Sloth Species: What are the different types of sloths?

Are there different species of sloths?

How many types are there?

What do people mean when they talk about species of sloths – do they mean the two and three fingered types?

Let’s have a closer look at the relationship between the different sloth species to get a better understanding of our two and three fingered friends.

Biological classification chartSloths and Evolution

You might be quite surprised to learn that two toed sloths are actually not all that closely related to three toed sloths. In fact, they’re about as closely related as you and I are to baboons.

The last time two toed and three toed sloths shared a common ground dwelling ancestor was about 30 million years ago (about the same time that us human types split from our baboon relations (although perhaps it doesn’t feel like it at some Christmas get togethers?)

It is thought that three toed sloths were the first to climb up into the trees to get a good view. The two toed sloth made its tree-change millions of years later!

What this means is that they’ve been evolving separately, although quite similarly, for all that time. This is called convergent evolution and is of quite a lot of interest to some scientists. The different number of fingers, and some differences in the way their muscles connect to their bones, is the giveaway that they are actually quite distant relatives who have each found their own special ways to live in the trees.

What’s pretty weird though, is that they both climb down from the trees, putting their lives at risk, to poop (and do the subsequent poop dance) once a week. This peculiar habit has evolved not just once, but twice. Holy sloth dung, that’s pretty amazing!

Order

So, two-toed sloths are quite distant relatives of three-toed sloths. If you have a look at the chart above, they both belong in the same order (four categories from the bottom).

The order is called Pilosa and it is one the smallest orders in the mammal class. It consists of just two suborders:

  • Folivora – sloths
  • Vermilingua – anteaters and armadillos

Fun fact – Folivora means ‘leaf eater’ and Pilosa means ‘hairy’.

Family and Genus

Moving down the rung of the biological classification chart we come to Family. Here’s where sloths get split up into five different groups. What’s terrible, though, is that three of the families are extinct. So that leaves us with two:

  • Bradypodidae – Three toed sloths are the only members of this family (and genus Bradypus)
  • Megalonychidae – This family gets split into two genus:
    • Megalonyx – an extinct genus of ground sloths.
    • Choloepus – Two toed sloths

Species

Finally we get to answer your question about how many species of sloth there are!

The two different existing sloth genus, Bradypus and Choloepus, are each split into different species.

Bradypus (Three Toed Sloth)

There are four species of three toed sloths:

  • Brown Throated Sloth (Bradypus variegatus)
  • Pale Throated Sloth (Bradypus tridactylus)
  • Maned Sloth (Bradypus torquatus)
  • Pygmy Three Toed Sloth (Bradypus pygmaeus)

Choloepus (Two Toed Sloth)

There are two species of two toed sloths:

  • Linnaeus’s Two Toed Sloth (Choloepus didactylus)
  • Hoffmann’s Two Toed Sloth (Choloepus hoffmanni)

So there you have it! If you’d like to read more about each species of sloth, then follow the links on each species name.

 

Sloth cuddling with its mom
Photo by Eric Kilby 

Differences between Two Toed and Three Toed Sloths

Clearly – a major difference is that two toed sloths have two toes, and three toed sloths have three. But it’s important to note that we are only actually talking about their ‘fingers’ here. Both types of sloth have three claws on their hind legs. This is the reason that you’ll notice people starting to refer to them as Three Fingered and Two Fingered Sloths.

Another significant difference is that two toed sloths have 5 or 6 vertebrae in their necks. Most mammals have 7. Three toed sloths have 9! This makes them able to turn their head 270 degrees, which comes in very handy when they go for a swim as they are able to keep their head out of the water easily.

Three toed sloths have small tails, but their two fingered friends have no tail at all.

Two toed sloths are larger. They’re generally 58-70 cm long and weigh 4-8 kgs. Three toed sloths are only about 45 cm long and weigh 3.5-4.5 kg.

Two toed sloths are mostly nocturnal. Three toeds are diurnal (which means they’re active in the daytime).

References

National Geographic

Two toed sloth -Wikipedia

Three toed sloth – Wikipedia

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