Gastrointestinal Parasites in Wild Sloths| Published Research
If you were to picture a sloth’s life in the rainforest canopy, “parasites” might not be the first thing that comes to mind. But sloths are miniature ecosystems: their coats host entire communities of moths, beetles, and green algae, a living camouflage that benefits both the sloth and its tiny passengers.
But while these organisms are harmless (and even helpful), they’re often mistaken for parasites. Real external parasites, like ticks and mites, do affect sloths and are covered in a separate blog we wrote here. But this time, we’re going deeper into the gut.
New Paper Published in Open Access
We’re thrilled to share the results of a newly published scientific study, “Host specificity of gastrointestinal parasites in free-ranging sloths from Costa Rica”, and the first of its kind to compare the gastrointestinal parasites of wild two-fingered and three-fingered sloths living in both primary forests and urban habitats.
Representing SloCo, Dr. Rebecca Cliffe and José Guzmán García collaborated with the lead author of the paper, Ezequiel Vanderhoeven from Brown University, to carry out the fieldwork in Costa Rica, collecting sloth feces with the help of our amazing sloth scat detection dog, Keysha. Samples came from the pristine rainforest of La Selva Biological Station and from forest fragments and urban patches around the South Caribbean, where sloths live just meters from human activity.
So, what was discovered in all that sloth poop?
Quite a lot, actually!
Using a microscope and some classic parasitology techniques, the team identified eight different types of gastrointestinal parasites across just 38 fecal samples. That number matches the total recorded in the scientific literature for sloths over the last 100 years, meaning that in one short field season, we doubled our understanding of these mysterious organisms.
But that wasn’t the only surprise.
Even though two-fingered (Choloepus hoffmanni) and three-fingered (Bradypus variegatus) sloths often live side by side, even in the same trees, they didn’t share a single parasite. Not one. The parasite communities were completely different between species, no matter where the sloths lived.
This means host identity plays a far bigger role than habitat regarding who’s living inside whom. In fact, some of the parasites found in primary forest sloths haven’t been described in science before. They could be entirely new species.
Hoffmann’s two-fingered sloths living in pristine primary forest had twice as many parasite types as those in urban habitats. While that might sound alarming, it actually reflects something important: healthy, intact ecosystems often support richer parasite communities.
Urban Parasites versus Jungle Parasites
The following chart shows the average number of different gastrointestinal parasite species (called parasite richness) found in the two species of wild sloths living in either urban areas or undisturbed primary forests.
While no statistically significant differences were found between species or habitat types overall, there was a marginal trend suggesting that two-fingered sloths living in primary forest host a greater diversity of parasites. This could mean that healthier, undisturbed ecosystems support a richer parasite community, which is actually a sign of balanced biodiversity.
Conservation Implications
And while most people associate parasites with illness, it’s not always so simple. Some can cause harm, others may be harmless passengers, and in rare cases, they might even be helpful. But here’s what we do know: sloths are already facing enough challenges, habitat loss, electrocutions, road collisions, and the last thing they need is added pressure from undiagnosed infections. Understanding what’s happening inside their bodies is critical for conservation and improving veterinary care.
These results are just the beginning. We still don’t know how sloths acquire many of these parasites, especially the ones that require intermediate hosts like beetles or mites. Do sloths ingest them accidentally while eating leaves? Could the insects that live in sloth fur play a role in transmission?
The more we learn about sloths, the more questions we have. But every answer brings us one step closer to keeping these animals healthy, wild, and thriving in their rainforest homes.
Collaborative Science
This research was a collaborative effort between scientists, universities, and institutions from the United States, Costa Rica, and Argentina, bringing together field expertise, laboratory analysis, and international cooperation to better understand sloth health and conservation.
The paper is published open access and free for everyone to read, because scientific discovery should never be gatekept; knowledge belongs to all of us.
Thank you to everyone who supports sloth research and conservation projects, whether by donating, sharing our work, or simply following along with curiosity. You make this science possible.
