Do sloths have tails?

It’s hard to tell under all that shaggy, mossy, moth-riddled, upside-down growing fur, but lurking at the bottom of every sloth is a cute little tail!

Three toed sloth tails vs Two toed sloth tails

Our three fingered friends have short tails of about 6-7cm (about 2-3 inches). 

three toed sloth skeleton
Chris Dodds [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)]
Two fingered sloths have even littler tails – they’re only 1.5cm – 3cm long (which is only up to just over an inch).

two toed sloth skeleton
By Cliff from I now live in Arlington, VA (Outside Washington DC), USA – Two-Toed Sloth (Choloepus hoffmanni)Uploaded by berichard, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=7607021

Why do sloths have tails?

It’s not like they wag them when they’re happy, or swish them when they’re cross. They don’t even have the energy to use them to swat annoying insects away (not that they’d be much use – they’re too small!). So why do sloths have tails?

I have read that they use their tails to dig holes in the ground to poop. But I haven’t seen any evidence of that, and I wonder if it’s really true.

So perhaps it’s just a hangover from their giant sloth days. Sloths’ ancestors, the giant ground sloths, had massive tails (they had massive everything actually) and they used to use their tails kind of like a third leg – to prop them up like a tripod.

Sloths have obviously evolved very much away from the giant sloth – but maybe their little tails are just a reminder of their long distant past.

skeleton of giant sloth tail
Giant sloth tail

 

 


Why are sloths slow?

You can be pretty sure that the first word that comes to most people’s minds when they think of sloths is S L O W.

And that’s for a good reason. Three toed sloths are indeed the slowest mammal on earth.

But sadly, in this day and age of super speed and fast paced everything, being slow doesn’t get you much respect. In fact people tend to equate slowness with stupidity.

Sloths may be very slow, but they are very far from stupid. Their slowness has a purpose, and indeed it has helped sloths to survive for millions of years!

So, instead of equating sloths with the word slow, let’s change our thinking. From now on I suggest that when we think of sloths, we think of this word:

The Cambridge definition of the word stealthy
The Cambridge Dictionary definition of the word stealthy

It makes sense doesn’t it? Sloths meet every criteria of the definition. And, stealth is cool.

Ninjas are stealthy. Ninjas are way cool.  So are sloths.

Why are sloths so slow stealthy?

Survival strategy

Fast animals like the cheetah get to be part of the cool-crowd because they are fast. Very fast.

They can run alright. They’ve evolved to be capable of short bursts of great speed, but the fact is that they lose about half of their kills to hyenas because they can’t risk getting hurt. In other words – they’re fast but not very strong.

Sloths, on the other hand, are actually really strong. Could you hang upside down from a tree for long? Me either. Sloths do it all day every day. Even though they have about 30% less muscle mass than other mammals their size, their muscles are made of special ‘low-twitch’ fibers that give them lots of strength without using a lot of energy.

No one’s perfect of course, and the cheetah is still awesome – I’m not trying to diss the cheetah. I’m just saying we need to look at the whole picture. Cheetahs are incredibly fast but they’re not very strong, and they need to work very hard for their meals.

Sloths, on the other hand, are very slow. But they don’t have to worry about hurting themselves when they’re on the hunt for their next feed. They maybe just have to rotate their neck ever so slightly and pull that tasty looking leaf of the vine.

Slowly.

And stealthily.

Diet

The sloth’s diet has a lot to do with the sloth’s speed.

As you know, sloths live on leaves, flowers and stalks. These tasty treats are actually pretty hard to digest, so sloths have developed a stomach that has four chambers. This helps them to break down the tough fibre and toxins in the leaves. But it takes about a month to digest each leaf.

This means that about 30% of the sloth’s body weight is fermenting leaves (which partly explains why they’re such good swimmers – they’re basically a fur ball of gas and this helps them to float).

Now, vegan  humans often cop a lot of flak for not having enough nutrition in their diet. Just think about the sloth’s diet for a minute!  Leaves and flowers don’t have a great deal of nutritional value, so sloths have evolved to use as little energy as possible.

Metabolism

A slow metabolism uses less energy than a fast one. And so sloths turn their food into energy at a very slow rate. In fact three toed sloths have the slowest metabolic rate of any mammal.

Scientists are discovering that their metabolism is actually pretty unique, as it seems they can temporarily suppress their metabolism when temperatures get too high (and they’re the only mammal known to do this).

Predators

Sloths have evolved alongside predators such as the harpy eagle. Harpy eagles are about as sharp-eyed as you can get and can detect the tiniest movements- so it’s actually in the sloth’s best interests to be as slow as possible. It’s harder for the harpy eagle, or big cats,  to see a slow moving sloth than another animal who is moving quickly.

Another benefit of living solely on leaves and flowers is that you don’t have to go looking for your food. Animals that have to hunt or forage for their meals regularly have to move out of their safe homes to do so, and therefore put themselves at risk of being detected by their predators. Sloths just hang out in the tree tops and slowly munch a leaf or two each day – clever! (and stealthy).

Want to learn more?

Lucy Cooke is a zoologist and an expert on sloths. Check out her very entertaining TED talk and learn more about why sloths are the masters of stealth.

If you like Lucy’s work, check out her books available on Amazon.

Please note that these are affiliate links. If you click through and make a purchase, I may receive a commission (at no additional cost to you). Thanks for your support!

cover of lucy cooke book

life in the slow lane book about sloths by lucy cooke

original sloths calendar cover 2020

power of sloth lucy cooke book

Pygmy Three Toed Sloth: Bradypus pygmaeus

pygmy three toed sloth in a tree

The Pygmy Three Toed Sloth was only quite recently declared to be a new species.

In 2001 scientists made this decision, mainly because the pygmy sloth is such a little cutie – with little being the operative word.

How big are pygmy sloths?

Pygmy sloths are about 40% smaller and lighter than their sister species, the Brown Throated Sloth. They are also approximately 15% shorter.

Their length is 48 – 53 cm, and they weigh between 2.5kg – 3.5kg. So teeny!!

Where do pygmy sloths live?

The only place in the world that you will find pygmy three toed sloths is on a little island called Isla Escudo de Veraguas. It is the furthest outlying island in the Bocas del Toro archipelago, which is a chain of islands that was separated from Panama, due to rising sea levels, about 9000 years ago.

Isla Escudo de Veraguas is only 4.3 square kms in area (1.7 sq miles)

The other islands in the Bocas del Toro archipelago are home to sloths who are also smaller than average. But it’s only on Isla Escudo de Veraguas that the sloths have been deemed sufficiently small to be classified as a separate species.

This island is also home to species of hummingbirds and bats, that can be found nowhere else.

Up until recently, it was thought that the pygmy three toed sloths only lived on the red mangroves on the outer edges of the island. However, a biologist named Bryson Voirin placed radio collars on 10 sloths in mangroves and then tracked them for a period of three years. 3 of the sloths stayed in the mangroves. 5 moved out of the mangroves and hung out in some other tree species at the mangroves’ edge. 4 adventurous pygmys travelled as far as 200 meters inland. Quite a distance if you’re a tiny little slow moving sloth!

What lives on pygmy sloths?

A pygmy sloth’s coat is home to just one type of green algae, the Tricophilus species. This algae gives the little pygmy a nice green tinge, which comes in handy as a camouflage.

But it is also home to almost 40 other creatures! This is more than any other species of sloth has crawling around in its fur.

What do pygmy three toed sloths eat?

Pygmy three toed sloths eat the leaves of the red mangrove trees (Rhizophora mangle). No other sloths eat this kind of leaf.

The red mangrove leaf is not great, nutritionally speaking, and it’s also quite coarse.

What do pygmy sloths do?

The pygmy three toed sloth lives in trees, and spends about 15-20 hours a day hanging around in them.

On the ground, they’re realllllly slow. Clocking in at 0.24km hour, they’re one of the slowest animals in the world.

Put them in water however, and boy do they go!!! (Not really, but they are about three times faster in water). Pygmy sloths do seem to like to swim more than any other sloth, and they’re the only sloths that swim in salt water. Roughly a third of a sloth’s body mass is the contents of its stomach. Because leaves generate quite a lot of gas while they’re being digested, sloths are actually a bit like a pool floatie – the air inside them helps them to be bouyant!

Are pygmy three toed sloths really different to their bigger cousins?

Some researchers believe that pygmy sloths are really just a smaller version of brown-throated three toed sloths.

Are pygmy sloths endangered?

In 2012, only 79 pygmy three toed sloths were found living on Isla Escudo de Veraguas. This has resulted in them being listed as critically endangered. The majority of these 79 sloths were found living in the mangroves at the edge of the island. It is hoped that there are actually more living in the forests further inland, where they are much harder to see and track. Due to the difficulties involved in finding animals in dense rainforests, biologist Bryson Voiring actually estimates that the population is more likely to be between 500 to 1500. Even so, this is still an extremely small number for a whole species of animal.

Living an isolated existence on a little island has resulted in inbreeding, which means the genetic diversity of the pygmy three toed sloth is ever decreasing.

Tourism development is also a threat to this species. There have been proposals to develop a marina, casion, hotel and airstrip on the island.

Although no people actually live on Isla Escudo de Veraguas, indigenous people from Panama often camp there to fish. They cut down trees for their huts and firewood, and also eat sloths when they don’t catch enough fish. As mangrove trees are cut down, gaps in the canopy appear. This means the sloths have to travel on the ground more often and this puts them at risk of being eaten by feral cats and other predators. Although the Panamanian government has listed Isla Escudo de Veraguas as a National Park, it doesn’t enforce laws about cutting down the mangroves.  Biologist Bryson Voirin believes that unless this changes, and the pygmy three toed sloth is given some more protection, they may only have a few years left on this planet.



Recommended Reading

Mongabay interview with Bryson Voirin

Keeping pygmy sloths afloat

Wikipedia

More endangered pygmy sloths in Panama than previously estimated

The Brown Throated Sloth (Bradypus variegatus)

brown throated sloth in a tree
Photo Credit

Appearance

Coat

With its adorable super-hero style mask over its eyes, the Brown Throated Sloth is probably the one that most people think of when you tell them how much you LOVE sloths.

They have greyish brown to beige fur on their body, with darker brown fur on their throat, forehead and the sides of their face.

Their face is paler, with the well recognised dark strip running accross their eyes.

They have very cool haircuts. Their hair tends to form a fringe across their foreheads.

Males have an interesteing patch of short orange fur with a black strip and spots on their upper back. This is called a speculum. Females have long back hair with spots and stripes, but no orange colorings for the poor ladies.

The markings on their back are unique to each sloth, a bit like our fingerprints. This makes it much easier for researchers to identify individual sloths.

Their fur hangs backwards, to allow the water to run off them as they hang upside down from the trees.

Their fur is generally inhabited by a species of moth called Cryptoses choloepi (known as a sloth moth). This moth produces a fertile environment in the sloth’s coat which allows algae to grow. This can give the sloth a green tinge and a handy camouflage, but it also provides the sloth with a nutritious plant food growing right there on their back!

Arms and legs

As you can see in the picture, the Brown Throated Sloth is a three toed (or fingered) sloth. Both its forearms and hindlegs have three claws.

Their claws can grow to be 7-8 cm long on their hands, and 5 – 5.5 cm long on their feet.

Brown Throated Sloths have arms that are twice as long as their legs.

Size

Both male and female brown throated sloths grow to about 42 – 80 cm in height. Adults weigh 2.25 – 6.3 kg (again – no difference between the boys and the girls).

Their heads are small in relation to their body and their mouth is an ever-appealing smile shape.

Skeletal features

They have a stumpy tail, about 4 inches (10cm) long.

Most mammals have 7 vertebrae, but three toed sloths have 9. This allows them a much greater rotation – they can turn their neck about 270 degrees. This comes in very handy when they’re going for a swim as it allows them to keep their head out of water much more easily. It also allows them to scan for predators, like harpy eagles and jaguars, without using too much energy in moving their body position.

Brown Throated Sloths have 12 sets of ribs (24 in total).

Organs

Brown throated sloths have no gall bladder, appendix or cecum.

Habitat

Brown Throated sloths live in the neotropical ecozone of Central and South America. They can be found in Honduras, Nicaragua, Panama, Venezuela, Costa Rica, Bolivia, Ecuador, Brazil and eastern parts of Peru.

They can be found in a variety of environments. Dry forests and evergreen ones.

1200m (3,900ft) is about as high above sea level as they’ll get, but some adventurous individuals have been found up even higher.

Diet

Bradypus sloths are strict vegetarians and are pretty selective about which leaves they eat. Overall, they can eat up to 96 different types of leaves, but each individual sloth usually chooses from just 5 or 6 different tree species.

They are thought to change trees every couple of days.

Ten upper and eight lower molars, which are simple and peg like, help them slowly chew their leaves each day. They don’t have any incisors.

Behavior

Brown throated sloths sleep between 15 to 18 hours each day. They are active for only brief periods of time.

They are solitary creatures who inhabit the high canopy of the forest and only come down to the ground about once a week to visit the lavatory. They don’t travel very far in their lifetimes – their range is about 0.5 to 9 ha (1.2 to 22.2 acres). Within a typical range, a sloth might visit 40 trees but it tends to specialise in one type – perhaps even spending one fifth of its time in that type of tree.

They are capable swimmers who are active in both the day time and the night time.

Mating and Breeding

Brown throated sloths have no external genitalia.

The female lets out a loud shrill scream during mating season to attract the boys. It apparently sounds like a woman screaming – an ‘AY AY’ sound.

The life expectancy of a Brown Throated Sloth is about 30 years, and both males and females reach sexual maturity at 3 years of age.

No one knows exactly – but they think that the gestation period is about six months.

A single baby is born, and hangs on to mom for the next 8 to 12 months. Baby learns how to select the right type of tree and mom passes on her preferences for specific trees to her offspring.

Babies are weaned at about 4-5 weeks, then they start learning about leaves by licking their mom’s mouth.

After about a year, mom moves far away from her baby, but stays within her territory.

Threats and Conservation

Brown Throated Sloths are classified as least concern, but some populations are threatened by the destruction of their habitat. In the Atlantic Forest of Brazil, for example, the Brown Throated Sloths have a very low genetic diversity and are at risk from hunting. In Colombia there is a growing illegal pet trade. These amazing fringed friends are also at risk from being killed on the roads.


Recommended Reading

Brown Throated Sloth – Wikipedia

World Land Trust

Sloth Sanctuary Costa Rica