Sloth (families Megalonychidae and Bradypodidae)

I remember when I was a kid (and also still as an adult) one of the highlights of visiting the Vancouver Aquarium was spending time in the aviary. Why there was an aviary at an aquarium, I never quite figured out,  but it was still a fun place to visit. Every time my family would go there, we’d have a competition to see who could spot the sloth first. He lived in the trees, and was very difficult to see. I have fond memories of that sloth.

There are two families of sloths: two- and three-toed varieties. Two species of two-toed sloths still exist, while there are four species of three-toed sloth. All extant species live in Central or South America, and unlike their ground-dwelling or aquatic ancestors, modern sloths have moved to the trees.

A sloth hanging from a tree. The sloth's big claws aren't just useful for defence - they let the sloth hang upside down while virtually expending no energy.  Image source: http://thebiggreeniecomic.blogspot.ca/2010/07/sloth-are-green-less-haste-more-sloth.html

A sloth hanging from a tree. The sloth’s big claws aren’t just useful for defence – they let the sloth hang upside down while virtually expending no energy.
Image source: http://thebiggreeniecomic.blogspot.ca/2010/07/sloth-are-green-less-haste-more-sloth.html

Sloths weigh between 3 and 9 kg and can reach over half a metre in length, depending on the species. They have long, coarse hair that is tan to grey in colour. The hairs of the sloth’s coat are designed so that they point towards the ground when the sloth is hanging from trees, an adaptation which may help the fur shed rain. Sloth fur is also remarkable for its ability to host other species — at least two species of cyanobacteria live in sloth fur, as well as beetles, moths, fungi, and a host of other creepy crawlies. So my advice to you: don’t hug sloths, it probably isn’t very pleasant.

Sloths subsist on plant matter, mainly buds, shoots and leaves that they find in the trees. They have a number of special adaptations that allow them to process such an energy-low diet. The sloth’s multi-chambered stomach houses bacteria that help digest the leaves, a process that can take over a month to complete. Because their digestion is so slow (almost sloth-like, one might say), sloths often have food their stomachs, which can account for two-thirds of the sloth’s weight.

Leaves are not a great source of energy, so sloths try not to move unless they really need to, and maintain a low body temperature. They do come to the ground occasionally, mostly to excrete urine and faeces, an event which occurs about once a week. The sloths come to the ground and do their business, digging a hole and covering it up. The reason for this behaviour is unknown, especially as sloths are very vulnerable to predators while on the ground.

A three-toed sloth and her baby (successfully) clinging to her fur.  Image source: http://www.toptenz.net/top-10-world-records-slowness.php

A three-toed sloth and her baby (successfully) clinging to her fur.
Image source: http://www.toptenz.net/top-10-world-records-slowness.php

One possible explanation for using a toilet on the ground is that sloths rarely come into contact with each other, and the latrines provide a greater possibility of finding a mate. Once a sloth does find a mate, the mother will carry around the resulting child which clings to her fur. These poor babies have been known to fall off their mothers, but luckily they are tough and usually survive falls. Unfortunately, sloths are well named, as some mothers are far too lazy to go get the fallen baby sloth, which then dies on the forest floor.

Still, despite their bad parenting skills, sloths are pretty cute. I’m definitely going to try and find the sloth next time at the aquarium, if it’s still there. I’m a big sloth fan.

Cover image source: http://travel.nationalgeographic.com/travel/countries/costa-rica-photos/

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