement or suspension behaviors. Porcupines, silky anteaters, spider monkeys, and Opossums use a prehensile tail to grab onto branches for additional support and stability. Other animals use speed and momentum to move between trees using a type of locomotion called brachiation. It is mainly used by monkeys and apes and allows them to propel themselves through the canopy by swinging from one point to another with their arms.

It is fast and energy efficient. By swinging like a pendulum, kinetic and potential energy is exchanged back and forth, a brachiant primate can make use of this conservation of momentum and metabolic recovery of energy as it moves, but this locomotor behavior requires a lot of strength if any. once tried it. arm swinging or arm swinging as an adult, like swinging across monkey bars or if you've ever tried one of those hangs for 100 seconds at Carnival scams, you've probably been disappointed with your arm swinging or hanging performance So. It's hard, but even more challenging than arm swing brachiation would be trying to do the bars slowly and even harder than hanging for 100 seconds would be hanging for 10 minutes with one hand.

Sloths that do not have a supporting prehensile tail and do not use pendulum exchanges. of energy to make things easier for them they do all this routinely apparently with the greatest of ease a sloth can easily suspend the entire weight of his body from a single limb for more than 10 minutes he can hold himself between two branches in a crucifix position for even longer So with just a back-of-the-envelope calculation, I discovered that a sloth is about twice as strong as an average human, and yet when you look at their limbs, their muscles are thin and wiry, they don't look like they're strong enough to understand. .

The puzzling strength of sloths I spoke to Dr. Mike Butcher, professor of zoology and biomechanics at Youngstown State University, their total body skeletal muscle mass is only about 23.5 to 24 percent compared to you, you have 44 percent, so they have significantly less muscle, so per gram of muscle tissue, they are getting a lot of strength from their muscles, so how can they perform such feats of strength by dissecting, mapping, weighing and measuring each of the 50 two muscles found in the forelimbs of three-toed sloths? To get closer to an answer, they started by examining all four limbs, where there are two main groups of muscles: the flexors and the extensors, the flexors work to bend a joint, for example, when you flex your biceps, the elbow flexors contract and pull of the forearm segment, creating a flexion or rotation movement of the elbow joint to move the hand upward.

The flexor muscles are used for pulling. Movements like doing pull-ups. The extensors serve the opposite function: extending and straightening the joints. These types of muscles are usually used for pressing movements when you and I are. When walking we are an upright mammal, we expect our extensor muscles to be the most important to keep us upright and support our body weight, but in sloths this story changes completely when you are upside down, those muscle activations must change accordingly. as if the nervous system had to reconfigure or restructure to now use the flexor muscles as the main support muscles in sloths, the flexors are better developed than the extensors, this means that the muscles that sloths use for grasping and pulling are larger Researchers also discovered that the type of individual fibers within the muscle helps give the sloth notable grip strength.

The muscle fibers in the digital flexor musculature become progressively more angled towards the forefoot when the fibers are aligned in this way, which is less parallel to the length of the muscle belly they can produce more force This phenomenon is known as penalty but it is not just how The sloth's muscles are built, which gives them incredible strength, but how they use them. The force-speed relationship is a fundamental principle of skeletal muscle physiology. The data in this curve shows an inverse relationship between force and speed. , meaning that an increase in force would cause a decrease in speed and vice versa and the faster a muscle contracts, we call it contractile speed, the less force a muscle is capable of producing, so what?

Do you think the strategy that sloths have adopted is that they can follow their muscles very slowly, so if you contract the muscle more slowly you are improving the amount of force you can get from them and it has the cost benefit of not consuming a lot of energy to contract their muscles slowly and vigorously, for these reasons three-toed sloths have a relative grip strength that approaches 100 of their body weight; By comparison, the average grip strength for a human being is about 25 to 45 percent of their body weight, which may explain why we don't do so well at those carnival tricks of hanging for 100 seconds with all these surprising adaptations.

Sloths can move through the canopy with surprising acrobatic grace and hang for basically indefinite periods of time, but things don't always go well during sloths. Dr. Becky Cliff is the founder of the Sloth Conservation Foundation and has studied sloths for many years. One of her projects examines the movement and behavior of sloths using small backpacks with radio transmitters and when she started the project, she kept receiving surprising signals of what we would receive. from the backpack data run it would have these cute sloth climbing signals and then it would make a buzzing sound and you would say what happened um and it took us a long time to figure out what these crazy signals were, but it was the sloth falling tree and each individual does it in average once a week for their entire life and they don't fall from a short height, they fall from like 100 meters in the air um and they bounce a little bit when they hit the ground and then they get up and climb the tree again and they're absolutely fine but the sloths don't fall because they lose their grip they simply miscalculate a little which branches to climb on they like to eat the leaves at the tips of the branches and these branches are very flimsy and don't usually support their weight, so they often fall simply because branches break, and fortunately, their ribs are remarkably flexible, allowing them to survive these falls.

The two-toed sloth even has 46 more than any other. Another mammal for reference we have 24, but if it weren't for the sloth's strange diet, they might not run these risks at all. Sloths are deeply particular creatures even though there are hundreds of types of vegetation in rainforests. Three-toed sloths generally only eat. the leaves of some types of trees and of these leaves they prefer the younger leaves that grow in the crowns of the trees eating leaves and only leaves is a rather difficult way to obtain nutrition the leaves have a high proportion of mature and difficult to digest cellulose Leaves don't have many calories, so how does this strategy work for them?

The key to everything is its four-chambered stomach. The first three stomachs are fermentation chambers where symbiotic bacteria break down the leaves and the resulting product is then decomposed. in the fourth stomach by acids and enzymes, this is a lot like how cows digest their food, but usually fullivores compensate for the low calorie content of the leaves by eating a lot and digesting them quickly, but sloths don't have that option. Up to 50 days for them to fully digest a single leaf and this slow digestion means they also only need to defecate once a week, and they obediently climb all the way down the tree to make one of the only reasons they would ever leave. the trees and once they are relieving themselves they make sure to do it in style, the poop dances, something that all sloths do when they go to the bathroom, which they only do once a week, so they climb down from their favorite tree. the poop dance on the floor that looks like they are twerking in slow motion, what they are actually doing is trying to dig a small hole using their butt to move and then poop in the hole and then they do it. another poop dance to bury it and they climb the tree again, but it looks absolutely ridiculous.

It is believed that the reason for this Herculean effort just to poop is to hide its smell. Poop falling from the treetops would leave quite a scent trail. Predators go straight to the perpetrator of that smell and even though they only poop once a week, their stomach is literally always full, they can't eat more until what's in their stomach has already passed, just like everything else, They have to eat their food slowly three times. It has been observed that sloths eat on average only 17 grams of food per day, which is equivalent to three leaves per day.

Eating so little food would starve any other mammal of similar size, but sloths have anothertrick up their sleeve: they have the slowest one. The metabolism of any mammal in the animal kingdom is rivaled only by mammals in deep hibernation. Having such a slow metabolism means they have tremendously low energy needs. Three-toed sloths burn just 130 calories per day. The two lazy toads consume around 300 calories per day and their metabolism is even stranger than it seems at first glance. The first strange thing is that sloths do not need to maintain a stable internal temperature like most other mammals, but rather their internal temperature changes with the outside temperature and can fluctuate by up to 10 degrees Celsius.

This is more like how ectotherms function like lizards, also known as cold-blooded animals, by allowing their body temperature to fluctuate with the outside temperature. Sloths save a lot of energy up to about 32 degrees Celsius. Lazy people would convince you that they are cold-blooded. creatures, but hotter than this point, things get even stranger again, as sloths do something different to any other animal: they begin to actively depress their metabolism without entering a state of aestivation, as far as we know, this is Completely unique in the animal kingdom, enter aestivation. or hibernating would mean turning off almost everything, reducing heart rate, drastically reducing body temperature, and becoming unresponsive.

It is a long and serious process for an animal to do this, but sloths manage to reduce their metabolism quickly while they are awake and able to move. They can also do it for very short periods and can reverse it as soon as the temperatures drop by depressing their metabolism, at the same time they are saving energy and also reducing the amount of metabolic heat their body produces, therefore staying a little cooler, Like sloths, they are ectotherms or endotherms, the answer is that neither or perhaps both exist in a transitional state between cold blooded and warm blooded, a state called heterothermy and while saving energy by moving slowly digest slowly defecate infrequently It clearly has its adaptive benefit.

It also has some surprising side effects. Side effects that look like a curious Quirk but actually provide another layer of protection for the sloth. Staying hidden is the only way sloths can survive and sloths have become true masters. of camouflage, their slow movements allow them to blend in with the swaying branches and also their mossy green fur, a fur so unique that it is its own microcosm of abundant life. Both types of sloths have a diversity. collection of microorganisms on their fur, including arthropods, fungi, and algae, including some species that only exist within the sloth's onboard ecosystem, cryptosis moths, or certain species of green algae only live on sloths' fur, the individual hairs of Three-toed sloths have unique crevices that allow the hair shaft to become saturated with rainwater and allow algae to grow hydroponically.

The algae live their life going directly from the mother sloth to the baby sloth and have not been found anywhere else. Beyond the sloth's fur and, interestingly, in a roundabout way, that silly sloth poop dance. can play a crucial role in the growth of these algae when sloths descend to the ground and defecate, female kryptosis moths lay their eggs in the fresh excrement, the larvae then fully develop inside the feces and the adult moths emerge and fly away into the canopy in search of their Moths probably transport nitrogen from the dung piles, allowing algae to grow, and it turns out that these algae are very important to sloths;

It was recently discovered that they actually consume their algae gardens to supplement their limited diet without the poop dance there would be no moths and without the moths there would be no nitrogen and therefore there would be no algae and for researchers sloth poop may be the key for future research, so one of the projects I'm working on right now is trying to train a dog to detect sloth poop and then we can start walking transects and say, oh, a lot of sloths live in this area based on the number of piles of poop on the floor, um and for the first time we can start to monitor populations over time and see how they're changing and then we can show for the first time that sloths are in trouble, They are actually declining because current conservation statuses do not reflect that and that is based on a lack of data.

Sloths are currently in the least concern category due to this lack of data and without sound science it is difficult to protect these. amazing animals, it's very difficult to get funding for an animal when they say, oh, it's a vague concern and therefore no one cares, but actually, that's not true and what we're seeing here is that sloths are literally decimated in areas where I knew there were sloths living three years ago at really high densities and I've completely nullified our sloths so we literally see it every day and there's nothing like documenting this to governments or the community at large, to funders and donors.

There's just nothing out there. It will take tons of data, tons of documents and hard numbers to ensure the survival of these incredible animals and hard numbers on paper. as these are presented on clean white paper format with black ink, but the way these particular numbers are compiled is never so neat that the field work is the beautiful, messy reality behind much of the science we all know today . I studied

biology

at university. With the law of hours spent in the laboratory and many hours writing articles, everything was very good, but it was not until my first field research trip to Indonesia that my soul was ignited, each day was full of adventures, both good and bad.

I learned firsthand that collecting valuable data on critically endangered frog populations involved walking through rivers at night, stepping on piles of ferocious fire ants, getting caught in powerful storms, stumbling upon magnificent, enormous pythons. This was the science that got me and people excited. Those who do this for a living are some of the most fascinating people I've ever met, their stories are literally crazy, from flesh-eating bacteria to homicidal elephants, to naming new species and seeing places no one has ever seen. Fieldwork is the backdrop to some of the most incredible stories I've ever heard and our new Nebula Plus series field notes aim to capture these exact stories.

I often talk about the science of incredible animals on this channel and now we'll hear from the experts behind that science, the people who spend months. years or decades in the field, the people who know these animals better than anyone on the planet. I recently returned from Costa Rica, where I had the incredible opportunity to witness the work being done there to study and conserve sloths, from tracking them to analyzing their muscle contractions to learning about all the enormous efforts being made to protect them. It was a trip that opened my eyes to the very complicated and rewarding world that is sloth science.

The video you just watched explains the science of sloths in field notes. The episode will show you the sometimes hilarious reality of trying to get that science and since we've been ramping up production like there's no tomorrow, we also have the next episode on becoming human available in the nebula right now, This is about the first tools that our ancestors had. They were made once our ancestors stood upright, hands were free to begin altering the world around them, but the fossil record tells us that the evolutionary leap toward tool-making is not as simple as you might think. we are producing these nebula videos if you have ever done it. considered registering now is the time to do it abroad