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 that 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 show 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 trees, smell, and even move like 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 different species of sloth moths, including Bradypodicola 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 become moths, they 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.


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; it is not a behavior 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 crawlies’ friends!

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