Prehistoric Rock Art Might be Early Representations of Giant Ground Sloths 

Prehistoric Rock Art Might be Early Representations of Giant Ground Sloths

In the Amazon rainforests in the country of Colombia, there is a place called Serranía La Lindosa, with rock cliffs decorated in ancient drawings. There are thousands of paintings covering 12 kilometers (8 miles) of rock in an area that has been largely inaccessible. Some of the paintings depict animals easily recognizable to modern people, such as turtles, guanacos, or humans—and just possibly, giant sloths.


Juancho Torres/Anadolu Agency via Getty Images


A study by José Iriarte and his colleagues published in the journal Philosophical Transactions of the Royal Society proposes the following:

“We argue that they are Ice Age rock art based on the (i) naturalistic appearance and diagnostic morphological features of the animal images, (ii) late Pleistocene archaeological dates from La Lindosa confirming the contemporaneity of humans and megafauna, (iii) recovery of ochre pigments in late Pleistocene archaeological strata, (iv) the presence of most megafauna identified in the region during the late Pleistocene as attested by archaeological and palaeontological records, and (v) widespread depiction of extinct megafauna in rock art across the Americas.”

Daily life scenes

The paintings of the Serranía de la Lindosa are surprisingly well preserved. Some of the scenes seem to show the first contemporary humans in early Amazonia going about their daily life, while others seemingly depict ritual scenes, hunting, interacting with plants, and forest and savannah animals.


Photo: Wikipedia / Julianruizp


Pictures of birds, turtles, and other animal species that inhabit this large tropical forest require little interpretation; however, there is controversy among paleontologists and archaeologists about whether the other creatures represented are in fact giant sloths, elephants, and prehistoric horses.

A giant sloth with a baby?

One of the pictures is the silhouette of a large animal that might be a giant ground sloth, along with a miniature version of itself that it is probably safe to call its offspring. As any would-be artist of modern sloths can tell you, they are not creatures with particularly distinctive shapes.


Ice Age megafauna rock art in the Colombian Amazon? José Iriarte, Michael J. Ziegler, Alan K. Outram, Mark Robinson, Patrick Roberts, Francisco J. Aceituno, Gaspar Morcote-Ríos and T. Michael Keesey


Interpretation of the silhouette as a sloth relies heavily on the assumption that the ancient artists faithfully represented the proportions of the creature in question, which—given the depictions of the nearby human figures—they did not always do.


(a) Giant sloth painting at La Lindosa: 1. massive claws; 2. short rostrum; 3. large head; 4. robust thorax; 5. inverted pes; 6. offspring; 7. miniature men. (b) Artistic reconstruction of Eremotherium patterned after its closest living relative Bradypus. (c) Artistic reconstruction of Arctotherium patterned after its closest living relative, Tremarctos ornatus (Mike Keesey). Keesey’s reconstructions are figurative works of art, where he took the liberty of adding features that are not visible in the rock art like fur, ear canals and wrinkles, among other features. (Online version in color.).


“ Its overall morphology, large head, short rostrum, robust thorax, reduced number of digits on the pes, and prominent claws recall a giant ground sloth. Presented in a quadrupedal stance, the sizable forearms appear to be longer than the hindlimbs. The manus consists of three to four digits extended distally, whereas the pes appears to have five digits with varied orientations.

Notably, the depicted animal appears to exhibit pedolaterality, that is, the characteristic inverted pes, where the dorsal surface of the foot faces laterally and the planar surface of the foot faces medially. Three transversal lines compartmentalize the body in four parts and give the figure an appearance of surficial texture.

The white mark on its head seems to be representing an eye. Behind the head, there appear to be a few protuberances along the dorsal surface that might represent prominent scapula and shoulder musculature. The animal is accompanied by an offspring and surrounded by animated miniature men, some of whom extend their arms towards the painting.

The relationship of the animal with the men appears to be central to the artist’s message. The comparatively smaller illustrated humans that accompany the animal appear to provide a perspective on a scale that points to the sheer size of the specimen.”


The controversy

Interpreting ancient rock art is a much more difficult process than it initially seems. For example, how old is “ancient”? The art on the cliffs of Serranía La Lindosa is made with mineral pigments that are not suitable for carbon dating, so inferences must be drawn from organic materials in the area that CAN be carbon dated, such as bone tools that might have been paintbrushes, or food remains from the human settlements nearby.


Ice Age megafauna rock art in the Colombian Amazon?
José Iriarte, Michael J. Ziegler, Alan K. Outram, Mark Robinson, Patrick Roberts, Francisco J. Aceituno, Gaspar Morcote-Ríos and T. Michael Keesey

Jorge Peña and Fernando Urbina of the National University of Colombia believe that the paintings may be much more recent than the last ice age. In their 2016 publication “War dogs, horses, cattle and other themes in the rock art of the Serranía de la Lindosa (Guayabero River, Guaviare, Colombia): A conversation” they argue that many of the paintings in La Lindosa might be much newer, even post-European-contact. If the paintings are only a few hundred years old, it would explain their exceptional state of preservation, but would certainly rule out interpretations of pre-historic humans hunting ice-age megafauna.

Urbina says: “(The paint) shows a quadruped with an offspring, caught in a trap. Its size, in relation to the human figures facing it, could suggest that it is extinct megafauna. However, the exaggeration in size may depend on various symbolic reasons. Also, it could happen that the human figures correspond to children or dwarfs, or dwarf children. Federmann in his chronicle speaks of the encounter with members of an ethnic group of very short stature. Finally, it could be perspective management”

Until we have better estimates on the age of the paintings (which could happen as soon as late 2022), the question of the species remains unanswered. Do these mysterious cliffside drawings capture the brief moment of overlap between the last of the giant ground sloths and the first humans of South America? What did the drawings mean to the artists that created them? What animals did they see, what stories went along with the pictures, and what would they have to say to us about the splendor of the world as it was?

-Cecilia Pamich & Ames Reeder

The Origin of the National Symbol

The Origin of the National Symbol

Team Sloth contacted Jorge Carballo, the man responsible for the idea to declare sloths the national symbol for Costa Rica. Jorge grew surrounded by lush tropical forests and is passionate about nature.

Costa Rica is a paradise in so many respects. The fact that you can find wildlife in your backyard– toucans, monkeys, or sloths feeding or passing through—makes this country a special place. This is exactly how Jorge’s childhood was: a constant contact with nature and animals.

This love for nature eventually grew into the initiative that made sloths the latest national symbol of Costa Rica.

The following transcript has been lightly edited for clarity.


cart costa rica

Jorge, tell us about yourself:

I was born in Limón, but I lived in Guápiles until I was 19 years old. Then I went to study Communication in Buenos Aires, Argentina in 2010. I returned to Costa Rica about 3 – 4 months ago, and now I work for a tech company as a UX Researcher.

Where does your love for nature and sloths come from?

I think it is a product of the environment in which I grew up. From the proximity to the forests that I had for all of my childhood, the contents of my school, and the idiosyncrasy of a country that is entirely loaded with environmentalism. Coexistence with nature is part of the imagination of the Costa Rican. Perhaps this seed does not grow with the same strength in everyone, but the seed is there.

With sloths, this bond is sustained by their characteristics: they are non-aggressive, they are very pretty, they seem to be smiling, and they spend many hours sleeping. They are very noble animals. And their slowness makes them very funny. It is very difficult not to have sympathy for them. Sloths were always there “in the mountains”, and since I was in contact with those spaces, it was not uncommon for me to see them.


national symbol costa rica
Jorge and his brother Christian exploring the Caribbean forest


How did the idea of the sloth as a national symbol come about?

The idea was born from a tweet I read. This person said that the sloth had to be a national symbol, like a joke. Then I shared the tweet with a couple of people. That sparked a conversation, questions, and some research. Little by little the idea became more and more concrete, more solid.

I mentioned this idea to Congresswoman Yorleny León, whom I have known for more than 10 years, and she told me that I could count on her to support it. After a lot of work, the project finally became serious and it ended up national law. It’s amazing, I still can not believe it.

I was surrounded by people who worked with me, who added their effort and desire to make this happen. I definitely wouldn’t have done it alone.

How was the process to write the project?

It was definitely a challenge, but a very cute one. While I had some research and writing experience from my work, I had never done anything legal – legislative. Luckily I was surrounded by people who were able to go where my knowledge could not, and they offered me their full collaboration as if this project were also theirs; as if it belonged to everyone.

It was a project that involved a lot of learning and surprises about the animal. It was also really good learning how much sloths are loved in the world. It is not every day that we have the opportunity to work with something so beautiful and interesting. Maybe that is what made it easier to sit down on the weekends to work on the project: look up information, write, structure, revise, rewrite, look for more information, revise, and so on several times.

I also had Yorleny’s team and that gave me some peace of mind. I was not alone, I did not work alone. I had many advantages, many factors that worked in my favor, but I think what really made the difference was the seriousness with which the project was ultimately taken. That was the key. Going from a wish to a specific job that is now a national law. And that is truly a luxury. I am very happy to have participated in this.


Congresswoman Yorleny León Marchena national symbol
Congresswoman Yorleny León Marchena promoting the project

Why is it important to declare the sloth a national symbol?

Beyond the fact that it is a very beautiful animal, the decision was more strategic than whimsical. The context in which the project was presented was very favorable for its success. Today the sloth enjoys a level of acceptance and good publicity that no other animal in the country has.

That happens both inside and outside the country. The animal is associated with Costa Rica in the imagination of the people, although it also exists in other countries. The memes, the movies, the merchandise, the t-shirts that tourists wear, the comic strips in the newspapers, in short, sloths are everywhere.

So we had to do something. Costa Rica had to take advantage of this opportunity. That’s how this idea began to be conceived: the project had to bring together a number of positive factors to happen simultaneously, to achieve very good things. Good things not only for sloths but also for other animals and the space they inhabit, such as national tourism and environmental education of children in schools, scientists, and the world.

Because we are not only protecting the sloth, we are also creating a precedent to be replicated in other places. This is an experience open to be improved, a seed that can continue to grow.



How do you imagine that this declaration will benefit the conservation of sloths (and wildlife in general)?

I envision two large groups of benefits. The first, more abstract, would be the privileged place that sloths reaffirm in the imagination of the people. Now children are going to learn more about them in schools, older people will see them with more respect. They will never go unnoticed again. I do not remember that any other animal has received so much positive press in the country.

There are still people who do not know sloths exist. There are people who do not know that they exist in Costa Rica. There are people who do not know that what they thought was a leaf or a nest in the tree behind their house is a sloth, but now sloths are being recognized. Today with their faces they tell us “here we are” and now everyone knows it. And that’s good.

The second group would be the most concrete benefits. I am referring to those involving state institutions such as the Ministry of Environment (MINAE), MOPT, ICE and their specific actions such as protecting or expanding habitat areas, placing safe passages for wildlife on highways, and improving public electrical wiring to avoid electrocutions, just to mention a few. In summary, I hope for better living conditions for the sloth and consequently for many other animals.

What is your favorite species of sloth?

That is a difficult question. I have my favorites. Nationally, the three-fingered sloth (Bradypus variegatus) is my favorite. I really like their faces, the shape of their noses, and the black lines in their eyes. Also, I like the hair. Internationally, I love the pygmy sloth (Bradypus pygmaeus) in Panama. They are like a three-fingered mini version. They are endemic to an island and they are small, almost like a character from a legend. Unfortunately, they are endangered. Maybe the next project could be about the pygmy sloth.


What is your favorite fact about sloths?

I am struck by how modest they are when it comes to defecating. I say modest but there may be a more primary reason, more biological and less “cultural” or social, but it is very funny that they take the trouble to go down, make their hole, and after doing their thing, cover it. It is a risky activity because they can die from being exposed to predators that can reach them.

It is almost nonsense. But I think that regardless of how funny this data may be, I also like it because there is still no solid idea why they do it. That mystery seems powerful to me because it reminds us that despite all the advances we have made and all the research there are still things to discover, things to do.



Tales from the Jungle: July 2021

Tales from the Jungle: July 2021

July is always an eventful month for Team Sloth, but we weren’t prepared for what was lurking around the corner this year!

Things got off to a good start as we celebrated an important symbolic achievement and a huge milestone for one of our projects.

Unfortunately, we also experienced the wrath of Mother Nature in all her glory – with earthquakes, tropical storms, and severe flooding leaving our team stranded!

A new national symbol!

July got off to a great start with Costa Rica declaring the sloth as their new official national symbol! This means increased protection, awareness, and more funding for conservation and research (hooray)! We are proud to have been involved in this project as consultants for the Legislative Assembly. You can read more about our contributions and suggestions here.


national symbol costa rica

100 Sloth Crossings!

This month we also installed our 100th Sloth Crossing – that is 100 new places where sloths can now move safely from tree to tree! We couldn’t have done this without our incredible Sloth Crossing donors and sponsors – thank you! By joining our Sloth Crossing community you can receive exclusive updates, photos, and videos from our network of wildlife bridges (find out more using the links below):


sloth crossings

More Castration Clinics!

Our ‘Oh My Dog’ team continued to make waves this month by hosting their 4th major dog castration clinic in the last 12 weeks. 42 vulnerable dogs were spayed and neutered in one day at an indigenous community center in the South Caribbean! This project helps to reduce the stray dog population in the region which is a major threat to all types of wildlife – including sloths!





Teaching old dogs new tricks!

Our dedicated dog team also ran our second “Oh My Dog Academy” training course this month which kept everybody on their toes – including the dogs! We provide these specialized training courses for free to local communities and aim to prevent problematic dogs from attacking wildlife. Through these courses, we have already trained over 60 dogs in the South Caribbean!





The meaning of volunteering

“After we get around the sewage pipe, make a jump for the mud bank. You have boots, right? I think it’s only about ankle-deep,” Sarah tells me as she maneuvers around the chest-height pipe. “But watch out for the live electrical wire. And the bees.”

SloCo volunteer Ames has written another entertaining blog entry about life on our sloth tracking team!


binoculars tracking




What Went Wrong…

Apparently, it isn’t always sunshine and sloths in the Caribbean! Here we reflect back on some of the things that didn’t quite go to plan this month…


When it rains… it pours! 

Last week the South Caribbean was battered by multiple tropical storms which brought record-breaking rainfall to the region. The floods were catastrophic and thousands of people were seeking refuge in emergency shelters. Thankfully Team Sloth are all safe and well – albeit a little bedraggled.


Albergues suman casi 100 personas atendidas por graves inundaciones en Limón |

Cut off from the world!

During the storms, the only bridge that connects the South Caribbean to the rest of the country collapsed leaving the entire region isolated and underwater. Unfortunately, this means that half of Team Sloth have been unable to return home, and we are still waiting for the authorities to reconnect the road! EDIT: The bridge is now fixed!


Puente que colapsó por lluvias fue declarado en condición “alarmante” desde 2018

An unexpected rescue

During our castration clinic, a man arrived with two dogs in terrible condition (one was found inside a tied bag). Upon seeing this suffering, Team Sloth persuaded the man to surrender his dogs so that we could find them loving homes. Sadly one of them didn’t survive the ordeal, but we were able to rescue the other one and she has now been adopted by a wonderful family!


The jungle Vs electronics.

The battle between the jungle and modern technology continues…! The warm, humid conditions destroy electronic equipment at an alarming rate, and the latest victim was our tracking receiver! This is a vital piece of very expensive equipment that we were horrified to find malfunctioning! Thankfully we have an old spare to use while our main unit is repaired.


tracking receiver


Shaking things up!

Just days before the tropical storms hit, the South Caribbean was also rattled by a magnitude 7 earthquake which gave everyone a good fright! Thankfully there was no major damage or injuries, but it was a good wake-up call to remind us of the strength of Mother Nature!


Almacén Super Negro, Home Creek - YouTube

An Extreme month

July was a month marked by extreme weather events in a region which usually enjoys a relatively calm tropical climate. Species like sloths which have evolved to live in these warm and stable conditions often struggle when faced with big changes in the environment.

It seems like every day we hear new reports of extreme weather and natural disasters shaking the world. Every now and then these incidents touch us closely, and unfortunately, the frequency and intensity of these extreme events are increasing.

Anthropogenic global warming is a threat we have to take seriously, as is the loss of biodiversity. Thankfully we are a resilient species, and we know that we can achieve incredible things when we choose to work together.

We don’t yet fully understand the impact that the storms have had on sloth populations in the South Caribbean, but we will continue to do everything that we can to help.

We are looking forward to enjoying a drier and hopefully less dramatic August – I look forward to sharing our progress with you!


All the best from the jungles of Costa Rica,

Rebecca Cliffe

Founder and Executive Director

The Sloth: A New National Symbol for Costa Rica

The Sloth: A New National Symbol for Costa Rica

National symbols are culturally created images to represent the country and preserve collective memories about these icons. Usually, these symbols include national anthems, flags, shields, animals, flowers, trees, national dishes, and languages.

Some of the most important national symbols of Costa Rica are the flag, the national shield, the flower ‘Guaria Morada, the Guanacaste tree, the white-tailed deer, the clay-colored thrush (Yigüirro), a percussion instrument called ‘Marimba’, coffee, and Manatees.

And now, thanks to the initiative of legislator Yorleny León Marchena, the sloth has recently become a new icon for the ‘Pura Vida’ country.


national symbol
Photo: Suzi Eszterhas

Already an icon

The sloth became an unofficial symbol many years ago. In a way, it does represent the spirit of the Costa Ricans, as expressed in the official document written by legislator Yorleny León Marchena. Just like sloths, Ticos (the local term for Costa Ricans) are known for their peaceful attitude, slow-paced life, and little stress. Costa Rica is considered one of the happiest countries in the world, and the happiest in Latin America.

Sloths have long been used as the main ambassadors to promote tourism in Costa Rica, as you can see in this great promotion video featuring a three-fingered sloth as the main character:



The project of turning sloths into national symbols was the perfect opportunity to develop specific actions from the government and individuals to improve the lives of sloths in Costa Rica. So of course, we were ready to jump in and help.


Reasons to make the Sloth a National Symbol of Costa Rica

  • It creates awareness among Costa Ricans as well as foreign visitors to become aware of the importance of protecting our forests and their vulnerable inhabitants.
  • It would promote the creation of new wooded areas and the protection of existing ones, for the safe conservation of sloths and other wildlife.
  • It would help generate more tourism with an environmental emphasis.
  • Different reforestation and conservation strategies could be developed with state entities and/or private entities, from a new more targeted perspective.
  • It would encourage the planting of sloth-friendly tress such as the guarumo (Cecropia peltata), by individuals, in agricultural and semi-urban zones, thus restoring vital biological corridors.
  • It would promote scientific and medical research related not only to the sloth but to all living beings that inhabit the forested areas of the country. The ecosystems with the greatest amounts of trees are also some of the most poorly understood ecosystems in the world.


costa rica National Symbol
Copyright: Suzi Eszterhas

The Draft

When the idea of this project was revealed by the national media, we immediately contacted the legislator in charge to offer our insights and experience on sloths. Gladly, just a few days later, we were contacted by the Legislative Assembly.

The project encouraged the Ministry of Environment to watch for the populations of sloths, protect the areas where they live, and identify key areas for conservation. It required the Ministry of Public Infrastructure to help regulate speed limits in key areas.  The draft also included a special educational program to be implemented by the Ministry of Education.

Although the project proposal was already quite good, it lacked some concrete actions that we considered vital to protect sloths in the wild: it didn’t mention the main conservation problems for sloths in Costa Rica: lack of scientific research, electrocutions, and dog attacks.


camera trap crossing

Institutions involved

The following is a list of the institutions that were involved and provided suggestions to the legislators.

  • Cámara Nacional de Turismo (CANATUR) National Chamber of Tourism
  • Instituto Costarricense de Electricidad (ICE) Costarrican Electricity Institute
  • Instituto Costarricense de Turismo (ICT) COstarrican Institute of Tourism
  • Ministerio de Ambiente y Energía (MINAE) Ministry of Energy and Environment
  • Ministerio de Educación Pública (MEP) Ministry of Education
  • Ministerio de Obras Públicas y Transportes (MOPT) Ministry of Transport and Public Infrastructure
  • Sistema Nacional de Áreas de Conservación (SINAC) National System of Protected areas
  • The Sloth Conservation Foundation (SloCo)


Our Suggestions

We wrote a list of suggestions based on our research and experience working in the field. Although we knew some of these suggestions would be complicated for a country like Costa Rica to enact, we had to give it a shot.

1) Supporting sloth science:

Because information on the ecology of sloths is scarce and in some cases, even basic data on natural history and ecological requirements are lacking, research and scientific knowledge are necessary for the creation and development of the best conservation strategies. Currently,  there are no accurate population counts of sloths in Costa Rica, making it difficult to determine the conservation status of both species in the country.

It is necessary to know the population trends through censuses, as well as to support studies on the genetics of the populations within the country. Therefore we suggested providing incentives of any kind for scientific studies, both from public and private institutions, such as universities, local governments, and/or non-governmental foundations.


costa rica national symbol
Photo: Suzi Eszterhas

2) Insulating power lines:

Electrocution of wildlife is a big problem that particularly affects sloths: at least half of the animals electrocuted in the South Caribbean are sloths. The death rate after electrocution is very high. For this reason, we recommend prioritizing the isolation of existing single-phase, three-phase, and transformer lines by the company corresponding to each jurisdiction in areas where there is a high population density of sloths and considerable reports of electrocuted fauna.


power line electrocutions


3) Releasing rescued sloths:

Our latest research on sloth genetics reveals that there are differentiated populations, and some have been affected by translocations carried out by both MINAE and rescue centers. Sloths are estimated to account for nearly half of the mammals admitted to sanctuaries and rescue centers. For this reason, we consider it of utmost importance that the competent authorities, advised by experts on the subject, develop a coordinated, nationwide protocol for the rehabilitation and release of sloths.


Costa Rica national symbol
Photo: Suzi Eszterhas

4) Creating a national database:

With regard to wildlife centers that admit injured and rescued animals, we proposed the creation of a national database where the statistics of these institutions would be made public. In this way, accurate information will be available on the number of sloths that enter these centers, and the reasons for their admissions. These comprehensive reports would create a more accurate picture of the issues that sloths face in particular areas in order to create consistent solutions.


costa rica national symbol
Photo: Suzi Eszterhas

5) Addressing the issue of free-roaming dogs:

According to public statistics from some rescue centers, dog attacks on sloths are becoming a recurring cause of admission. This is why we suggested reinforcing compliance with current laws on pet ownership from the corresponding agencies. The uncontrolled free-roaming and stray dog ​​population are not only a public health problem in general but also directly affects sloths and wildlife. We suggested more education campaigns on responsible dog ownership, and more frequent large-scale spay and neuter campaigns, especially in the regions where this problem is more prevalent.


dog castration


The final project


ARTICLE 1- Declaration

The two-fingered sloths (Choloepus hoffmanni) and three-fingered sloths (Bradypus variegatus) are declared national symbols of Costa Rica’s fauna and of the country’s commitment to protecting forests.

ARTICLE 2- Institutional competence

It corresponds to the Ministry of Environment and Energy (MINAE):

a) To ensure the adequate conservation of the sloth populations existing in the Costa Rican territory and to ensure the proper protection of the natural habitat of this species, especially the restoration of river protection areas.

b) Define, through technical studies, the list of priority places and critical habitat for sloth connectivity, as well as their threats and the genetic status of the populations.

c) Enforce all laws and international conventions that are related to the conservation and protection of the sloth and its habitat.





It corresponds to the Ministry of Public Works and Transport (MOPT):

d) Promote the regulation of speed limits, of the different means of transport, in the vicinity of sites duly identified as sensitive for the free movement of sloths; both around protected areas and outside of them.

e) Implement aerial wildlife crossings on national routes based on the implementation of the Environmental Guide: Wildlife-Friendly Pathways.

f) Define, through technical studies, the list of priority places with the greatest amount of wildlife-vehicle collisions of sloths and other wildlife species.

g) Coordinate with the Municipalities the implementation of aerial wildlife crossings on cantonal roads and ensure that roads located in natural resource protection areas or that intersect wildlife passage routes must have adequate structures that facilitate freedom of movement.  Passing from one side of the road to the other, in the places where the studies so determine.


costa rica national symbol
Photo: Suzi Eszterhas


It corresponds to the Costa Rican Electricity Institute (ICE) and private electricity companies:

h) Implement measures to reduce electrocutions with power lines, applying the Guide for the Prevention and Mitigation of Electrocutions of Wildlife by Power Lines in Costa Rica.


sloth on power line

ARTICLE 3- Education and awareness programs

The Higher Education Council, in coordination with the Ministry of Public Education, may include the protection of the sloth and its natural habitat in its educational and awareness programs. For this purpose, the Ministry of Environment and Energy and its decentralized bodies and its institutional departments may advise.
Other government institutions, non-governmental organizations, public and private companies may also develop initiatives that promote the conservation of sloths and their habitat, in accordance with the provisions of the current legal system, particularly Law No. 7554, Organic Law of the Environment, of October 4, 1995, Law No. 7317, Wildlife Conservation Law, of October 30, 1992 and their respective regulations.


teacher sloth booklet

ARTICLE 4- Responsible tourism

The Costa Rican Tourism Institute (ICT) may use the image of the sloth for its advertising campaigns, locally and internationally, in accordance with the provisions of the current legal system, particularly Law No. 7554, Organic Law of the Environment, of October 4, 1995, Law No. 7317, Wildlife Conservation Law, of October 30, 1992 and its respective regulations.
In addition, it may develop, in coordination with SINAC, actions, and protocols that promote good tourism practices that allow the protection and sustainable tourism with regard to sloth species.


sloth selfie


Most of our suggestions were considered: support for the scientific research support (Article 2, section b) and the prevention of electrocutions (Article 2, section h). It’s also thrilling to see the promotion of Sloth Crossings all over the country as well! (Article 2, section g).

According to the official document “the suggestions to include a sloth release protocol, the generation of databases, and the issue of pet management, specifically stray dogs,  was beyond the scope of the proposing legislator. However, those of us who signed this opinion consider that the general framework of the law does allows competent institutions to address these issues moving forward.”


beach almond national symbol costa rica
Photo: Suzi Eszterhas


So even if these points were not specifically included in articles and sections, this is still some uplifting news!

An interesting point made by MINAE and SINAC is that although both species of sloths are listed by CITES as ‘Least Concern, both institutions consider sloths to be endangered in Costa Rica.

We consider this is a huge step in formally recognizing and promoting all the conservation efforts we were carrying for the past few years. We feel a new future is on the horizon for sloths in Costa Rica, and we’re extremely happy to be part of it.


-Cecilia Pamich

Chief Operations Officer

Tales from the Jungle: June 2021

Tales From the Jungle: June 2021

A month to remember…

June has been an emotional rollercoaster for Team Sloth. We sadly witnessed some of the most cruel, greedy, and reckless sides of humanity, but we also managed to achieve some fantastic breakthroughs for sloth conservation.

The month started with us discovering that one of our sloth study sites had been completely (and illegally) deforested. One of the few remaining green areas in the South Caribbean cleared for development and profit – leaving countless sloths homeless and stranded.




One sloth was trapped on power lines, while 4 others were found sitting on the ground in isolated bushes surrounded by dogs (including a mom with a small baby). All of them had to be relocated to a nearby patch of forest.




We saw other sloths pushed into tiny remaining forest fragments surrounded by roads and concrete. 5, 6 sometimes 7 sloths all trying to share one tree and fighting over space.


sloth in fence deforestation


And to top it all off, we then found two violent and drunk men attacking a female sloth with her newborn baby – and when we tried to intervene, they got aggressive with us. There was nothing we could do except alert the relevant authorities and hope they eventually stopped.




Thankfully, after what felt like an eternity, the men left her alone and she was able to climb safely back up the tree. Although she was clearly very frightened and stressed out, she didn’t appear to have any physical injuries.




While situations like these often leave us feeling utterly hopeless and deflated, we will not give up. We must remember that meaningful and permanent change takes time, and saving sloths isn’t just about working with the sloths themselves. We have to consider the ecosystem as a whole – and that includes humans.

It is after witnessing heartbreaking moments like this that we feel more determined than ever to push forwards with our projects and fight for a brighter future. Thankfully, the rest of June was much less gloomy (but equally as chaotic – as usual)!


mom baby
When you hit rock bottom, the only way to go is up! This mom and baby two-fingered sloth were rescued from a bush surrounded by dogs after their home was cut down. They were released into a safe forested area.


June Highlights

tortugueroExpanding into Tortuguero

Last month we expanded our sloth conservation efforts to include Tortuguero (where there is no road access, and 3000 dogs live alongside just 1600 people). We ran a major dog castration and vaccination clinic, built some Sloth Crossing bridges, gave education materials to the local children, and also hosted a beach clean-up event! In case you missed our previous newsletter, you can read about it here.




Loving All Sloths!

June is Pride Month, and here at SloCo we celebrate and love diversity! We are a diverse team with people from different identities, backgrounds, ethnicities, and nationalities. Ames is one of our volunteers for the Urban Sloth Project and he has written this short (and very entertaining) blog describing a day in the life of a volunteer at SloCo!





castrationMore Castration Clinics!

As we continue with our mission to reduce the number of dog attacks on wild sloths, we held two more major castration clinics this month to spay and neuter dogs in the Caribbean. Over the course of one day, Team Sloth castrated over 70 dogs from rural indigenous territories – which brings our grand total to almost 200 dogs spayed and neutered in the last 2 months!





Where the Jungle meets the Sea

This month we embarked on a major reforestation effort along the beaches of the South Caribbean in collaboration with local non-profit Coral Conservation. With the help of 40 volunteers from the local community, we planted over 200 sloth-friendly trees along the beach to mitigate the impacts of ocean erosion and global warming on coastal sloth habitats!





Beach Bridges

This month we received official permission from the Costa Rican government to install 20 new wildlife bridges in public areas along the beach in the South Caribbean. This important strip of the forest is protected by law and is home to a large sloth population but has recently become fragmented due to coastal erosion and illegal developments!





babyMore Urban Sloths!

This month we expanded our Urban Sloth Project by adding FOUR new feisty sloths to the mix! We will introduce each sloth’s story in a separate newsletter next week, but the four newbies include Arthur, Mango, Nacho, and Baguette (there is apparently a food theme emerging with our sloth names)! They all live in different levels of “urban” habitats and will be teaching us a lot over the next 2 years!





What Went Wrong

As always, it was not all sunshine and sloths this month! Here are our favorite fails of June…. because we believe that success stories are not the only kind that needs to be shared!


Are you afraid of spider… monkeys?

While dangling over 30 meters in the air installing a Sloth Crossing, Team Sloth’s Tamara had a very close encounter with a troop of angry spider monkeys. Thankfully she managed to make a quick descent from the canopy using the safety ropes  – you can never say it’s boring working for Team Sloth! You can read the full story here.




Slingshot fail

This massive slingshot is crucial for installing wildlife bridges as it helps us to launch the ropes high in the trees. For Team Sloth’s trip to Tortuguero this month it was the most important item on the packing list… but of course it was the only item we forgot! Thankfully, our creative team managed to build those bridges anyway!





Stuck in the mud

Working in the jungle is never easy, which is why we need to use all-terrain vehicles. Unfortunately, the slippery jungle mud and heavy rain proved too much for the SloCo 4×4 this month and we spent a lot of time stuck in the mud (of course this happened at the most inconvenient time possible while all the sloth action was unfolding)!





A tetanus shot needed!

Tracking Urban Sloths might sound easy, but we quickly discovered that is not the case. One of our new sloths has made the questionable decision to live in trees surrounded by a stinking swamp and a rusty barbed wire fence. While trying to reach her, I got myself tangled in the fence and needed to get an emergency tetanus shot!





I hope you enjoyed reading about our highs (and lows) this month. While June undoubtedly started off on a bad note, we certainly ended on a positive and we are determined to continue moving forwards and doing everything in our power to make a difference.

We couldn’t do it without you – so thank you for your ongoing support. We will be back with more updates soon, but for now, I hope you have a wonderful weekend!


All the best from the jungles of Costa Rica,


Dr. Rebecca Cliffe

Tortuguero: Wildlife bridges, castration clinics, and more!

Tortuguero: Wildlife bridges, castration clinics, and more!

Last year Team Sloth were thrilled to receive an invite to visit the Tortuguero National Park on the Caribbean Coast of Costa Rica.  Tortuguero is renowned as one of the most important turtle nesting sites in the whole world, and in particular, its white sand beaches are a haven for endangered green sea turtles. 

We were excited to be connecting and forming new collaborations with a range of different local conservation organizations in the area, and this trip was an opportunity to learn more about the problems in the region and to come up with mutually beneficial solutions to help both the people and the wildlife. 




Sadly, it quickly became apparent that the global pandemic had hit the village of Tortuguero hard. Historically, the residents of Tortuguero used to sustain themselves by harvesting the turtles for food, trading the turtle eggs, and creating items to sell from the shells.

Thankfully in recent years, the economic benefit of the turtles has slowly shifted away from exploitation and towards ecotourism, but this industry took a hard hit in 2020 and many local families found themselves in difficult positions. 



A unique town

These issues are exacerbated by the fact that Tortuguero is a small, isolated town with no road access and absolutely no veterinary resources. The nearest vet clinic or wildlife rescue facility is over 2 hours away and can only be reached by a combination of boat and bus!

The dog population of the town now outweighs the human population 2:1, with 3000 dogs living alongside 1600 humans, and a lack of castration opportunities means that this problem is getting rapidly worse.

The large dog population is troublesome for a variety of reasons. A large outbreak of canine distemper this year threatened not only people’s pets but also raccoons, foxes, and even jaguars – a rare species that is already extremely vulnerable.

Unfortunately, dogs are now contributing to the rapid extinction of over 180 different wildlife species. In Tortuguero, they are attacking sloths as they move on the ground between trees, and they are also killing the sea turtles as they emerge onto the beach to lay their eggs. As an endangered species that is so closely intertwined with the livelihoods of the local community, Team Sloth felt impassioned to help restore the balance. 


Organizing castration campaigns and beach clean-ups

After returning from our initial visit to Tortuguero last year, we began to hatch a plan that would benefit the community, the wildlife, and the dogs. 

Working alongside Asociación Voluntarios de Costa Rica (ASVO), Sistema Nacional de Áreas de Conservación (SINAC), Ministerio de Ambiente (MINAE), the Sea Turtle Conservancy, and Comité Ambiental Tortuguero, we organized and funded a major castration and health clinic for the dogs of Tortuguero.


dog clinic tortuguero


But why stop there? Because we often like to bite off more than we can chew, we also decided to build some Sloth Crossing canopy bridges, do some education outreach with the local children and also host a beach clean-up event at the same time! 


beach clean up tortuguero

Saving turtles and sloths by helping dogs

After a 4 hour, beautiful boat ride down the canals from Moin to Tortuguero, Team Sloth arrived late at night ready to begin the castration clinic the following morning. We brought a team of fantastic volunteers along, and together with veterinarian Maricela, Mina Escot, and the ASVO volunteers, we were able to castrate 42 dogs in one day!




Some people had even traveled to the clinic by boat and we had to carry their (still slightly sleepy) dogs back to their boat to head home! In the meantime, the rest of Team Sloth had ventured out into the local area with ASVO to start installing Sloth Crossing wildlife bridges!


Bridging more gaps

Over the course of the next few days, the bridge-building team had quite an adventure! They were able to install 6 new Sloth Crossing bridges, used over 200 meters of rope in trees that were over 40 meters high, and managed to reconnect some important areas of the national park that had become isolated due to fallen trees. However, in true SloCo style, they also managed to encounter quite a few disasters along the way! 




There were ant nests in people’s shoes, broken slingshots, missing equipment, torrential rain, and some accidental injuries, but perhaps the most precarious moment happened while finishing off the very last bridge of the trip. 

Tamara is a fully trained climber and is Team Sloth’s chief bridge builder. She was dangling at the top of a 30-meter tall tree trying to secure the rope to a branch when she noticed a troop of wild spider monkeys bounding through the canopy towards her. These magnificent and rare primates are spectacular to watch in the wild, and at first, she was excited to be having such a close encounter with them.


spider monkey tortuguero


Unfortunately, she quickly realized that they weren’t quite as happy to see her as they started to get a bit too close for comfort. They were no doubt confused by the strange human dangling in one of their favorite trees, and they weren’t afraid to let her know about it. They surrounded her in the tree and began to scream at her while showing their teeth.

Her instinctive response was to scream right back at them to show that she wasn’t afraid, and so for an uncomfortable amount of time, Tamara and the monkeys were yelling at each other and having a stand-off in the tree.

At the same time, she somehow managed to finish securing the rope and got her equipment ready to make a quick descent from the canopy using the safety ropes. Once her feet were back on solid ground she breathed a big sigh of relief – you can never say it’s boring working for Team Sloth!


tortuguero bridge


Due to the ongoing impacts of the COVID-19 pandemic, we, unfortunately, weren’t able to host our usual Sloth School events in the local schools. Our education team didn’t give up, however, and they decided to go door to door instead! They delivered education packs to over 50 families in Tortuguero and are busy making plans to host a major outreach event as soon as the government declares it safe to do so. 


Together we go further

Lastly, we want to thank YOU for everything that you have done to support our work to protect sloths. We would not be able to run projects like this without you! 

Thank you also to SINAC/MINAE at Tortuguero National Park, Mina, James and the ASVO volunteers, our vet Maricela and her team, CAT and STC at Tortuguero – none of this could have been done without you!

We are now aiming to return to Tortuguero in September when we hope to build more wildlife bridges, castrate more dogs, and further help the community of Tortuguero!


sloco team


-Sarah Kennedy

Director of Education & Outreach

Oh My Dog Project Manager


Tales from the Jungle: May Update!

Dogs, Goats, and Missing Sloths

Team Sloth have been the opposite of slothful this month – we have been chasing invisible sloths through the jungle, carrying out emergency surgeries, castrating dogs and we were shamefully outsmarted by a herd of hungry goats. Read on below to learn about our biggest successes and failures this month!

Sloth Crossing in Action!




We use remote camera trap technology to monitor our Sloth Crossing wildlife bridges, and this month we were delighted to discover that one of our bridges has turned into a major highway for lots of different species – including both species of sloth, monkeys, and even kinkajous! Click here to view the images!


Our First Castration Clinic!


dog castration


After months of preparation, we were finally able to host our first castration clinic this month in collaboration with veterinarian Ileana Núñez Ulate.  We were able to castrate dogs for 21 local indigenous families in the South Caribbean which will help to reduce the number of dog attacks on sloths in the future!


Tarzan’s Return to the Jungle!


surgery sloth

Tarzan is a three-fingered sloth that arrived to a local rescue center with a badly broken arm. He needed specialized surgery to repair the bones, but the rescue center did not have the funds available due to the ongoing pandemic. We were delighted to step in and fund Tarzan’s surgery, and he is now recovering and preparing for release back into the wild!


Chasing Sloths with Suzi


suzi eszterhas sloth

This month we are also delighted to host world-renowned wildlife photographer Suzi Eszterhas who is here in the South Caribbean photographing sloths and the conservation problems that they face. We will be able to share her images with you soon, so stay tuned! You can also check out her work to support young girls in wildlife photography: ‘Girls Who Click’!


Back to School!


school south caribbean


We were relieved this month to be able to resume our in-person sloth lessons in local schools in Costa Rica! We are also happy to have welcomed Kassandra into Team Sloth as our new Education Officer in the South Caribbean! Don’t forget – if you are a teacher you can still contact us to organize a free virtual lesson (in English or Spanish) wherever in the world you are!


Reforestation Records!



This month we planted our 700th tree since the beginning of 2021 and connected 28 new properties as wildlife corridors in the South Caribbean! We have also formed new partnerships with other local organizations with the joint aim to reforest coastal areas. This will help not only sloths but also many other species – including endangered sea turtles!

Check out this map to see our tree plantations and wildlife bridges!

New Sloth Backpack!




Earlier this week we were fortunate enough to find Alan – one of our Urban Sloths – sleeping very low down near the ground! This was the perfect opportunity for us to give him a full health check and also fit him with a brand new Sloth Backpack! He will wear this backpack for the next 3 weeks and he will hopefully teach us a lot about urban sloth ecology!


What Went Wrong

It isn’t always sunshine and sloths! Here are our ultimate fails this month…. because we believe that success stories are not the only kind that needs to be shared!


You’ve Goat to be kidding me


Whenever we plant trees, we always monitor the health of the saplings for the first few years to ensure survival. Unfortunately, we didn’t anticipate a goat invasion. One concerned property owner called us this month because some goats had broken onto his land and eaten all the trees we planted…!


Sloth School shut down


school education

Just 3 days after we finally resumed our in-person sloth school education program, the authorities of Costa Rica announced that schools would be immediately suspended again due to an increase in COVID-19 cases. Sometimes we just have to channel our inner sloth and be patient…


A Surprise Setback


dog castration

Our first castration clinic turned into a marathon 12-hour day when our vet discovered a severe uterus infection in the very first dog! We had to complete an emergency surgery to save the dog’s life, but thankfully everything went well (and we had plenty of coffee on hand to keep the team going)!


Missing In Action



We know that sloths are good at hiding, but we are usually able to find them if we look long and hard enough! Unfortunately, Arthur (the latest addition to our Urban Sloth Project) decided to challenge us on that fact. After we released him, he managed to avoid detection for 4 full weeks!


Taxidermy Fail


harpy eagle museum taxidermy

While this is not technically a failure on our part, we thought it deserved a place on this list! On a recent visit to the Costa Rican Natural History Museum, Team Sloth discovered some quite spectacular sloth taxidermy on display. Words can’t really do this justice – see them for yourself in our blog post!


I hope that you have enjoyed our updates this month – what a busy month it has been! We already have a lot of exciting events lined up for June, including expanding our sloth conservation efforts to include a whole new region of Costa Rica! I look forward to sharing more updates with you soon and thank you as always for continuing to support our work. We couldn’t do any of this without you!

All the best from the jungles of Costa Rica,
Dr. Rebecca Cliffe
Founder and Executive Director

Did humans cause the extinction of the giant ground sloths?

Did humans cause the extinction of the giant ground sloths?

“We believe that human beings are mainly responsible for the extinction of megafauna in South America,” said Luciano Prates and Ivan Perez, CONICET researchers at the Faculty of Natural Sciences and Museum of the National University of La Plata, Argentina, and authors of a scientific study on the matter, which is published in the journal Nature communications.

Based on a vast amount of data collected via fossil and archaeological records ranging across the entire subcontinent, their work associates the hunting activity of the first groups of people with the demographic decline, and subsequent disappearance, of all large mammal species, occurring at the end of the Pleistocene Epoch (also known as the Ice Age), between 13 and 11 thousand years ago.


Recreación de cómo era la cacería del perezoso gigante
A recreation of humans hunting giant sloths / Illustration: Alex Macclelland, Bournemouth University

The fish tails

This study contradicts the widely accepted hypothesis in South American archeology: that large animals disappeared as a result of environmental changes. It was thought that the increasing temperatures and changes to vegetation resulting from the previous ice age (about 18 thousand years ago) was the catalyst which led to a mass extinction.

Instead, the new research focuses on where temporal and geographical evidence coincides, specifically where megafauna and ‘fish tail’ spearheads overlap. This very specific type of spearhead is similar to the ‘Clovis’ spearhead, which existed only in North America and is closely associated with hunting mammoths.


The “Fishtail” spearheads defining feature is that they are “bifacial” (having two faces). They tended to be symmetrical and made of many different types of stone such as chalcedony, opal, or jasper, which are ideal for carving due to their high silica content./ Photo: Museo Colonia


Clovis point | pleistoscenery
Preserved ‘Clovis’ points, like this one, were the first clear evidence of human activity in North America. These spearheads were used by the Clovis people to hunt large animals, and it’s existence coincides with the extinction of mammoths, giant sloths, and giant bison in North America./ Photo: pleistoscenery


“In both cases, they are large, broad tools with a very sophisticated technology,” Prates describes,  “Their existence is very short-lived: they only appear between 13 and 11 thousand years ago and they are not found any earlier on.” Adding to this evidence, scientists observed that the demographic curve of human beings began to decrease over the same period megafauna entered the last stage of extinction.

More evidence for an old hypothesis

This new evidence emerged after comparing 51 temporal records of the ‘Fishtail’ tip with 269 fossils of ten megafauna species – including the American horse and the Megatherium or giant ground sloth– all dated using radiocarbon techniques, which determines the age of carbon-containing materials.

“What we found first is that populations of megafauna kept increasing until at one point – 12,900 years ago – they began to decline sharply. This coincides exactly with the moment of appearance of the fishtail tips, so we suppose that when humans obtained this new technology they began to hunt these mammals, and hence led to the decline of these populations,” explains Perez.


Fig. 2
The temporal change in the density of large mammals (a), Fishtail projectile points (b), and all archeological sites (c) described using SCPD curves. Different regions are indicated in shading colors: Andes (light blues), Pampa (light red), Patagonia (light green). X-axis represents Calibrated years BP and Y-axis the standardized summed probability. / Image: Luciano Prates e Ivan Perez


“This situation lasts for 2,000 years and ends with the simultaneous disappearance of the animals and the spearheads, which shows us that they were intimately linked,” adds Prates. In this scenario, the drop in the human demographic curve is a result the overhunting of the fauna – human populations began to reduce due to the disappearance of one of their main subsistence resources.

  • Read More: The hidden “armor” found in the skin of a giant ground sloth


The published research also includes a geographic analysis comprising of 156 spatial records of ‘fishtail’ tips and another 204 spearheads which correspond with specimens of megafauna. These specimens came from 1660 archaeological sites between 7-15 thousand years old throughout South America.

The results also support the authors’ hypothesis that the majority of the megafauna were found in the same places as the weapons. “This means that the people who hunted with this technology were located in the regions where these animals lived, which were mainly the open steppes of the pampas of Uruguay, southern Brazil and Argentina, and Patagonia,” says Prates.


This figure shows the density of megafauna in South America (left), and the density of ‘Fishtail’ points (right) / Image: Researchers courtesy


“Using all this information as a base, a product of combined paleontological and archaeological evidence, our work postulates that human beings were primarily responsible for the extinction of the megafauna.”

“However, early humans did not compulsively attack all the species present, as suggested by the North American paleontologist Paul Martin 40 years ago,” says Perez, “We suspect that people dedicated themselves to hunting only a few species, however this caused such a deep imbalance within the ecosystem that eventually, given the added climatic changes, triggered a general collapse of the entire community of large mammals.”


Mercedes Benialgo


Prates L., Perez I., Late Pleistocene South American megafaunal extinctions associated with rise of Fishtail points and human population. Nature communications. DOI:

Original article in Spanish:

The hidden “armor” found in the skin of a giant ground sloth

The hidden “armor” found in the skin of a giant ground sloth

Argentinian scientists used X-rays on a 13,000-year-old sloth skin and discovered thousands of tiny bones on the inside.

After having managed to determine the precise age of the famous mummified skin of a Mylodon (an extinct species of giant ground sloth) the same scientists continue their quest to further understand this ancient animal.  This well-preserved skin was found on a scientific expedition, led by the Museo de La Plata (UNLP) at the end of the 19th century and continues to shed some fascinating results.

The scientists applied a rare diagnostic technique in the study of paleontological remains: X-rays. The results of the analysis, which have just been published in the Journal of Morphology, allow us to infer previously unknown aspects of the biology and evolution of the huge sloth Mylodons.


giant sloth mylodon
Weighing between 1,000-2,000 kilograms (2204-4409 lbs), the mighty Mylodon reached lengths of about three meters long (10 feet). / Illustration: Nestor Toledo

The skin is 13,200 years old and is only a portion of an animal whose largest specimens reached more than one ton in weight and three meters in length. It is believed that the ideal conditions of the cave in which it was found led to its excellent degree of preservation (which includes mummified hair and other soft parts).


mummified giant sloth
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. / Photo: Nestor Toledo

The pattern of the bones

Embedded in the skin is a layer of thousands of small bones ranging from the size of a lentil to 2 centimeters in diameter. These well-ordered structures caught the attention of the study authors, who decided to X-ray it using portable equipment for veterinary use. “This feature of the skin of the giant sloths was already known about, but it was thought that these bone pieces were scattered at random, but we discovered that they are arranged according to a pattern,” says Néstor Toledo, CONICET researcher at the Faculty of Natural Sciences Museum of the National University of La Plata (FCNyM, UNLP) in Argentina.


giant sloth armor skin
This Image shows the disposition of the ossicles of the Mylodon and comparison in size with a human. | Image: CONICET


Thus, in the four radiographs taken, these tiny bones (called ossicles) – were shown to form rows or bands in some areas, and rosettes or stars in others. When looking for bibliographic references that could complement these observations, they found that, without knowing it, they applied the same technique that Wilhelm von Branco had used over a century before.

Wilhem von Branco was a German scientist who published a report on X-ray analysis in 1906.  X-ray technology had just been discovered a decade before, and he applied this new technology to different paleontological pieces, among which, coincidentally, was another Mylodon skin preserved in the Natural History Museum in Berlin.

To the great surprise of Toledo and his colleagues, von Branco had also noted the same patterns in the skin bones of the Mylodon that they were now seeing.

“By superimposing von Branco’s radiographs with ours, we came to understand that the rosette structures would be located in the area of ​​the spine and its surroundings, while the row ones would be located on the sides and near the legs.”

“With this information, we began to discuss the probable functional reasons for these positions, thinking of those bones as a kind of armor that would still enable movement,” describes Toledo.

Therefore, the skin over the parts of the body that needed greater flexibility (such as the armpits or the belly) could fold or wrinkle, while other parts benefitted from a more rigid structure. All these conjectures raised a new question: Why did these animals have such thick skin that was reinforced with these small bones?


armor skin

An actual armor?

“The strongest hypothesis regarding the function of this dermal skeleton is related to defense against other organisms: firstly, possible predators, but also individuals of the same species during combat (such as competing males) based on the behavior of some current mammals,” explains Alberto Boscaini, CONICET researcher at the Institute of Ecology, Genetics, and Evolution of Buenos Aires (IEGEBA, CONICET-UBA).

Although the first option casts some doubts as to which species would attack animals of this size, the main argument would be evolutionary in nature: the oldest records of ossicles in the skin date back to other Mylodonts of the Mylodontini group, which lived about 10 million ago and were quite a bit smaller.

“They could have been eaten by carnivorous marsupials and large birds, so having an internal shell would be a great advantage. It may be that this structure was inherited by subsequent generations, even as they increased in size,” says the expert.


ancient sloth
Artist’s rendition of a giant caiman (Purussaurus) attacking a giant ground sloth (Pseudoprepotherium)./Image by Jorge A. González


Related to the issue of evolution, another question appears, but this time it looks to the present. “In paleontology, resorting to current animals as a key to understanding those that no longer exist is very common and is known as the ‘principle of actualism’.

In this case, we can look to the only living mammal that still has bones in its skin: the armadillo, which has similar bone patterns as the sloths of the past, that is to say, the rosettes and rows of ossicles,” Boscaini describes.

Although for the researchers this could answer the purely functional questions related to the necessary rigidity and mobility in the different areas of the body, these similarities could also suggest a shared development pattern, “perhaps related to the expression of the same genes,” he points out.

Handling and cultural significance

The application of X-rays to the mummified skin was a delicate procedure that required the participation of specialized technicians to be able to use the equipment without moving it from the display case in which it is exhibited. More than a century prior, von Branco also used X-rays to examine a preserved skin but he went about it in a very different way.

To do so, he exposed the preserved “leather” to steam to soften it and then stretched it on a smooth surface on which he took X-rays. “The positive thing is that those plates have an extraordinary quality and were very useful for our study, but in truth, it is an unthinkable thing to do today: it is practically an attack on a piece that is unique and invaluable,” he explains. Leandro M. Pérez, also a CONICET researcher at the FCNyM and one of the authors of the work.


giant sloth skin armor
Leandro Pérez, one of the researchers, next to the showcase where the skin is exhibited. Photo: Courtesy of researchers.


According to Leandro, the enactment of the Argentinian Law for the Protection of Archaeological and Paleontological Heritage in 2003 was very important to prevent the manipulation of these types of remains or fossils. “The sloth skin that we have in the local museum is a real treasure: it is likely that nothing remotely similar will be found again.”

“The mummified skin has some very deep cuts and even some parts missing because in the ’70s samples were extracted for the first radiocarbon dating, a method that looks for the presence of isotopes of a certain chemical element within the sample. Nowadays, even though it is wrinkled and dehydrated, we know that it should not be modified (even though that is how we usually take X-rays) which is why in many areas the bones are superimposed on each other,” added Pérez.


-By Mercedes Benialgo, CONICET La Plata

Bibliographic references:

Nestor Toledo, Alberto Boscaini, Leandro Martín Pérez. The dermal armor of mylodontid sloths (Mammalia, Xenarthra) from Cueva del Milodon (Ultima Esperanza, Chile). Journal of Morphology. DOI:

Original text:

Oh My Dog Advances!

Oh My Dog Advances!

This month we want to share with you some exciting updates about one of our favourite sloth conservation initiatives: the ‘Oh My Dog!’ project. 

While dogs may be man’s “best friend”, they are also becoming a big problem for wildlife. In fact, with an estimated 1 billion dogs worldwide, our canine companions are predicted to become one of the biggest causes of animal extinctions in the future.

We already know that dog attacks are the second leading cause of death for wild sloths. But what can we do about it?


spay dog

The Challenge

If you visit Costa Rica, you will see dogs everywhere. While some of these animals are strays, the majority do actually have owners. There is a cultural tendency towards people allowing their dogs to roam freely during the day, and these unsupervised dogs are attacking people, other dogs, and wildlife (including sloths). Many of these dogs have also not been spayed or neutered, which results in lots of unwanted puppies further aggravating the situation. 

For the past year, we have been working with local organizations Puerto Viejo Dogs & Clinica Arroyo y Solano to spay and neuter dogs in the South Caribbean region, but we knew we had to do more to really have an impact.


Did you know that a single female dog can have on average 14 puppies per year?/Photo by Brett Cole

Organizing castration clinics in low-income areas

This year we are organizing several major castration clinics in which approximately 90 dogs will be sterilized. These clinics will take place in low-income and indigenous areas, and we aim to run a minimum of 4 per year – perhaps even more if we are able to generate additional funding. 

In order to make this happen, we arranged a meeting last week with the Mayor of Talamanca, Puerto Viejo Dogs, and the regional heads of SENASA (who are in control of domestic animals in Costa Rica). It was an incredibly important and productive meeting and is a huge step in the right direction to fulfilling this goal. 


Sarah Kennedy and Cecilia Pamich from SloCo, and Monica Moscarella from Puerto Viejo Dogs

Helping Sloths and Sea Turtles

Tortuguero is a town, and a national park, in the North Caribbean region of Costa Rica and it is also a high-risk area with a lot of unsupervised dogs. This location is a prime nesting spot for endangered sea turtles which lay their eggs on the beach every year.

There are more dogs than people in Tortuguero and the majority are free-roaming. These dogs are attacking and killing the endangered sea turtles, and also digging up the nests to eat the eggs.

Together with the local authorities, SINAC, Asociación de Voluntarios para áreas protegidas (ASVO), and the Sea Turtle Conservancy, we are working together to sterilize as many dogs in that area as possible, whilst also educating the local community.


sea turtle conservancy

The ‘Oh My Dog!’ Academy

We are also incredibly excited to have launched our first ‘Oh My Dog! Academy’ last week! We brought in professional dog trainers from San Jose to help us educate local dog owners and to prevent future attacks on wildlife. 

There is no dog training available in the South Caribbean region and as a lot of people have dogs with a high prey drive, working dogs, or large breeds, it is difficult for people to properly train these animals. 



With the help of local businesses Statshu’s Con Fusion and Casa Verde Lodge who provided us with the spaces for the course, we taught over 30 dogs last week (…and humans, because really it is the humans who need the training, not the dogs)! We will be hosting frequent academy courses throughout the year and we are confident that this is going to really help to reduce the number of dogs that are attacking sloths in the region. 

I truly believe that by working together like this we can instigate real, positive change. We are so incredibly grateful to all of those people who took the time out of their busy schedules to bring their dogs for training, and to all of our supporters who make it possible for us to run our projects every day. We couldn’t do it without you!



-Sarah Kennedy

Director of Education and Outreach

Oh My Dog! Manager