Sometimes, when we come across a particularly cute picture or story (or I find a nice big snake/spider picture), my coworkers and I email these to each other.  Lately I’ve noticed a plethora of cute baby sloths.  Having no experience with sloths other than looking at adorable pictures, I decided to learn a little more about them.  Lucky for  you, I’m sharing.

Sloths are mammals that are known for being very slow moving, hence the name ‘sloth’.  All 6 currently living species can be found in the tree canopy, but there were ground sloths in our not too distant past.  These animals can only be found in South and Central America and are most closely related to anteaters.
The Choloepus genus consists of two species of two-toed sloths.  Interestingly, all sloths actually have three toes, but the two-toed sloths only have two fingers.  Hoffmann’s two-toed sloth (Choloepus hoffmanni) and Linnaeus’s two-toed sloth (Choloepus didactylus) are very similar and can be difficult to tell apart.  The main differences are subtle skeletal features that would be difficult to observe without some invasive  measures.  Both of these animals can range from 54 to 72 cm (21-28 in) long and weigh between 2.1 to 9 kg (4.6-20 lbs).  Hoffmann’s two-toed sloth has five subspecies:  Choloepus hoffmanni hoffmanni, Choloepus hoffmanni agustinus, Choloepus hoffmanni capitalis, Choloepus hoffmanni juruanus, and Choloepus hoffmanni pallescens.

The Bradypus genus consists of three species of three-toed sloths:  Pale-throated sloth (Bradypus tridactylus), Brown-throated sloth (Bradypus variegates), Maned sloth (Bradypus torquatus), and Pygmy three-toed sloth (Bradypus pygmaeus).  These sloths generally range between 42 to 80 cm (17-31 in) long with a weight of 2.25 to 7.5 kg (5-17 lbs).  There are seven subspecies of Brown-throated sloths: Bradypus variegatus boliviensis, Bradypus variegatus brasiliensis, Bradypus variegatus ephippiger, Bradypus variegatus gorgon, Bradypus variegatus infuscatus, Bradypus variegatus trivittatus, and Bradypus variegatus variegatus. 

Something I found quite interesting about the two sloth groups is that they actually aren’t as closely related as one might think.  In fact, two-toed sloths are more closely related to the extinct ground sloths than they are their three-toed sloth cousins.  It is believed the two living sloth species split from each other 35-40 million years ago.  Their remarkable similarities are examples of parallel evolution (remember when I mentioned this in the chimpanzee/orangutan/human debate not that long ago?).

The largest known sloth was the giant ground sloth Megatherium, which has been estimated to have weighed up to 4 tonnes with a length of 6 m (20 ft).  It was one of the largest land mammals ever known.  To give you a bit of perspective, this sloth was as big as a modern elephant.  Due to their long claws the Megatherium walked on the sides of their feet, which is how modern anteaters get around.  These enormous animals survived up until around 8,000 to 10,000 years ago.  There was a great die off of megafauna in the Americas which has been attributed to both human migration to the area as well as climate change.

Sloths are known for being slow and sleeping a lot, and in captivity they can sleep 16 to 18 hours a day.  However, by tagging wild sloths, a recent study by the scientist Dr. Rattenborg at the Max Planck Institute in Germany indicate they sleep under 10 hours a day.  It should be noted, however, that I wasn’t able to identify which species of sloth(s) he was studying.

These are slow animals, however, there’s no doubt about that.  They can move at a “fast” rate of 4 meters per minute (12 feet per minute) if escaping predators.  On the ground, however, they are much slower with a maximum speed of only 2 meters (6.5 feet) per minute (they usually only come to the ground once a week to urinate/defecate or to move to a tree they cannot reach from above).  Still, there is a beneficial reason for this.  First and foremost it is believed that since a large majority of their diet consists of leaves, which are energy-poor, sloths have evolved a slower metabolism and lower body temperature so that larger amounts of energy are not needed.  The slow movement of the sloths also attract less attention from predators.  They are so slow, in fact, that their fur can actually grow algae, which can tint their fur a green color.  That might seem a bit… out there to us.  After all, I don’t want algae growing in my hair, but for a slow moving sloth it actually helps provide camouflage, further aiding them to blend into the tree canopy.

Most of the living sloth species are classified as “least concern” which is to say they currently have a healthy population, with the exception of the maned sloth, which is classified as vulnerable, and the pygmy three-toes sloth, which is classified as critically endangered.  However, as with all animals, they are in danger from habitat destruction.  When their habitat is fragmented by roads, for example, these animals are not fast enough to avoid collisions with vehicles.  They can also be electrocuted when trying to climb power lines.  Not only can this kill the individual animal but it can also kill any babies with a mother, or leave them orphaned.  Fortunately there are some cool individuals that help sloths.  The Sloth Sanctuary in Costa Rica takes in orphaned as well as injured sloths.  Anyone that is unable to be returned to the wild stays at the Sanctuary but any adults that can be released are returned to their homes when possible.  This is a cool place to visit for anyone in or around Costa Rica.  You can tour the facilities, volunteer, or donate money and they even have a hotel where you can stay right there on Sanctuary property!

Now, go to THIS LINK to see an adorable sloth video!