Baby Sloths: Everything you always wanted to know

Baby Sloths: everything you always wanted to know!

A baby sloth is fully reliant on it’s mother to teach it how to survive in the canopy of the rainforest. They are fragile yet fascinating little creatures, and here you can learn everything you ever wanted to know about baby sloths!



Giving Birth to a Baby Sloth

A two-fingered female sloth will give birth to a single baby after a gestation period of 11.5 months, while a three-fingered sloth is thought to give birth after approximately six months. Biologists have never had the opportunity to follow a three-fingered sloth all the way from conception to birth, and so this gestation period is still only an approximation.

When it’s time to give birth, the mother will usually descend to the lower canopy branches and give birth while hanging upside down. In this position, if the baby falls to the ground, it won’t fall far, and the mother can climb down to retrieve her young.


baby sloth birth
A three-fingered sloth after giving birth, Costa Rica / Photo: Agustín Murillo


The afterbirth usually falls to the forest floor and female sloths have been known to descend to the ground to consume it – it is very common for animals in the wild to ingest the afterbirth, even herbivores like sloths, probably for a nutritional boost or to avoid attracting the attention of predators.

Occasionally, sloths have been known to give birth to twins, but there is only enough room on the female’s chest for one baby and the sloth’s very slow metabolism only provides enough resources for one, so the weakest twin will usually be rejected.


Baby Sloth Features

A baby sloth is born ready to face the world with eyes open, sharp claws, and fully formed teeth. It will instinctively cling to it’s mother’s fur immediately after birth and crawl up towards the safety of her chest where she begins the process of cleaning the young with her mouth.


baby sloth
Three-fingered sloth (Bradypus variegatus) newborn baby (less than 1 week old) clinging to mother. /Photo: Suzi Eszterhas.


The weight and size of baby sloths differs between the six extant species.  Three-fingered sloths are smaller than two-fingered sloths. A newborn baby sloth typically weighs between 300 – 500 grams, with three-fingered babies often weighing less than two-fingered babies.


baby three toed sloth
This three-fingered sloth is a 2 day old orphaned baby/ Aviarios Sloth Sanctuary, Costa Rica / Photo: Suzi Eszterhas

How much do baby sloths sleep?

Despite the common myth that a sloth will sleep for 20 hours per day, adult sloths in the wild actually only sleep for an average of 8 to 10 hours per day.

Currently, no research has been conducted into the sleeping habits of wild baby sloths, however, if we extrapolate data from other mammals, we can hypothesize that baby sloths will sleep for a larger portion of the day than adults as they do not have to be on the constant lookout for predators or forage for food – their mom’s do that for them!

Adult and baby sloths in human facilities (zoos/rescue centers) sleep for an average of 15 hours per day.


baby two toed sloth yawning
Cute baby two-fingered sloth yawning after a hard day of… sleeping.


Raising a baby sloth

Male sloths, as with most mammals, don’t care for their young. The female sloth will spend up to 12 months of her life raising her baby alone.

The baby clings on the mother’s chest for approximately six months, regularly suckling small amounts of milk throughout the day.


baby sloth pale throated nursing
Pale-throated sloth (Bradypus tridactylus) mother and three-month-old baby / Sloth Island, Guyana / Photo: Suzi Eszterhas


Sloth mothers don’t store large amounts of milk like most other mammals – carrying a heavy supply of milk around is expensive in terms of energy. Because baby sloths are always clinging onto their mother’s chest, females save energy by slowly producing small amounts of milk throughout the day instead.

As well as drinking milk, baby sloths will begin to sample leaves from around their mother’s mouth from as early as 1 week old – this is how the baby learns which leaves are good to eat!


baby sloth eating leaves with mom GIF


Exploring with mom

While young baby sloths usually spend the majority of their time on their mother’s chest, they will occasionally cling onto the fur on her back. This usually happens while she is crawling across the ground, however, as the baby grows it will begin to move around more, and will often take this opportunity to explore what is going on around mom.

At first, this will be reaching out to grab different leaves and branches with two or three limbs, still maintaining a connection with mom, but as the baby slowly gains confidence (and becomes too heavy for mom to carry), they will spend an increasing amount of time next to mom, rather than clinging to her.


baby sloth luna sol
This is Luna and Sol (Moon and Sun) and they are part of our Urban Sloth Project.  On the ground, Sol will climb onto his mom’s back, but he is usually hidden from sight when they are up in the trees as he will curl up into Luna’s chest. Recently, we have been seeing more of Sol as he grows more adventurous.


Learning to poop

Once a week, the mother will climb down to defecate at the base of a tree. The baby sloth will start pooping following the patterns of the mother.

The ‘poop dance’ is something that all sloths do immediately before and after they defecate, and it involves wiggling around at the base of the tree. This dance helps them to clear a space in the leaf litter for them to defecate into, and then cover up the evidence of their weekly journey to the ground afterward. Three-fingered sloths are particularly good at this as they have a short stubby tail that helps to dig a deeper hole!



Falling from the trees

Sometimes a baby sloth will fall from its mother’s chest to the ground where it is very vulnerable to predators.

Sloths are built to survive falls of up to 100ft to the forest floor – however, they are not adapted to fall onto concrete or roofs. As more of their jungle home disappears, sloths are less likely to survive falls.

When a baby sloth falls and becomes separated from mom, they will cry to alert their mother to where they are. Mom will climb down from the canopy to retrieve her baby, but as sloths have a top speed of 2mph, this journey will take a lot of time and energy.


sloth ground
The ground is not a safe place for a baby sloth.

Reuniting with mom – with the help of humans!

In urban areas, well-meaning members of the public may assume that a baby sloth on the ground is in trouble, and will take them to a rescue center before mom has the chance to reach her baby. Rescue centers have developed a technique to reunite mothers with their babies in these situations, by recording the baby’s cry and playing the recording on a loudspeaker where the baby was discovered.

Baby sloth cries are loud, but the jungle is louder (especially in urban areas where cars and construction noise pollute the air). If mom is still around, she will spring into action and slowly head towards the cry coming from the loudspeaker. The lost baby can be placed on the tree trunk once mom is close enough, and mom can scoop her baby up and return to the canopy.


sloth mom mother


However, if a baby falls from mom too many times, mom may stop retrieving them. This is because a mother will perceive something wrong with a baby who cannot hold onto her fur consistently, and with survival being the name of the game in the wild, a mother who has an indication that her baby is not completely healthy is likely to reject them.



There have been reports from rescue centers that mother sloths have come down from the canopy to their babies, only to sniff them and climb back up without the baby, showing the baby sloth has been truly rejected by the mother. In this case, there is a high risk that the baby has congenital abnormalities. Not to mention, climbing up and down from the canopy repeatedly exerts a large amount of energy from a sloth who does not have much to spare!



cute baby sloth climbing learning GIF
Rescued baby sloths learning to climb.


What should you do if you find a baby sloth close to the ground? Keep watch until nightfall, unless the baby is in immediate danger from predators. If 12 hours have passed with no sign of the mother, please contact your local rescue center.

Crying Baby Sloth

Sloths are usually silent creatures as their greatest survival techniques are camouflage and stealth. However, baby sloths will call for mom when they are separated, and this creates some of the cutest sounds and noises imaginable.

Three-fingered baby sloths make a high pitch squeak, while two-fingered babies sound like baby goats (they ‘meep’).



Baby Sloth Diet

As a baby sloth grows, it learns what to eat by copying exactly what its mother is eating. At first, the baby will eat the food from around the mother’s mouth. As it gets older, it will begin to reach off of her body to grab leaves for itself while she is feeding. Through this process, the baby sloth will learn essential lessons about which tree species are safe to eat.


baby sloth feeding image picture
Three-fingered mother and newborn baby (less than 1 week old) feeding from Cecropia leaves / Photo: Suzi Eszterhas


Although sloths are known to feed from more than 90 different tree species, an individual will rotate among approximately seven to 12 favorite feeding trees – a strategy that prevents them from overeating specific toxins present in the leaves. When babies begin to eat leaves fresh from the trees, rather than mulch from their mom’s mouths which are already partially broken down due to enzymes in her saliva, mom will direct her baby to the youngest, most tender leaves of the tree.


Sloth mother
A sloth mother feeding on Cecropia leaves while her baby is watching / Photo: Suzi Esterhas


Not only do these young leaves have lower levels of any potential toxins, but the cellulose cell wall of the plant is less well established in young leaves, making them easier to digest.

Due to their incredibly slow metabolism and rate of digestion, if sloths were to feed from the same tree species for too long, it is thought that they would intoxicate themselves. Sloths learn this behavior and inherit their feeding tree preferences from their mothers, which may be why releasing hand-reared sloths into the wild can be particularly difficult.


Baby sloth eating flower GIF
Hibiscus flowers are like candies for baby sloths, and common food in rescue centers and sanctuaries.

Green Offsprings

Baby sloths will look very different from their mothers when they are born. Adult sloths tend to have some algal and fungal growth on their outer fur, whereas babies are born with only the soft, downy undercoat. They develop coarse outer fur at sexual maturity.

Wild sloths begin to develop their green color after approximately 18 months, as algae, fungi, and insects pass from mother to offspring. For this reason, sloths raised in captivity do not develop the famous green coloration, as they are not interacting with any wild sloths who do have flora and fauna growing on their fur.


young offsprings
These young sloths raised by humans haven’t yet got algae growing in their fur. 


Becoming Independent

At about six months old, the baby sloth will begin to venture off the mother’s body and spend more time hanging out close by. As independence draws closer, the distance between mother and baby slowly grows.

Eventually, the mother sloth will completely leave her original home range and move to a neighboring patch of forest. This is an unusual method of separation for a mammal, as typically the baby is expected to disperse and establish a territory elsewhere.


baby pygmy sloth
Baby pygmy three-fingered sloth (Bradypus pygmaeus) hanging on a tree close to its mother. / Photo: Suzi Eszterhas


Three-fingered sloths weigh 1 – 1.5kg once they reach independence, while two-fingered sloths weigh closer to 2kg.

After separating from its mother, the juvenile sloth becomes solitary and will only choose to interact with others when finding a mate. And now the baby sloth life cycle is completed.


Juvenile sloth and mother
A juvenile two-fingered sloth (Choloepus hoffmanni) in the same tree as its mother.


A rare case: three-fingered sloth ‘adopts’ a two-fingered sloth baby

Cross-species adoptions in the wild are exceptional events, and very rare to see. At the end of 2020, we received a highly unusual report of a three-fingered female that adopted a two-fingered baby in Costa Rica.


Three-fingered sloth 'adopts' a two-fingered!


The reasons behind this behavior are still unknown, and at the moment there are no reports of a similar case. According to the naturalists that were following them on a daily basis to gather data and information,  they looked very comfortable together. You can read more about this case here.


How to make a baby sloth

Sloths reach sexual maturity at approximately two years old. However, when you are a slow mover without much energy to spare, finding a mate can be difficult.

Female three-fingered sloths have found an unexpected solution to this problem – they scream! When she enters estrus, a female will emit high-pitched vocalizations to attract the attention of males.



Two-fingered sloths do not vocalize. Instead, both males and females mark their scent by rubbing their anal glands against tree branches to send messages about their reproductive status.

While sloths will typically only descend from the canopy to relieve themselves once a week, a female sloth will make the long journey down to the forest floor every single day when she is in estrus. Pheromones present in urine and feces are an incredibly important method of communication for all types of sloths and are likely the reason behind their unusual defecation habits.


What is the name of a baby sloth?

There are a lot of names for babies of different animal species: calf, kitten, fawn, cub, piglet, duckling, etc… but we don’t yet have a specific name for a baby sloth! Scientists, biologists, and zoologists usually use the generic words  ‘offspring’, ‘young’, and ‘baby,’ of course.

The Sloth Sanctuary of Costa Rica suggests the word ‘Slowbie’ to refer to a baby sloth.


 kissing kisses
A two-fingered sloth and a three-fingered sloths touching noses before kissing each other.

Baby sloths in captivity

Raising rescued young sloths in the nursery, a rescue center, or zoo is difficult for a variety of reasons.

No one has collected a large enough sample of sloth milk for thorough analysis, as mothers produce milk drop by drop as needed by their baby. This makes it very difficult to know what rescue centers should be feeding orphaned babies!

Most have found that a mixture of mineral water, pureed vegetables, powdered goat’s milk, and supplements can provide an alternative for orphaned sloth babies. 

Sloths are not able to digest the large fat particles found in cow’s milk, and so this can be fatal if fed to them by mistake.


baby sloth feeding eating milk
Rescued two-fingered sloth (Choloepus hoffmanni) drinking goats milk from a specialized syringe


As mentioned above, sloths eat a wide variety of leaves, and it can be a long process to find the right leaves for each sloth. The broadness of their palate is hypothesized to correlate with the trees the baby was sampling from their mom’s mouth. Choosing leaf species present in the area the sloth was found can help with picky eaters, however, rescue centers are limited by time and resources, and the selection of leaves is based on the availability of trees in the proximity of the rescue center.

In addition, baby sloths will often refuse to eat older leaves (which are the most readily available for rescue centers), and the leaves must be freshly cut. This creates a huge daily job for the facility, which takes up a lot of time and resources.

Rescue centers will release the now-rehabilitated adults in areas with an abundance of the tree species they were most fond of in captivity.


baby sloth feeding
Bottle-feeding a 2 day old orphaned newborn three-fingered baby (Bradypus variegatus) is a skilled task. / Photo: Suzi Eszterhas


Cuddly toys and blankets

Baby sloths cling onto their mother’s fur for the first part of their lives. Baby sloths have a biological need to hold onto things due to the structure of their muscles – it is this characteristic that makes sloths so well adapted for life in the trees!

In captivity, baby sloths do not have their mothers to hold on to, which is an extremely stressful experience for them. Baby sloths calm down immediately when given something to hold on to.

In fact, recording a baby sloth’s cry for the purpose of attempting to reunite them with their mother is often done by simply removing whatever the baby is clinging to. To satisfy this need, a rescue center will use stuffed toys and blankets to replace the mother.


orphan blanket
In case you need it, here’s a selection of smiling baby two-fingered sloths (Choloepus hoffmanni) wrapped in blankets


 After a quarantine period to ensure the baby is not carrying any disease which can be passed onto other sloths, a common technique is to put several orphaned babies together, where they become like magnets to each other. This not only allows the babies to hold onto another living, breathing sloth but also aids in maintaining their core body temperature.


baby sloth too cute pics
Hoffmann’s two-fingered Sloths (Choloepus hoffmanni) hugging each other for comfort / Photo Suzi Eszterhas


Baby sloth kisses!

It is also quite common to see rescued baby sloths kissing each other. While it’s tempting to anthropomorphize these baby sloth kisses as affectionate, it’s likely that this behavior is being displaced from sharing leaf-mulch from their mother’s mouths. Wild sloths will also sometimes share ‘kisses’ like this which is thought to be a way of transferring important gut bacteria and enzymes that aid in digestion.

Baby sloths are often seen suckling on other baby sloths’ ears, which is also thought to be a displacement behavior from suckling on their mothers in the wild.  However, it is likely that baby sloths will only perform this behavior if they are comfortable and experiencing very little stress.


baby sloths kissing mom kissing baby GIF
Mother cleaning and kissing her baby.


The problem with orphaned baby three-fingered sloths:

Rescue centers receiving orphaned baby three-fingered sloths are still trying to find the correct protocol to raise the species to adulthood and prepare it for release into the wild. There is currently only a handful of institutions that are able to raise orphaned three-fingered sloths successfully, and unfortunately, very few of these have been considered appropriate for release back into the wild.

Zoos featuring sloths only display two-fingered sloths, usually Linnaeus’ two-fingered sloths (Choloepus didactylus). This is because two-fingered sloths are much more successful in captivity than three-fingered sloths, with the Bradypus species having exceptionally short lifespans in captivity.


Three-fingered sloths are very fragile and hard to keep in captivity.

Do baby sloths get used to people?

Sloths do not humanize in the same way as other mammals, and it has not been reported that orphaned sloths raised in captivity become attached to their carers. Sloths do become desensitized to the presence of humans, and current reports from rescue centers that have released captive-raised sloths have shown that these sloths are attracted to the presence of people.

It is not thought that humanized sloths seek out humans for affection, but it is more to do with seeking out what is familiar. Sloths are creatures of habit, and the inappropriate protocols for raising orphaned baby sloths within some rescue centers does not properly prepare them for life in the canopy, leading to an increased amount of human-animal conflict. When platforms and human food, such as vegetables, are provided throughout the raising process, and little preparation for life in the wild is conducted, sloths will often seek out human habitations, as that is what they know to be ‘safe’.


sloth mom clinging
We like to think that the baby sloths need us and love us, but the truth is the opposite of that! /Photo Suzi Eszterhas


Sloths do not show affection towards people, and in fact, may even actively dislike people. Studies have shown that human physical contact with captive-raised sloths who are desensitized to human presence will still trigger a stress response.

It is for these reasons that rescue centers are advised to have as little physical contact with the sloths as possible, utilizing the babies’ biological need to hold onto something by transporting babies on stuffed toys to avoid any physical contact with their carers. Baby sloths will place themselves on their toys for feeding, replicating the position they would be in to suckle from their mothers.


 fight GIF cute pics
Although they need each other, baby sloths fight a lot!


Can I have a pet baby sloth? Can I buy a baby sloth?

Owning a baby sloth is wrong for a multitude of reasons. Firstly, as mentioned above, it is very hard for even professional wildlife carers to keep baby sloths alive, and raise them for release.

Sloths are not affectionate creatures by nature, and while they may form bonds with each other as babies, this will usually disappear by adulthood. Sloths become extremely stressed when experiencing human contact – their smiling faces are deceptive, they do not show many outward signs of stress. Swiping is one way that sloths exhibit stress, and even this is often misinterpreted by humans as ‘waving.’


Sloth Selfie A.K.A Slofie | Bored Panda
In this viral photo, the young sloth is showing signs of stress. The arms open means they are in defensive behavior.


Sloths can be up to three times stronger than a human being, and can cause significant injury to people if given the opportunity. Two-fingered sloths, who fair better in captivity than three-fingered sloths, also have four razor-sharp pseudo canines which will easily slice through human flesh.


sloth teeth pet
These are still just baby teeth. The bite of an adult sloth is very painful and can be dangerous.


Sloth adoptions!

However, you can still symbolically adopt a sloth for you or a loved one! You can choose physical, virtual, or VIP packages! 100% of the proceeds of these adoptions go towards funding our conservation programs to protect sloths in the wild.

Adopt a Sloth


Baby sloth hugging toy GIF


Looking for something else that is full of cute baby sloths? The Official Sloths Wall Calendar, with interesting sloths facts written by Dr. Rebecca Cliffe and adorable photos by wildlife photographer Suzi Eszterhas! Proceeds from the calendar also go directly towards helping sloths in the wild!


Sloths 2021 Wall Calendar


Searching for the Elusive Maned Sloths of Brazil

Searching for the Elusive Maned Sloths of Brazil

If you are a fan of sloths, you might think that there are two main types:

  1. Two-fingered sloths with their blonde fur and quintessential pig-like noses. There are two different species within the Choloepus genus.
  2. Three-fingered sloths with their mottled grey fur and iconic black ‘masks’ around the eyes. There are currently four different species of three-fingered sloth all grouped together within the Bradypus genus. 

But scientists are starting to realize that there is actually a third type of sloth. One that has the size, strength, and ferocity of a two-fingered sloth, but the physical appearance of a three-fingered sloth.


maned sloth brazil
Photo: Cecilia Pamich – The Sloth Conservation Foundation


It is a species that no one really knows anything about, and one that scientists think is so unique that it might belong in a completely separate genus (called Scaeopus).

These are the maned sloths of Brazil, and they are the most endangered species among the continental sloths. 

What are maned sloths? 

Maned sloths (Bradypus torquatus) are technically a species of three-fingered sloth, but they look and behave very differently to the three-fingered sloths that you might be used to.

Current research suggests that they separated off from the other sloth species approximately 19 million years ago and have been evolving independently ever since. 


maned sloth taxonomy brazil
Current Taxonomy and phylogenetics of Xenarthrans. The green circle shows the moment when maned sloths split off from the other species of three-fingered sloths / Image: Professor Gastón Giné


Unlike the other species of three-fingered sloths, the maned sloths are much larger with brown, fuzzy fur, and dark, hairless pads on their hands and feet (similar to the hands of two-fingered sloths).


maned sloth hand feet brazil
The hand and foot of a maned sloth. /Photos: Cecilia Pamich – The Sloth Conservation Foundation


They lack the iconic black mask around the eyes and male maned sloths do not develop a speculum.


maned sloth brazil

Instead, both males and females of this species have spectacular long black manes of hair that tumble down around their necks and shoulders.

Maned sloth brazil
Maned Sloth with a GPS backpack / Photo: Cecilia Pamich/ Sloth Conservation Foundation


Working together to save sloths

While our SloCo headquarters are based in Costa Rica, we are committed to conserving and protecting all 6 extant species of sloth that are found throughout South and Central America. 

Last month we were delighted to form an exciting new collaboration with Professor Gaston Giné and the Instituto Tamandua in Brazil to carry out important new research into maned sloth ecology.  


Maned sloth brazil
Professor Gastón Giné putting a GPS backpack on a maned sloth


Professor Gaston Giné has been researching maned sloths for over 10 years and much of what we know today about these sloths stems from the results of his work. He is a professor and researcher at the Applied Ecology and Conservation Lab of the Santa Cruz State University’s Biological Sciences department, and a research collaborator of the Instituto Tamandua.

Instituto Tamandua is a Non-Governmental Organization that works directly in the research and conservation of all Xenarthra species in Brazil (sloths, anteaters, and armadillos). Flavia Miranda, the founder and director of Instituto Tamandua, is the deputy chair of the IUCN Anteater, Sloth, and Armadillo Specialist Group.

Together with Professor Gaston Giné, Instituto Tamandua coordinates research into the maned sloths. 


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Flavia Miranda, founder of Instituto Tamandua, working on a Giant Anteater in Brazil. Her research in the past 15 years has been very important for the conservation of sloths, armadillos, and anteaters, including the discovery of 6 new species of silky anteaters!/ Photo: Facebook Instituto Tamandua

Due to the ongoing impacts of the COVID-19 pandemic, funding for wildlife research and conservation has become scarce as government resources are directed elsewhere. This crisis has left maned sloth research and conservation projects in Brazil vulnerable and in danger of running out of resources. 

Thanks to the generous support of our donors, we are happy to have been able to provide funding for 10 new state-of-the-art GPS sloth backpacks that will be used by Gaston Giné and the Instituto Tamandua to continue their important work and better understand the ecological requirements, habitat preference, and movement patterns of this vulnerable species. 


Maned sloth brazil
Professor Gastón Giné releasing a maned sloth with a GPS backpack.

Team Sloth travels to Brazil 

In March 2021, SloCo founder Dr. Rebecca Cliffe travelled to Brazil with two other members of Team Sloth (Cecilia Pamich and Patricio Silfeni), to deliver the new GPS backpacks and learn more about the maned sloths.

They travelled to the Reserva de Sapiranga, near Praia do Forte, where they met up with Gaston, his son Caian, and professional tree climber (and expert sloth spotter) Cosme Guimarães a.k.a. Coy.


maned sloth reserva sapiranga
One of the rangers helping with the radio tracking of maned sloths.


For 7 days the team spent from sunrise until sunset hiking through the reserve searching for the elusive maned sloths. Some sloths were already being monitored by Gaston and needed to have their old backpacks replaced, but a lot of the sloths were new additions to the project.


Maned sloth brazil
It took almost 2 hours to spot this sloth. The signal from his radio collar was strong, but he was impossible to see until he moved into the open.


Every time a sloth was found, Coy would quickly scale the tree and carry the sloth safely down to the ground where important body measurement data would be collected by the team. The new backpack would be fitted, and a brightly colored ribbon would be attached to the back to act as a visual marker for identification.


Maned sloth brazil
This individual was identified as ‘Pablo’ and has a bright yellow ribbon on his backpack.


maned sloths brazil
 Neither the backpack nor the ribbon interfere with the activities of the sloth.

The sloths didn’t need to be anesthetized for the procedure as it was quick and simple, but it was necessary to use special Velcro mittens to cover the fingers and toes to prevent injury to the team.


Maned sloth brazil
Professor Gaston Giné and Dr. Rebecca Cliffe taking measurements. Velcro mittens are being used for safety.


During the course of the week, they managed to put GPS backpacks on 8 maned sloths (and mistakenly tried to capture a lot of termite nests that looked suspiciously like sloths)! 


maned sloth
Sapiranga reserve. The pale green dot was our base, and the yellow dots were the areas where we found the sloths.

Silent Rainforests

During their time in Brazil, the team were eager to learn more about the conservation problems being faced by maned sloths and to see how they could provide more help in the future.  

Having come from Costa Rica (where sloths are literally falling from the trees and climbing through people’s houses), they were shocked to discover how few maned sloths there were inhabiting the Brazilian forest reserves.

The maned sloths they found were also all very shy, hiding at the tops of the tallest trees and moving higher when they heard the sound of approaching humans. This is in stark contrast to the sloths in Costa Rica that tend to ignore people completely and often wander unfearfully into urban areas (and therefore get themselves into trouble). 


Maned sloth brazil


Finally, and perhaps most shockingly, the team were spooked by the eerie silence that followed them through the rainforest reserve where they were working. Upon entering a Costa Rican forest, you will reliably be greeted by the deafening hum of insects, screeching of parrots, and howling of monkeys. The rainforest feels and sounds alive. In the Reserva de Sapiranga of Brazil, the rainforest felt and sounded empty.  


atlantic forest maned sloth brazil
The Atlantic Forest (Mata Atlantica) has suffered the impacts of human development.


At first, they thought this difference was perhaps normal: the Atlantic forests are drier than the wet, humid rainforests of Costa Rica and so biodiversity is understandably different.  But as the week progressed, it became apparent that poaching and human disturbances are big problems in this region. The team stumbled across several different poaching traps, and they noticed platforms that had been erected in trees where poachers would hide. 


Why are maned sloths endangered? 

While it is unlikely that people go out specifically to hunt sloths, it is known that sloths are opportunistically poached for food in some areas (on a recent trip to Guyana we discovered that sloth meat is regularly sold in illegal markets there).

Over time, it seems likely that opportunistic poaching may have contributed to the shy nature and low numbers of maned sloths remaining in the wild. However, this is certainly not the only problem. 


No photo description available.


Maned sloths have a very restricted range – they can only be found in a small strip of forest on the Atlantic coast of Brazil. Over 93% of these Atlantic forests have been lost in recent years due to deforestation for cattle pastures and plantations of sugar cane, cocoa, coffee, and eucalyptus.

maned sloth distribuition
Maned Sloth Distribution / Image: Instituto Tamandua – Ivy Nunes


As a result, maned sloths are severely affected by habitat loss, and the remaining forest reserves where they live are extremely fragmented and isolated. 


maned sloth habitat
The area surrounding the Sapiranga Reserve shows high levels of deforestation.

How to help the maned sloths

In order to safeguard a future for the remaining maned sloth populations, a multifaceted conservation approach that engages and empowers local communities is required. 

An important first step in the development of any conservation strategy is to properly understand the biological and ecological requirements of the species that you are trying to conserve. Without this knowledge, any attempt to mitigate the problems will likely be ineffective and short-lived. 

We are hopeful that the GPS technology that we have provided will help to increase current knowledge about maned sloths, and we look forward to developing further conservation strategies with our partners in Brazil to help maned sloths in the future. 


team sloth brazil
Cecilia Pamich, Cosme Guimarães, Gastón Giné, Rebecca Cliffe, and Patricio Silfeni after a full day of sloth scouting and backpacking.


We would like to say a special thank you to Professor Gastón Giné, Instituto Tamandua, Applied Ecology and Conservation Lab of the Santa Cruz State University’s Biological Sciences department, Prefeitura de Mata de São João, the rangers of Sapiranga Reserve, and all the lovely people that shared their knowledge and experiences with us throughout our trip!


maned sloth team


-Rebecca Cliffe

Founder and Executive Director


How much do sloths sleep?

How much do sloths sleep?

Sloths in the wild only sleep for 8 – 10 hours per day. The myth that sloths sleep all day long has manifested over decades of casual observation and a bad reputation.

Brown and Black Animal on Green Grass
Armadillos – close cousins of sloths – actualy sleep much more than sloths! / Photo: Steve Creek-Pexels

Sloths and sleep: the origin of the myth

The name “sloth” translates as a form of “lazy” in almost every language on our planet. Sloths have been burdened with their bad reputation since they were first described in the scientific literature in 1942 as “the lowest form of existence”.

Before the development of modern animal-tracking technology, scientists trying to understand wild animal behavior had to rely on opportunistic observations. They would simply watch and learn. While this basic approach may work for many species, sloths are unfortunately not one of them.

Sloths are slow-moving, shy, and secretive creatures that are almost impossible to observe for any length of time in the wild. They simply melt into the rainforest canopy and quickly become indistinguishable from the leaves and branches that surround them. They are masters of invisibility.

tales jungle
Photo: Suzi Eszterhas

We now also know that sloths have the same favorite sleeping spots that they will often return to throughout the day and night – interspersed by bouts of activity. A sloth might look like it hasn’t moved from the same place for several days, but it has probably been moving around during the night and has returned back to the same place for a rest. This pattern of behavior has previously tricked curious scientists into believing that sloths can sleep for days on end – something we now know isn’t true at all!

All of this, combined with the myth that sloths are “stoned” because of psychoactive properties in the leaves they eat, has garnered them with an unfair reputation for being lazy.


eating leaves
Three-fingered sloths favor leaves of the Cecropia tree. Dry leaves of Cecropias are smoked as a cannabis substitute due to the apparent psychoactive effects in humans. /Photo: Suzi Eszterhas

The problem of studying sloths in captivity

Due to the difficulties associated with studying sloths in the wild, the vast majority of research into sloth behaviour and sleep has been conducted on captive sloths.

It is becoming increasingly accepted that animal behavior in captivity can not be assumed to be the same for their wild counterparts. For example, in zoos and rescue centers, sloths don’t have to forage for the perfect leaves, worry about behavioral thermoregulation, or remain on high-alert for predators.


Rescued orphan sloth / Photo: Suzi Eszterhas


In addition, without the use of invasive and expensive methods, it is very difficult for an observer to differentiate between ‘sleep’ and ‘rest’. Taking these factors into account, it’s highly likely that the amount of time wild sloths spend sleeping is different from their wild counterparts.


sloth sleep
Photo: Suzi Eszterhas

How we measure sleep in sloths?

Sleep can be accurately measured by using an electroencephalogram (EEG), which records brain activity, and an electromyogram (EMG) which detects electric impulses occurring within muscle tissues.

These devices have been used on wild sloths in the past, but they are extremely invasive and likely disturbed the sloths normal behaviour.

Through our Sloth Backpack Project, we are utilizing the latest in micro-datalogger technology to record every tiny movement in wild sloths – from ascending and descending trees, to chewing and yawning. We are generating data that can be used to determine the sloths’ activity budget in a much less invasive way.

Using our backpack data, and comparing it with historical data collected by the use of EEG and EMG studies, we estimate that wild sloths sleep for 8-10 hours per day.

data loggers science
We use data loggers in the backpacks for the ‘Urban Sloth Project’

What is ‘inactive rest’?

While sloths don’t spend all day sleeping, this does not mean they are active either. They actually spend the majority of their waking hours in something that we like to call ‘active rest’ – they are not sleeping, but they are completely inactive and often have their eyes closed.

Sloths have the lowest metabolic rate of any non-hibernating mammal and the vast majority of their diet is leaf-based. Leaves themselves do not contain many calories, and due to their slow metabolism, the sloth’s caloric requirement per day is also very low (approximately only 100-150 calories per day!).

This means that sloths do not need to spend much time running around looking for food. Instead, they spend as much of the day as they can in an inactive state (which is easily perceived as sleep) in order to conserve energy and avoid detection by predators!


eating leaves
Do you eat salad? – 100g of lettuce contains 13-16 calories!



The true stories behind these famous baby sloth photos

The true stories behind these famous baby sloth photos

With a following rivaling that of the Kardashians, these baby sloths will never know just how famous they have become.

Note: Many of these baby sloths were photographed in rescue centers. SloCo is not a rescue center but we work closely with wildlife rehabilitation organisations on research and education initiatives to further our understanding of these unique creatures.

‘Mira’ – the world’s most famous baby sloth!

This is Miracle, or ‘Mira’ for short- she was found on a forest trail only a few hours old, with her umbilical cord still attached. She was rescued by a passerby and taken to the Sloth Sanctuary of Costa Rica. This photo was taken after she had been cleaned up and given a warm blanket to snuggle into.

You might not recognize this sloth, but scroll down to see her transformation!

Photo: Rebecca Cliffe


This is Mira around 8 months later. This photo was taken by Sloth Sanctuary volunteer Anne Goodall and was first used in the ‘Save Our Sloths’ fundraising campaign 8 years ago. The image went viral and has since appeared on everything, from bumper stickers to billboards.

Unfortunately, this photograph is also one of the most illegally replicated images (did you know that it is against the law to use somebody else’s photograph without their permission? Even if you paint or draw it!) Lots of people and companies sell merchanidse featuring this image without getting Anne’s permission!


Photo: Anne Goodall


Jewel was rescued as a baby with a broken arm by the Sloth Sanctuary of Costa Rica. Her arm was placed in a cast to aid with the healing process (today Jewel still has a bump in her arm where the bones were broken). Jewel and SloCo founder, Dr Rebecca Cliffe, have a close relationship. For a full year, Rebecca monitored every aspect of Jewels life in order to collect data for her PhD (including checking her body temperature every 3 hours for 8 continuous months – day and night)!



Esmeralda & Peanut

Esmerelda and her baby, Peanut, are wild three-fingered sloths living in the rainforests surrounding the Sloth Sanctuary in the South Caribbean. SloCo founder, Rebecca, alongside photographer Suzi Eszterhas, followed Esmerelda and Peanut every day for three weeks. In this well-timed photograph, Peanut is around 2 weeks old and is learning from mom which trees are the best for eating.

Photo: Suzi Eszterhas

Ali & Jessica: the most famous mom and baby!

Ali and Jessica miraculously survived after being hit by a car on Valentine’s Day 2015, with this photo becoming one of Suzi Eszterhas’ most popular pieces. Ali and Jessica are also available for symbolic adoption on our website. To capture this image, Suzi had climbed a tree and accidentally sat on a termite nest. The ants in her pants were worth it though!

Photo: Suzi Eszterhas

Ella, Shilo & Poko

Ella (left), Shilo (middle), and Poko (right) are three orphaned babies who became best friends during rehabilitation at the Sloth Sanctuary of Costa Rica. They would spend all day snuggled up together like this in a bucket in the baby nursery.

Photo: Suzi Eszterhas


Last (but certainly not least), we have Jessica again! In this photo, Jessica is around 5 months old, and her mother, Ali, is estimated to be over 25 years old.

Photo: Suzi Eszterhas

Three-fingered sloth ‘adopts’ a two-fingered sloth baby!

Three-fingered sloth ‘adopts’ a two-fingered sloth baby!

These two sloths are not only different species, but they belong to two completely different families, separated by over 30 million years of evolution. Cross-species adoptions like this are incredibly rare in the wild, with only 3 other documented observations of this happening.

Three-fingered sloth 'adopts' a two-fingered sloth baby
Copyright: Oscar Solano Rojas

What happened?

On the 20th December 2020, Gerald Pereira and Oscar Solano Rojas were guiding a group of tourists in Costa Rica. Sloths are a common sight on these tours, but that day they saw something that they had never seen before – nestled quietly amongst the rainforest canopy they spotted an adult three-fingered female tending to a two-fingered baby sloth.

Gerald and Oscar, both with over 11 years of experience working as ecotourism guides, knew they had witnessed something important.


Three-fingered sloth 'adopts' a two-fingered sloth baby
Copyright: Oscar Solano Rojas

The curious pair were observed in a fragmented strip of rainforest, sandwiched between a river, a pineapple plantation and a busy road. According to Oscar, “in that area, local people take great care of the sloths, so we always go to look there because there is a very large population”.

“Yesterday we started the tour, which we call the ‘Sloth Tour’, as usual. To see them active in the early hours of the day, we started the tour at 6am. Around 8am we arrived at a place where my partner Gerald and I saw a sloth hanging from a Cecropia tree. At first, it did not attract much attention, we saw that she was a female and a baby, but that morning we had already seen 3 baby sloths, and we did not think it was anything special or different from what we had seen. When we paid more attention to them, however, we discovered that it was a three-fingered female and a two-fingered baby.”

Three-fingered sloth 'adopts' a two-fingered sloth baby
Photo credit: Oscar Solano Rojas

“I had already seen the two species in the same tree many times, and at first we thought it was just a coincidence that they were there together. When we found them it seemed like they were waking up. They both started scratching, and then the baby separated from the female, fed on cecropia leaves a little, and I thought that was the end of the interaction.”

“But then you see how the baby returns to the female, and she receives it with total naturalness, that is what surprised us the most. None of us who were there could believe it, neither Gerald nor I, because we had never seen it before. It left me astonished. In rescue centres, I had seen a certain attachment between the two species, but never in their natural habitat, as happened to us yesterday.”

Three-fingered sloth 'adopts' a two-fingered sloth baby
Copyright: Oscar Solano Rojas

As can be seen in the video footage captured by Gerald and Oscar, it does indeed appear that the two sloths interact with the gentle tenderness of a mother-baby relationship. When they returned to the area the next day, they once again found the pair snuggling together in a shady spot in the canopy. It certainly looks like the bond between these two sloths is much more than just a fleeting interaction. It appears as though the female has formally adopted this baby as her own.

Three-fingered sloth 'adopts' a two-fingered sloth baby
Copyright: Oscar Solano Rojas

Odd Alliances

Adult animals adopting unrelated young is nothing new to science, but in most cases these are intraspecies interactions – meaning that they occur between two unrelated individuals of the same species. This has most commonly been observed within sociable species, often herd or pack animals.

Interspecies adoptions – where a female adopts a baby of a different species – is an altogether much rarer occurrence in the wild. In fact, there have only ever been 3 other documented instances of this happening, and it has never before been observed in sloths. 

In 2004, a group of capuchin monkeys were documented caring for a baby marmoset, and in 2014 a bottlenose dolphin adopted a baby melon-headed whale and nurtured it for it for 3 years. More recently, a lioness in India was found to have adopted an orphaned leopard cub in 2018 and she raised it alongside her own offspring.

Why do cross-species adoptions occur?

In evolutionary terms, caring for another animal’s offspring like this doesn’t make much sense. Raising a baby demands a lot of time and energy (something which a sloth has a limited supply of), and it is usually done with the purpose of propagating an individual’s own genes. So why do cross-species adoptions like this sometimes happen?

The truth is, scientists are still trying to understand it. Because these events are so rare, there isn’t much information available and each observed case appears to be very different. There are two popular theories:

  1. Instinct: A lot of adult female animals are biologically hardwired through evolution to care for helpless infants. A cross-species adoption might occur accidentally after a female has recently given birth herself, when high levels of the hormone oxytocin encourage her to bond with the orphaned baby (even if it isn’t hers!).
  • Mutual benefit: If the benefits of the raising an unrelated baby outweigh the costs, this could explain why some interspecies adoptions take place. For example, it could be beneficial for a group of animals to add a new individual that would help to secure more food, or provide added protection. In some social species the simple benefit of companionship may be a driving force! This is unlikely to be an important factor for our solitary sloths though.


Lioness, Nosikitok, nurses a leopard cub in the Ngorongoro conservation area in Tanzania
Lioness, Nosikitok, nurses a leopard cub in the Ngorongoro conservation area in Tanzania. Photograph: Joop van der Linde/AP

How did this happen?

The circumstances surrounding this adoption are not entirely clear, but SloCo founder and sloth expert Dr. Rebecca Cliffe has some ideas about what might have led to this unusual event.

“This is the first time that anything like this has ever been seen before in wild sloths, and it is certainly very interesting. I am used to sloths surprising us, but this has to be one of the most unusual things I have heard about. I suspect there are three possible scenarios which may have led to this happening:

1) Accidental human interference. Maybe someone found the baby sloth alone and tried to ‘reunite’ it with its mother, but accidentally paired it with the wrong sloth. Reuniting baby sloths with their mothers is a surprisingly common requirement for people in Costa Rica as babies are often found alone on the ground after falling from the tree.

A lot of people don’t realise that there are two very different types of sloth, and so they might not have realised what they were doing. In this situation, however, I would expect the adult sloth to reject the baby and so this feels like an unlikely scenario

Three-fingered sloth 'adopts' a two-fingered sloth baby!
Copyright: Oscar Solano Rojas

2) The baby sloth lost it’s own mother, and instinctively clung onto the fur of another sloth. Baby sloths are born with a strong instinct to cling onto mom’s fur, and if they are separated, they tend to cling onto the next best thing. It isn’t impossible to think that this baby may have climbed onto the three-fingered sloth after becoming orphaned. However, in this situation I would also expect to see the adult sloth looking agitated and stressed out by her new uninvited companion – and I doubt the relationship would last more than a few hours.

Three-fingered sloth 'adopts' a two-fingered sloth baby!
Copyright: Oscar Solano Rojas


3) The baby sloth lost its own mother, and the adult sloth recently lost a baby of her own. This unusual combination of events would provide a feasible opportunity for the pair to bond naturally due to a mixture of instincts and hormones. Although extremely rare, I think this is probably the most likely scenario!”


Three-fingered sloth 'adopts' a two-fingered sloth baby!
Copyright: Oscar Solano Rojas


What happens next?

This unprecedented behavior leaves all of us with many questions – particularly regarding the welfare of both sloths! Will the baby survive? It’s certainly possible. While they are different species, they do share a broadly similar ecology.

The diets of both sloths overlap heavily, with both being predominantly folivorous (eating only leaves). Two-fingered sloths tend to be more flexible and adaptive with their choices, while three-fingered sloths are more selective about what types of leaf they will eat. With both species, babies maternally inherit knowledge about which trees are safe to feed from – and this arrangement may work in the baby’s favor!

Three-fingered sloth 'adopts' a two-fingered sloth baby!
Copyright: Oscar Solano Rojas

Furthermore, it appears as though the baby sloth is approximately 7 months old. At this age, the baby would not be as reliant upon a steady source of milk from the mother as the natural weaning process would be taking place. Although the adult female could be producing milk, we don’t think this is essential for the survival of the baby at this stage.

Two-fingered sloths are also much larger than their three-fingered counterparts when fully grown, which means that the adoptive mother may have a challenge on her hands when lugging around her overgrown offspring.

Three-fingered sloth 'adopts' a two-fingered sloth baby!
Copyright: Oscar Solano Rojas

But what happened to the baby’s biological mother? This remains a mystery. Considering the location in which the pair were observed is highly disturbed, it may be that she got into trouble with the busy road or nearby pineapple plantation. Or perhaps there was an accidental baby mix-up, and somewhere in the rainforest, a mother two-fingered sloth is tenderly nurturing a baby three-fingered sloth. It’s doubtful we will ever know for sure.

While there are certainly a lot of challenges for this pair to overcome, here at SloCo we have high hopes for their survival. After the unprecedented global difficulties that 2020 has brought, we are happy to embrace this heart-warming story (which has all the makings of a future Disney movie!).



We will be working closely with both Gerald and Oscar to monitor the two sloths as time goes on – we will keep you updated on their progress! For now, we are keeping our fingers and toes crossed for a happy ending.

2021 Update:

It’s with a heavy heart that we must inform our supporters that the wild three-fingered sloth mom that was found to be caring for a two-fingered baby has passed away.

Local guides who were tracking the pair witnessed the mom and baby fall from their tree. Unfortunately, mom did not survive the fall. The baby was uninjured and climbed back up into the tree.

The guides continued to watch over the baby for the rest of the evening, and returned to the spot every day to check on him – but after three days he had ventured off on his own into the rainforest.

We estimate that the baby was around 8 months old, at which point he would naturally begin to distance himself from his mom. Team Sloth is optimistic that his two brilliant sloth moms taught him everything that he needs to know in order to survive in the wild!


-Sloth Team


The ‘mummified’ skin of a giant sloth proves that they coexisted with the first humans of South America

The ‘mummified’ skin of a giant sloth proves that they coexisted with the first humans of South America

Although it was on display for a long time at the Museum of La Plata, Argentina, its age was uncertain. A new study indicates that giant ground sloths lived 13,000 years ago and coexisted with the first humans of South America.

The mummified skin of the mylodon was found on a scientific expedition organized in 1899 by the Museo de La Plata (UNLP). Mylodons were an extinct genus of animals that lived during the Pleistocene, a period that ranged from approximately 2.5 million to 10 thousand years ago.

Since it was first discovered in 1899, it has remained on exhibit. The artifact is a true treasure considering its surprising degree of preservation: it still has hairs and soft parts. After extensive discussions about its age, this remarkably preserved skin lost the interest of paleontologists until recently when a group of experts resumed studying it and dated it again. This time they used sophisticated techniques that left no room for doubt: the owner of that tissue lived about 13,200 years ago. This discovery has just been published in the journal Quaternary Science Reviews.

Secretos de una joya del Museo de La Plata: científicos del CONI
Leandro Pérez, one of the researchers, next to the showcase where the skin is exhibited. Photo: courtesy of researchers.

The skin of the giant sloth

The giant sloth – the common name for this genus – was one of the largest land animals in South America, weighing more than 1 ton and measuring 3 meters (almost 10 feet) in length. It had huge claws and walked on all fours, although it is thought that it could also stand on its hind feet (bipedal). With its herbivorous habits, it was part of the South American megafauna, the large mammals that dominated the planet during the Pleistocene.

The skin was found in the Cueva del Milodon (Milodon’s cave), a natural formation located in southern Chile that was explored in the late 19th century. The cave contains countless paleontological remains, and even evidence of early human activity. At that time the geographic limits of Argentina were still being established, which allowed for expeditions of many different origins to go and collect materials. As the story goes, when Argentinian naturalist Florentino Ameghino first saw the remains, he assumed that they belonged to a living species. This led him on an impassioned quest to find a living specimen, which of course did not happen.

giant sloth skin
Photo: Courtesy researchers

“The skin is really striking: it is a centimeter and a half thick with long reddish-yellow hairs and it is hard like wood. In what would be the interior, it is covered by a ton of small bones, similar to a suit of armor, which is typical of some species of fossilized sloths,” explains Néstor Toledo, CONICET (National Council for Scientific and Technical Research) researcher on the Faculty of Natural Sciences and Museum of the National University of La Plata (FCNyM, UNLP) and one of the authors of the work.

The scientific process

First dated in 1974 with questionable results, the team of scientists sent a sample back to the same radiocarbon laboratory in the United States that had done the original analysis. They used a method to determine the age of carbon-containing materials and this time it was clear that that the sample was over 13,000 years old. The authors of the study also sent a fragment of skull bone from the same cave to an Argentinian laboratory which turned out to be 11,300 years old. This was the same age of two bone tools carved by ancient humans that were found next to the sloth hide, according to the original reports of the find.

The specialists also examined two sloth shoulder blades, one belonging to the local collection and the other belonging to the Zurich Museum of Natural Sciences. These bone pieces, which were dated between 12 and 13 thousand years old, have cut marks on made by tools and evidence of them being dragged across the ground. “This constitutes indirect evidence of human presence, that of course must continue to be studied, but it is an indisputable proof of coexistence with human beings and, if verified, it would be one of the oldest records in South America,” says Leandro M. Pérez, CONICET researcher at the FCNyM and leading author of the publication. This question takes on a special interest considering the debate on whether or not this giant fauna coexisted with these first settlers.

giant sloth skin
Photo: Courtesy researchers

In addition to the new ages obtained, the investigation includes an exhaustive review of  the dating methods of all the mylodon remains found in that same cave which appear in the scientific literature. Starting with the first of them, carried out in 1951 by Williard Libby, the winner of the Nobel Prize in Chemistry in 1960 and creator of the radiocarbon method, they verified a total of 36 records, discarding those that were unsuccessful or uncertain.

“We have taken on the monumental job of searching for each published piece of information, tracking the sample it refers to, and calling the laboratory in charge of dating it to trace a match between these references. We found some errors and we left only those reliable historical values,” ​​Pérez explains, and adds:” It is not that before they worked badly, but that the protocols that we use today did not exist at the time. For example, they didn’t understand the importance of including a photo or a drawing of a material or assigning it a catalog number in the collection.

Interesting questions

As a final reflection, the researchers highlighted two important values ​​of their work. “On the one hand, there is interest on the climatological level, since it was a time of intermittent glaciations. Despite the very harsh conditions due to the cold and the amount of ice, this cave was inhabited continuously for at least a thousand years, according to our bibliographic review. For this reason, it raises countless questions about how this fauna could have evolved, which in the case of the ancient sloths were gigantic and woolly, while their current relatives are small and live hanging from the trees in tropical jungles,” argues Toledo.

Secretos de una joya del Museo de La Plata: científicos del CONI

Pérez alluded to a second relevant question, related to “the importance of valuing the heritage we have and the way the naturalists worked at that time, people who traveled to distant and hostile places without even knowing if they would return alive. Many museums in the world have pieces from this site because they were bought from collectors. But on the other hand, very few, like ours, have materials recovered in scientific expeditions organized and led by researchers from the institution.”

carlos ameghino
Fiorentino Ameghino, considered the first Argentinian paleontologist, and team in one of their expeditions.

Mummification: yes or no?

Although there is talk of “mummified” skin, in reality it is unclear if the term exactly applies to the way the famous “sloth leather” was preserved. “It is not how one might imagine an Inca or Egyptian mummy, subjected to a series of deliberate treatments to preserve it in this way. There was no dehydration here because the cave was terribly cold and humid, and it wasn’t from freezing either.

What took place was a more complex process. Right now we are carrying out a chemical analysis on some of the microcrystal sheaths that cover each hair, that we saw through electron microscopy,” described the authors, who speak of a kind of “natural tanning.” The material was buried under a meter-thick layer of manure that was compacted, and therefore lacked oxygen. “We think that the excrement produced the release of tannins, chemical compounds that are used to tan leather, and that spontaneously triggered the process,” concluded the experts.


-By Mercedes Benialgo, CONICET La Plata

Leandro M.Pérez, Néstor Toledo, Florencia Mari, Ignacio Echeverría, Eduardo P. Tonni, Marcelo J.Toledo. Quaternary Science Reviews. Radiocarbon dates of fossil record assigned to mylodontids (Xenarthra – Folivora) found in Cueva del Milodón, Chile. DOI:


Love avocados? Thank the giant ground sloths!

Love avocados? Thank the giant ground sloths!

Did you know that we can thank giant ground sloths for the avocados we have today? Giant ground sloths were one of the few ancient herbivores large enough to swallow avocados whole, thus serving as an important seed disperser for these delicious fruits that we know and love today!

Illustration of the giant ground sloths by Robert Bruce Horsfall/Source: Wikimedia Commons


Many plants, especially in tropical ecosystems, have evolved to rely upon animals to spread their seeds. Only extra-large herbivores such as the giant ground sloths had the ability to swallow avocado seeds whole, meaning that they could carry them around in their digestive tracts and eventually defecate them far away from the parent tree!

Evidence of these ancient symbiotic (mutualistic) relationships can still be seen today. For example, honey locust trees (Gleditsia triacanthos) have large sweet-smelling seed pods that were eaten by megafauna. They also have big, intimidating spikes on their trunks which likely served as an important defense against these giant herbivores. Now a popular city tree due to their ability to withstand poor conditions, modern versions of honey locust trees have been bred without spikes although their supersized seed pods still litter our bustling city streets.

Seed pods and thorns of the honey locust tree (Gleditsia triacanthos). Although seemingly powerless against modern tree dwellers these spikes likely served as vital protection against the large herbivores of the Pleistocene./Images:

How big were the giant ground sloths?

These ancient ancestors of modern-day sloths truly lived up their name. Like bears and anteaters, they had the ability to stand on their hind legs, making them the largest bipedal mammals to have existed. Over 100 species of giant ground sloths lived throughout North, Central and South America, ranging in size from the formidable Megatherium americanum which towered 3.5 metres tall (12 feet), and weighed up to 4 tons, to the considerably smaller 90-kg (200-lb) Cuban Megalocnus. 


Skeleton of the giant ground sloth (Megatherium americanum)/Source: Wikimedia commons


The giant ground sloths of North America disappeared around 11,000 years ago and their South American cousins followed suit around 10,200 years ago. However, amazing fossil evidence from 2007 revealed that 200-lb Megalocnus were still lumbering around the islands of Cuba as little as 4,200 years ago!


Skeleton of the considerably smaller Cuban ground sloth (Megalocnus rodens)./Source: Wikimedia Commons

Why did the giant ground sloths disappear?

Like many of the memorable megafauna of the last ice age, the exact cause of their extinction remains somewhat murky. Megatherium fossils have been found with cut marks on them, suggesting that ancient humans did consume these giant beasts. However, humans and the giant ground sloths of Cuba coexisted for a period of about 1,000 years. It is likely that a combination of over-hunting and/or climate change led to their demise.


Artist’s interpretation of the giant ground sloth (Megatherium) of the Pleistocene and two Glyptodon./Source: Wikimedia commons


Although the last of the giant ground sloths disappeared around 4,200 years ago, modern sloths carry on their legacy. Scientists have hypothesized that modern-day two and three-fingered sloths evolved from two distinct lineages of extinct giant ground sloths. In other words, although not closely related, two and three-fingered sloths both evolved independently to live in trees, in a process called convergent evolution. However, recent genetic evidence suggests that the species of sloths alive today may have evolved from an ancestor that was comfortable on the ground as well as in the trees.


The future of avocados

Without their ancient seed dispersers, the future of avocados is now in our hands. Unfortunately, avocado trees are quite sensitive to changes in temperature and water. A single avocado requires 60 gallons of water to grow. Fluctuations in rainfall and temperature due to climate change are causing shortages of these lucrative crops. Moreover, the expansion of avocado farms in Mexico has led to the destruction of pine and fur forests thus affecting monarch butterflies. The high demand for avocados has even caused gang warfare to break out in areas such as the Michoacán state of Mexico, where almost 80% of the US’s avocados come from.

Also known as “alligator pears” avocados became popular due to the targeted marketing efforts of Californian farmers in the 1990s./Image:

A sustainable future for avocados, means growing them in places where water is plentiful using agricultural methods (such as agroforestry) that make space for biodiversity.


-Katra Laidlaw



Five-ton giant sloth lived in Costa Rica seven million years ago!

Five-ton giant sloth lived in Costa Rica seven million years ago!

A giant sloth weighing five tons and whose height could exceed twice that of a human being was part of prehistoric Costa Rica seven million years ago.

A group of paleontologists is working hard to determine the characteristics of this giant sloth to see if it corresponds with previously described species – or whether it is completely new to science!

This is part of a project that started in 2003 in San Gerardo de Limoncito, Coto Brus, about 11 kilometers from San Vito. In this area, the researchers searched for bones and fossils of different species.

For more than a decade, Ana Lucía Valerio, coordinator of Geology at the National Museum, and César Laurito from the National Institute of Learning (INA) searched and analyzed more than 2,600 samples of bones from dozens of different species that appeared throughout the expeditions.

giant sloth
The bones found correspond to giant sloths similar to those in this image, whose height can easily exceed twice that of a person. Illustration: Franklin Rodríguez

“When I decided to go for paleontology, no one cared for something to appear here. Venturing out to find mammals was unthinkable. They told us ‘you are looking for little bones, it is not important’, but the finding makes the world look again and say ‘something is happening here, something we did not expect and that is changing the vision of biological exchange'” Laurito explained.

This region is important because it provides further proof that Central America served as a bridge for animals to cross from South America to North America and vice versa. 

“We are talking about something very old. The Isthmus only closed about 3.5 million years ago, but these sloths lived seven million years ago. So how did these giant animals from South America get to southern Costa Rica if they had no adaptations for swimming? It is possible that for a time there was a pass, a land bridge, for these animals to cross. This passage could exist for a short period of time, but for paleontology, a short period of time could be a million years ”

“In other words, species from South America are appearing much earlier than expected – by about four million years” he clarified.

Describing the sloths:

In recent years, Valerio and Laurito have described many different species of prehistoric horses, camels, armadillos, and other types of mammals on Costa Rican soil.

However, they had a problem with the sloths’ material as they had no way to compare it. This type of research in paleontology is very new in Costa Rica, and so they formed a collaboration with Ascanio Rincón, head of Paleontology at the Venezuelan Institute of Scientific Research, who has been studying these prehistoric giants for many years.

Rincón helped to complete the next part of the analysis: determining what kind of sloths they are. All of the bones were found at the same site, but they accumulated during different years of searching.

“There is no record of these animals in North America until much later. What prevented them from crossing? Or what did they find here that made them stay longer without moving?” Rincón wonders.

For this new analysis, all bones must be photographed, measured, analyzed, described and compared with the bones of other giant sloths. After all of this, important aspects of these populations can be determined.

giant sloth found in costa rica
The Venezuelan paleontologist Ascanio Rincón (left) is in the country to collaborate with the research of Ana Lucía Valerio Zamora and César Laurito Mora, who have spent years studying the paleontology of fossils found in Coto Brus. In the photograph they present the ankle bone of a giant sloth. Photo: Rafael Pacheco

“Now we have to do the hard work, which is to compare it with the rest of the 14 or 15 genera that exist and determine who it resembles the most and who it resembles the least and see if we are dealing with a new species,” said Rincón.
This is not easy. It is very difficult to find complete bones and so they only have small samples from which to draw conclusions.

“This is not how it looks in the movies. Not that it was just brushed off a bit and there it all appeared. We had to chop very hard rocks to be able to remove this. It took a lot of strength, a lot of searching, and sometimes bones of some species appeared, while sometimes other bones of other species. What we have today was put together and gathered over several years ”, Laurito indicated.

Rincón added: “It is hard to be able to know what is happening with only 15% of the body; how to put this puzzle together? In this case, we do have material from various types of bone that help us to better understand the panorama”.

The researchers reported that at least three individual sloths have been found as they discovered three bones of the same type but different sizes (ages). This indicates that these giant sloths may have traveled in a herd or as a family.


giant sloth
These are some of the giant sloth bones scientists are analyzing. Photo: Rafael Pacheco

What do we know about this animal?

Although it is difficult to properly visualize what these extinct sloths looked like, scientists do have some ideas!

For example, it is known that they walked on the soles of their back feet and on the knuckles of their hands. The front claws were very strong and were probably used for digging. Furthermore, due to their massive size and weight, these sloths probably did not climb trees!

Their teeth were so strong they could feed on wood and other hard materials. These teeth had a remarkable ability to regenerate from the wear and tear that was incurred when chewing. In fact, chewing was essential to prevent the teeth from overgrowing and causing problems!

Giant sloths are known to have been social animals, possibly living in large herds or family groups.


Giant Ground Sloths lived in North and South America and went ...

The importance of the discovery

Within these discoveries there could be now-extinct species that are new to science.

“The fossil hunter does not kill his prey, he resurrects it. We resuscitate that dam that we are looking for in order to get to know it and for people to know it” said Rincón.

Why is this important? Rincón was emphatic: “This type of knowledge helps us to understand who we are, where we came from, and it gives identity to the Isthmus. We cannot judge a book by its last page, we must see what comes before, and that is why it is necessary to study paleontology ”.

-Source: Diario La nación Costa Rica

With a little help from my friends: sloth hair, moths and algae

With a little help from my friends: sloth hair, moths, and algae

Sloths are naturally solitary animals, but they are not all alone up there in the canopy. In fact, sloths have an entire ecosystem living in their fur made up of different species of algae, fungi, moths and insects. That’s millions of organisms for company!

Sloth hairs have a unique structure that involves microcracks. These microcracks create the perfect environment for algae and fungi to thrive.

sloth hair friend
Three-fingered sloth hair under a microscope! You can see the microcracks and green algae. 

The microorganisms living in these cracks were investigated by biologists for the first time in 2014, and they discovered species of algae and fungi which have not been found anywhere else in the world!

These fungal species are currently being investigated by microbiologists, parasitologists, and oncologists alike, as some strains are showing uses in treatment for malaria, chagas disease, and even breast cancer.

sloth friend algae
Different strains of green algae found in sloth hair.


Good friends that provide camouflage against visual predators

Sloths have a mutualistic ectosymbiotic relationship with the ecosystem growing on their backs. The fungi, algae, and moths greatly benefit from this relationship as they have a habitat to thrive in. The sloth benefits because these organisms are key to the sloth’s best defense against predation – camouflage.

Hunters that use their sense of sight, such as raptors, will often bypass sloths when searching for prey because the growth of algae and fungi give the sloth’s fur a green tinge, allowing them to blend into the rainforest canopy. This, along with the sloth’s slow movement and other creepy crawlies that make their home in the sloth’s fur, means that sloths usually go undetected by predators who hunt by sight.

sloth selfie distance
Sloths blend in perfectly with the trees they live in.

Sloths smell like the jungle

But what about the predators that hunt by scent? Sloths don’t produce any body odor at all! The growth of this ecosystem in their fur means that sloths look like the trees, they smell like the trees and they even move like the trees (very slowly). 

sloth moths
Sloths look and smell just like the jungle that surrounds them. / Photo: Suzi Eszterhas

Sloth moths

Sloth fur is also the perfect home for six different species of sloth mothsBradypodicola hahneli, Cryptoses choloepi, Cryptoses waagi, Cryproses rufipictus, and Bradypophila garbei.

These moths are exclusively found living in sloth fur and can coexist together on the same sloth. Studies have shown that generally, the three-fingered sloth carries more moths than a two-fingered sloth, with one study recording more than 120 moths in a three-fingered sloth’s fur.

sloth friend moths
Sloth moths are unique to sloth fur! /Photo: Suzi: Eszterhas

When the sloth descends from the canopy once a week to go to the toilet, the moths will crawl from the sloth’s fur onto the fresh sloth poop to lay their eggs. This is the ideal place for these eggs to hatch, as the larvae are coprophagal which means they feed on the sloth poop. Once the larvae develop into moths, they will fly up into the trees to find an appropriate sloth to call home. And thus, the cycle begins again.

Without the sloth, these moths could not exist. The sloth gives these creatures a home and provides them with food – moths have a proboscis rather than a jaw, which they use to suck up the moisture from the sloth’s eyes and secretions from the sloth’s skin.

poop sloth moths
A sloth will only poop on the ground – a ritual that sloth moths have taken advantage of! 

The circle of life!

Sloth moths can sometimes also attract unexpected visitors. Recent footage has emerged from Cahuita National Park, Costa Rica, showing a juvenile Capuchin monkey picking and eating the moths from the fur of a two-fingered sloth! 

This incredible sight had never been captured on film before, and it is not a behaviour that we were aware of! How often does this happen in the canopy while no humans are around to watch? Something similar has also been observed with a brown jay picking the moths from the fur of a three-fingered sloth!

So, if you ever see a green sloth covered in moths, know that that is a very healthy sloth with lots of ‘creepy crawlie’ friends!

Sloth Genetics: a surprising twist

Sloth Genetics: a surprising twist

Six years ago, SloCo Founder Dr. Rebecca Cliffe launched a major research project into sloth genetics in Costa Rica. She started this project because she was concerned with the number of wild sloths in the South Caribbean region that are being born with debilitating birth-defects (missing fingers/toes, malformed ears, and misshapen limbs), and she wanted to know what was happening.

The results of this project have now been published and they reveal an unexpected situation with far-reaching implications for future sloth conservation and rescue efforts.

Cover image created by Dr. Chloe Robinson 
sloth genetics hair sample
Dr. Rebecca Cliffe, a sloth biologist, collecting hair samples from an anesthetized three-fingered sloth for a similar genetic study. Photo by Suzi Eszterhas


In order to find out what is really going on, we collaborated with Dr. Chloe Robinson, Swansea University and the Sloth Sanctuary of Costa Rica to undertake the first exploratory investigation into sloth population genetics in Costa Rica.

We collected hair samples from 98 two-fingered sloths (Choloepus hoffmanni) that originated from different regions throughout Costa Rica and used microsatellite analysis to look at the population genetics.

Infographic by Dr. Chloe Robinson


We made 3 important discoveries regarding sloth genetics:

Finally, after many years of hard work, we are delighted to announce that the results of this research have now been published as an open-access article in Evolutionary Applications. We have summarized the results below.

We were able to identify 4 genetic groups of two-fingered sloths in Costa Rica (this is similar to having 4 genetic origins). If you are familiar with Costa Rican geography, these are the groups that we identified:

  • The West – sloths from the San Jose region
  • The North – includes sloths from areas surrounding Guápiles and further North
  • The East – sloths from within Limón city and surrounding areas
  • The South East – the South Caribbean region ranging from Bananito down to Manzanillo and BriBri.


sloth genetics costa rica


It is important to note that there are probably many more groups than the four that we identified, but for logistical reasons we could not collect samples from sloths spanning the whole country. Our results only reflect the areas where we were able to focus our sampling efforts.

1) Sloths in the North are genetically distinct.

Sloths in the ‘North’ group were found to be genetically very distinct when compared to the other populations. This means that sloths in this region are substantially different from sloths in other areas of Costa Rica that we sampled. We suggest that it may be important to recognize this sub-population as a separate unit for management and conservation purposes.

A distinct sub-population like this is sometimes referred to as an Evolutionarily Significant Unit (ESU).


Figure taken from the publication. Terrain map of sample sites in Costa Rica where 98 individual Choloepus hoffmanni sloths were hair sampled for genetic analyses.


2) Sloths in highly urbanized areas are inbreeding.

Sloths in the ‘West’ group have higher levels of inbreeding, (when individuals who are closely related reproduce). This may not be surprising when we consider that sloths here are restricted to living in severely fragmented forest pockets within the highly urbanized San Jose region.

This suggests that we need to focus more conservation and research efforts in this region to better understand the long‐term effects of habitat fragmentation.

sloth genetic deformities
This baby sloth was born with just one digit on each limb. The survival rate of individuals like this is very low.

3) Sloths have been moved around by humans.

Finally (and perhaps most importantly), we discovered that sloths in the West, East and South East groups were all surprisingly similar. This close relatedness between sloths living on opposite sides of Costa Rica is an unexpected and potentially concerning result. Particularly when we consider the vast geographical distance between these populations and the inability of sloths to travel long distances.

Interestingly, sloth populations in the South Caribbean were found to be more genetically diverse and had high levels of admixture (which means lots of sloths from lots of different origins have been reproducing with one another).

All of this points towards the translocation of sloths by humans in Costa Rica, where individuals have been removed from their areas of origin and released somewhere else.


sloth genetics costa rica

How could this happen?

When we consider that approximately 3 – 4 sloths are admitted into rescue centers every single day in the South Caribbean, it is not surprising that some of these animals may have originated from further away.

The translocation of wildlife was particularly prevalent in earlier years when there were not as many rescue centers who knew how to properly care for sloths. The government of Costa Rica (and in one case a national airline) would regularly deliver inured sloths from all over the country to the Sloth Sanctuary on the Caribbean Coast as they were considered to be the only experts in sloth rehabilitation at the time.

This has since changed. In the last decade there has been an explosion of new rescue centers. Costa Rica now has more rescue centers per square mile than any other country, with over 250 registered facilities currently rescuing and rehabilitating wildlife! The current abundance of rescue centers means that the cross-country translocation of sloths may be less of a problem, but the regulation of release protocols is more difficult.


Is this mix-up of sloth genetics a bad thing?

We do not know, but it could be.

You may think that high levels of genetic diversity are considered to be a good thing in wildlife conservation – and this is true. Increased genetic diversity means less inbreeding has occurred and gives populations a stronger ability to adapt when faced with change.

However, as with most things, it is rarely that simple. Mixing individuals from different genetic backgrounds can also have a dangerous effect on the health and viability of populations through a process called ‘outbreeding depression’.

loss of local adaptations


Animals often have unique genetic adaptations that help them to survive in the particular environment in which they live. For example, sloths that live in cold montane regions have adaptations to cope with a colder climate, including longer, thicker, and darker hair compared to their lowland counterparts. By moving individuals around, these adaptations can be lost and the inter-breeding that occurs can negatively impact the health of these populations.

A similar situation was recently discovered in orangutans that were reintroduced to the wild from rescue facilities in Borneo without knowledge on the genetic background and subspecies status of the individuals.

In line with this, there is an emerging global awareness of the need to consider the genotypes of animals prior to release, including official guidelines and recommendations set out by the International Union for the Conservation of Nature. However, in Costa Rica, there are currently no existing protocols or legislation to encourage or regulate this practice.

Sloths living in lowland tropical rainforests have different features compared to sloths of the same species that live in mountainous regions / Photos: Suzi Eszterhas

What does all of this mean for sloth conservation?

The genetic diversity between separate sloth populations have emerged over the course of millions of years. By mixing together populations that perhaps haven’t been in contact for millennia, we are potentially causing irreparable changes.

It may be that inter-breeding sloths from different genetic origins has no negative effects at all. But what if it does? Suddenly, we will have inadvertently compromised the viability of wild sloth populations and no amount of conservation work can ever reverse that damage. 

Is it worth the risk?

This discovery means that rescue facilities in Costa Rica should consider the genetic background of rehabilitated sloths when planning future reintroductions. Sloths should be released in the areas where they originated from whenever possible.

This will undoubtedly present a challenge for overburdened and underfunded rescue centers. Combined with increasing pressure for post-release monitoring, it may seem impossible for animals to be returned to the place of origin and simultaneously tracked to ensure survival.

Furthermore, it may not be possible to always return an animal to the place that it came from. There may be a lack of suitable habitat in that area, or the rescue center may not have accurate records on where the animal was originally found (rescued animals often pass through several pairs of hands before arriving at a rescue facility, and tracking down the origin can sometimes be difficult).


What can we do moving forward?

There will be no convenient solution, but we must work together to find one.

Ultimately it is going to require increased government assistance, funding and collaboration between different rescue centers and release sites throughout Costa Rica. It will require increased transparency and improved record keeping in order to ensure that rescued sloths are returned to where they were found. 

Furthermore, it will require the preservation of habitat where these distinct sloth populations are living (since they cannot be brought elsewhere).

When sloths were first being transported around the country, we didn’t know better. Now we do. Equipped with this new knowledge, we can now ensure that our actions to help them will truly lead to a long and healthy future for sloth populations in Costa Rica.


sloth genetics


~ Dr. Rebecca Cliffe

Founder and Executive Director