The American theologian Harvey Cox wrote an essay, 'On Not Leaving It To the Snake' on how the sin of Adam and Eve can be interpreted as sloth. Cox' argument is that in the myth of the Garden of Eden, Eve let the serpent talk her into eating the fruit, and Adam let Eve talk him into eating. Photos: Snakes and sloths on display at Little Ray's Wildlife Festival Back to video A sloth named Chloe on display at Little Ray's Wildlife Festival being held at Evraz Place.
Conventional wisdom has it that sloths are simple, lazy creatures that do very little other than sleep all day. Even the very name 'sloth' in most languages translates as some version of 'lazy'. It seems astonishing that such an animal survives in the wild at all.
In 1749, French naturalist Georges Buffon was the first to describe the creature in his encyclopedia of life sciences, saying:
Slowness, habitual pain, and stupidity are the results of this strange and bungled conformation. These sloths are the lowest form of existence. One more defect would have made their lives impossible.
Given such a precedent, it is of little surprise that sloths are subject to such profound speculation and misinterpretation, ranging from the benign – that they sleep all day – to the creative anecdotes I regularly hear, such as: 'Sloths are so stupid that they mistake their own arm for a tree branch'.
Sloths can be 60 to 80 cm (24 to 31 in) long and, depending on the species, weigh from 3.6 to 7.7 kg (7.9 to 17.0 lb). Two-toed sloths are slightly larger. Sloths have long limbs and rounded heads with tiny ears. Three-toed sloths also have stubby tails about 5 to 6 cm (2.0 to 2.4 in) long.
The truth is that sloths are incredibly slow movers, but for a very simple reason: survival. The fact that slow sloths have been on this planet for almost 64m years shows that they have a winning strategy. But in order to understand exactly what it is that makes them such slow movers, and why this works so well, we have to look at the biology of these unusual animals in more detail.
Sloth Crawls Over Snake
Three-toed sloths are indeed the slowest-moving mammals on the planet, but exactly how slow is slow? At the world's only sloth sanctuary in Costa Rica, we have been monitoring the movement and activity patterns of wild sloths using small data loggers combined with tracking devices inside specially built 'sloth backpacks'. We've found that, contrary to popular belief, sloths don't actually spend inordinate amounts of time sleeping; they sleep for just eight to ten hours a day in the wild. They do move, but very slowly and always at the same, almost measured, pace.
Moving slowly unequivocally requires less energy than moving fast, and it is this principal that underlies the sloths' unusual ecology.
Sloths are not the only creatures in the animal kingdom to adopt a slow pace. Cold-blooded ectotherms such as frogs and snakes, are commonly subject to enforced slow movement when faced with cold temperatures, due to their inability to regulate their own temperature independently of the environment. Just like any chemical reaction, cold muscles are slow muscles so cold reptiles are slow reptiles.
This is in stark contrast to most homeothermic mammals which maintain a stable, high core temperature via a process of adaptive thermogenesis, and are consequently able to move fast and effectively regardless of the ambient conditions. But this athletic ability comes at a cost: high body temperatures mean high metabolic rates, and somehow the energy bill must be paid using food.
So where do sloths fit into this dichotomy? They move slowly at all temperatures and, unsurprisingly, deviate from the typical homeothermic mammalian plan by operating at lower body temperatures than most mammals, while apparently having a reduced ability to thermoregulate. The average temperature of the three-toed sloth is around 32.7℃ (91℉), compared to humans' 36.5℃/97.8℉.
Much in the manner of ectotherms, sloths depend on behavioural and postural adjustments to control their own heat loss and gain, showing daily core temperature fluctuations of up to 10℃. By perpetually moving slowly and partially departing from full homeothermy, sloths burn very little energy and are able to function with the lowest metabolic rate of any non-hibernating mammal, with estimates ranging from 40–74% of the predicted value relative to the sloth's body mass.
As a result of all this, sloths don't need to acquire much energy or to spend time looking for it. Both two and three-fingered sloths have a predominantly folivorous (leaf-based) diet, consuming material with a notably low caloric content. There are plenty of other mammals which specialise on a leaf-based diet, but usually these animals compensate for their low-calorie diet by consuming relatively large quantities of food. Fellow leaf-eating howler monkeys move at a normal pace but consume three times as many leaves per kilogram of body mass as sloths, digesting their foodstuff comparatively quickly.
Therein lies another sloth peculiarity: for the majority of mammals, digestion rate depends on body size, with larger animals generally taking longer to digest their food. Sloths appear to break this rule to an unprecedented extent. The exact rate of digestion remains unclear, but current estimations for the passage of food from ingestion to excretion range from 157 hours to a staggering 50 days (1,200 hours).
Unsurprisingly, the sloth's four-chambered stomach is constantly full, and so more leaves can only be ingested when digesta leaves the stomach and enters the small intestine. Food intake and, critically, energy expenditure are likely limited by digestion rate and room in the stomach. Indeed, the abdominal contents of a sloth can account for up to 37% of their body mass.
All this points to an extraordinary lifestyle, with sloths living on a metabolic knife edge where minimal energy expenditure is finely balanced with minimal energy intake.
With their plethora of energy-saving adaptations, sloths physically don't have the ability to move very fast. And with this, they do not have the capacity to defend themselves or run away from predators, as a monkey might. Instead, their survival is entirely dependent upon camouflage – a factor aided by their symbiotic relationship with algae growing on their fur. Sloths' main predators – big cats like jaguars, ocelots and birds such as harpy eagles – all primarily detect their prey visually, and it is likely that sloths simply move at a pace that doesn't get them noticed.
The sloth life is certainly not the 'lowest form of existence', but as strategic as that of any other animal. They are energy-saving mammals taking life at a slow pace to avoid the rush and tumble for food, while subscribing the movement patterns that help them avoid being identified as prey. There must be a lesson somewhere in that for all of us.
A handful of indigenous South American tribes, stranded researchers, and illegal dealers of the latino black markets aren't the only ones that love to enjoy the slow twitch muscles of the slowest mammal on earth — the sloth.
Sloth Meets Snake
Wild animals that live around the spaces where sloths are found also find the dark meats on their bodies interesting, although, not necessarily their intestines since they're constantly filled up to capacity with fibrous feaces!
Keep reading discover the fauna of the Amazonia that are heartless enough to make a meal out of a cute sloth.
What eats sloths?
Felid species and harpy eagles eat sloths although the latter is widely regarded as their main predator.
Harpy eagles combine their perfectly developed vision alongside their huge and deadly talons to monitor and snatch up their victims, respectively.
Felid species on the other hand mostly pounce on sloths that are at or near the forest floor, although most of them are known to be terrific climbers too and can easily climb up the distance to retrieve a sloth.
Below is a brief discussion on some of the well known predators of sloths.
The sloth predators
1) Harpy eagle
Harpy eagles are the main predators of sloths. They are the most powerful birds of prey that inhabit the canopy of the Neotropical rainforests.
Their name comes from the ancient mythical creatures, the harpies, which are known for their cruel and destructive nature and are depicted as half vulture, half human in mythological literatures.
As a top predator in the neotropics, harpy eagles feed mainly on arboreal mammals such as monkeys, sloths and porcupines. One study showed that juvenile and subadult sloths accounted for two-thirds of the entire body mass consumed at five harpy eagle nests in Parintins, Amazonas state, Brazil. Only 37% of the body mass found at a nest in Guyana were found to be of arboreal monkeys (Izor, 1985).
On a range, male harpy eagles typically weigh between 4.4 to 4.8 kg, while the females weigh between 7.35 to 8.3 kg — about double the size of their male counterparts.
With these weight and given the strength behind that body, harpy eagles are comfortably able to lift medium-sized mammals like sloths, monkeys and baby deers.
Often, females are the ones that hunt the larger sized mammals while the much smaller and agile males prey on juveniles and and tiny year olds, usually nothing more than 3 kg in weight.
As support for this skillful aerial lifting, harpy eagles have an impressive eye sight and excellent sense of hearing they use for pinpointing their prey.
They are capable of espying on objects as small as a dime from about 200 meters away. They have extremely powerful legs and long, sharp talons designed for stabbing, snatching and firmly gripping on their victims.
For a much larger species of sloths like the two fingered variety, particularly the adult males, harpy eagles prefer to drop them from the safety of the canopy where they reside to the forest floors, in order to inflict serious wounds on them or possibly cause them to perish (highly unlikely).
Then, they feast on their heads almost immediately before taking the remains back to their nests.
Harpy eagles are able to sucessfully kill sloths most of the time because of their strictly sedentary or unsocial lifestyle.
Arboreal mammals like monkeys which mostly live in groups are able to deter away the raptor and prevent it from carrying away any prey by keenly relying on their numbers as an advantage.
Harpy eagles can feed on their kill for several days without falling sick from the rotten carcass. This flexibility enables them to go a whole week or more without hunting down any new preys.
The predation of harpy eagles on sloths and other arboral folivires is thought to have a positive impact on forest regeneration and balance.
By preying on animals that mostly consume leaves and grasses, they help to limit the impact of these herbivores on primary prodcution, which in effect, helps to keep the forests evergreen.
Harpy eagles can grow as tall as one meter and their wingspan can be longer that the height of an average human adult.
Here is a video of a harpy eagle's unsuccessfully attempt on a sloth
2) Felids of the amazonia
Felids (of the amazonia) are basically wild or big cats that live in and around the sloths habitat. They include the likes of jaguar, Jaguarundi, puma and ocelot.
They too prey on sloths but mostly attack ones that are descending from their canopy or have descended from their canopy. They have a wide variety of food resources to choose from the ground which is why their interest for sloths and other arboreal mammals are hugely suppressed.
Felids are top predators and they use their ferocious energy along with their vicious teeth and claws to tear up their preys into bits.
Here is a video of a successful puma attempt on a sloth
3) Other predators
Tayra, large owls, and several snake species have also been observed to prey on sloths in the wild; particularly (for the snakes and Tayras) when they descend to the forest floors to defecate or change environment.
Quick list of the sloth's predators
- Harpy eagle
- Ocelot
- Jaguar
- Puma
- Tayra
- Boa
- Python
- Owl
- Hawk
- Jaguarundi
The sloth's adaptations to predation
Sloths are arboreal folivores, meaning that they live in the crown of trees and are literally embedded in and surrounded by their food at all times and in all directions: they eat tropical leaves and shoots.
High up in the canopies, they survive completely with a short-sighted vision and a rudimentary sense of hearing.
They rely mostly on their sense of smell and spatial memory to actively penetrate their broader environment for food and predatory shelter.
Nearly every aspect of a sloth's arboreal lifestyle is an adaptation to avoid detection by land predators and aerial raptors.
By having the slowest metabolic rate among all living mammals, sloths have very little energy circulating within their system at any given time.
This means that in order to conserve the little energy generated within their body, locomotion must be strictly limited to periods when it's 'only necessary' and has to be in a deliberate and unhurried fashion.
As a result, whenever sloths aren't actively browsing through leaves and selecting from younger branches to feed from, they are found nestled in the fork of tree branches with their heads deeply buried within their chests, or hanging upside down from tree branches by means of their long sturdy claws; externally inactive or deeply asleep.
(Sunquist and montgomery, 1973) observed that wild sloths move an average of seven to ten hours of the twenty-four hours in a day. Such manner of lifestyle effectively conceals their existence and recede their activities from predators.
A cryptic body hair
Sloths have an outer grooved coating of longer thick hair with a dense undercoat of short downy fur.
Several myriad organisms like arthropods and nematodes take up residence in these furs, but not a single one of them (with an exception of the living tribe of algae) confer any sort of anti-predatory benefits.
The living tribe of green algae produce a greenish-tinge on their pelages and cause them to resemble clump of leaves or algae sheltered tree-trunks.
Sloth Lizard
For all sloth species, lethargy and algae camouflage are their main survival strategy and not their biting or clawing techniques.
By incorporating these two tactics and residing high up in the tree canopies, they become notoriously difficult to spot with the naked eyes let alone be suffocated under any savage claws.
Indeed, it took researchers many years to figure out that close to 700 sloths may inhabit one square kilometer of the tropical rainforest (Sunquist, 1986).
Even (Montgomery et al. 1973) were only visually able to locate sloths in their field study five percent of the time, despite the fact that the animals wore radio-collars.
Rudimentary defense
When all the crypticness and grave silence fails to prevent a sloths from going unnoticed by a predator, the next tactic is to resort back to a defensive repertoire packed with meager defensive skills and mechanism: weak clawing, hissing, puffing up hoodwink and biting.
Sloths have 4 inch claws that are long and strongly built. These can cause serious scratches on the body of their aggressors when they swipe at them on the right spot.
Additionally, sloths also have a pointy set of conical teeth that can jab through tissues and leave holes that are large enough to be seen through.
Surprisingly, sloths can run faster than the speed of light when its time to bite or claw at an individual [1].
Despite the fact that sloths claw and bite aggressively when they feel harassed, the miserable strength buried within those slow twitched muscles are no match for the ferocious energy of their hunters.
The perks of extreme adaptation
Such savage form of adaptations in sloths surely comes with a price tag. A heavy one for that matter.
As accommodating as it is in the forest canopies, sloths are virtually helpless on the forest grounds.
Their slow metabolic rate supplies little energy that indirectly confers them invisibility, but also results in an overall reduction and rearrangement of their entire muscle mass.
Muscles require a bulk of energy to maintain and so sloths have evolved an energy-saving tactic to get rid of many redundant muscles and rearrange the remaining ones in such a manner that only befits their lethargic and arboreal lifestyle. (They spend most of their lifetime in the canopy of tropical trees).
Sloths have 30 to 25 percent less muscle mass compared to mammals of similar size. Their bodies are almost completely dominated by retractor or pulling muscles with very fewer extensor or pushing muscles.
Sloth Snake Toca Boca
Their joints also lack necessary supportive tissues and any core stability. This configuration enables them to easily suspend from tree branches whilst expending very little energy, but at the same time, it completely sacrifices their ability to support their own body weight on the ground.
On the forest floors, sloths drag their bodies by finding a hold with their foreclaws and pulling themselves forward using their strong retractor muscles.
In such conditions, and given their lethargic nature, sloths pitifully become they prey animals of even the smallest sized lizards and birds.
Despite being aware of this huge inescapable disadvantage, sloths stubbornly descend from the safety of the canopy to defecate at the forest floor once a week [2].
For whatever reason? Scientist are still trying to make a sense of it. But one thing is clear from a research conducted by Pauli and Peery in 2013, nearly two thirds of all sloth mortalities they observed in a field study happened as a result of depredation event when sloths were at or near the forest floors! [3]. Their predators are of course; harpy eagles, snakes, tayras, medium owls and felids.
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Reference
i) F. Helena Aguiar-Silva 'Food Habits of the Harpy Eagle, a Top Predator from the Amazonian Rainforest Canopy,' Journal of Raptor Research, 48(1), 24-35, (1 March 2014). https://doi.org/10.3356/JRR-13-00017.1
Cite this Article ' (APA Format)
Bunu. M. (2020, March 26). Sloth Predators: What eats sloths?. Retrieved from http://emborawild.com/what-eats-sloths/
