This week we celebrated the 8th birthday of our resident slow coach Sid, so I thought we would delve into the realms of everyone’s favourite lazy tree dweller, the sloth.
There are 6 different species of sloth found across Central and South America:
- Pygmy three-toed sloth (Bradypus pygmaeus)
- Maned sloth (Bradypus torquatus)
- Pale-throated sloth (Bradypus tridactylus)
- Brown-throated sloth (Bradypus variegatus)
- Linnaeus’s two-toed sloth (Choloepus didactylus)
- Hoffman’s two-toed sloth (Choloepus hoffmanni)
Of these, the pygmy three-toed sloth is classed as critically endangered and the maned sloth is vulnerable whereas all the other subspecies are considered ‘least concern’ which is great news for Sid.
Ancient Sloths
Millions of years ago, just after the dinosaurs, elephant sized sloths (Megatherium) walked the earth. These 6-metre-high Giant Ground Sloths used their massive claws to pull down branches to munch on the best leaves.
They had a robust skeleton with a thick broad tail, mostly thought to have walked on all fours although they were also capable of moving bipedally as well. Studies show that this gigantic creature was thought to be mostly hairless like the elephants of today which made them quite susceptible to overheating.
It is thanks to the large stomach and digestive systems of the Giant Sloth that we have avocados today- they were one of the few animals that would eat the avocado stone whole and dispersed the seeds far and wide.
These guys went extinct around 12,000 years ago during the Quaternary extinction event, which also claimed most other large mammals in the New World. The extinction coincides with the settlement of the Americas, and a kill site where a Giant Sloth was slaughtered and butchered is known, suggesting that hunting could have caused its extinction.
All tree sloths we know today, evolved from these Giant Ground Sloths. There is also even evidence that there was once a marine sloth that fed on seaweed and sea grass in the shallow waters.
Photo credit: en:User:Ballista
Modern sloths
Today however, sloths are much less intimidating and quite a bit smaller. They can reach up 2.5 feet and weigh around 5-8kg, around the size of a small dog. They have course fur and long claws for hanging onto branches. Sloths are split into two categories: two toed and three toed sloths. Ironically, all sloths actually have three toes on their back feet but the difference is noted on their front feet. Sid is a Linnaeus’s two-toed (or should that be two-fingered?) sloth.
So what is a sloth?
Although Sid is looked after by the Primate team here at Wingham, all sloths fit into the category of mammals and have their own superorder, Xenarthra and the order Pilosa, with a family tree that includes anteaters and armadillos. So, Sid is pretty at home with his house mate Terry the Tamandua (an arboreal anteater) and his neighbour Jose, the three-banded armadillo.
All species of sloth are found across Central America and northern South America in the canopy layer of the rainforest. They spend their days curled up, hanging around and pretty much doing everything upside down including eating, sleeping, fighting, mating, and even giving birth. Sloths will spend up to 90% of their life hanging upside and so have some important adaptations to help with this.
Firstly, their 10cm long claws act like hooks to give them excellent grip on the tree branches, their grip is so strong that sloths have even been found dead but still hanging onto branches! A sloth’s internal organs are also attached to his rib cage which means when he is upside down, there is no weight baring down on his lungs meaning he can breathe freely.
Next time you see Sid, check out his hair. He has a lovely central parting of hair on his tummy which grows upwards towards his back, his face hair also points upwards which means that during a rainstorm, the water will just run off his body and dry him out quicker, stopping him from getting too cold.
But what does a sloth do?
They are most famous for doing not a lot really! Sloths will spend 15-20 hours asleep a day! And when they are on the move, everything is slowed right down. They have a very low-calorie diet consisting mainly of leaves and a little fruit (Sid is particularly partial to willow leaves and a cheeky grape) which means their metabolism is very very slow. In fact, sloths have the lowest metabolic rate of any mammal, this is the reason they move so super slowly, they need to conserve their energy and don’t wander far from their home range.
Having said this, the sloth’s incredibly strong arms help them to be fantastic swimmers and they can move three times faster in water than on land! They’ll use a doggy paddle style stroke to cross rivers in search of a mate or a new home, they may even wait for the forest to flood before dropping out the trees into the water and have even been known to hold their breath under water for 40 minutes!! Three-toed sloths actually have two extra vertebrae than any other mammal in their necks to allow them to turn their heads 270° to keep their nose above water and they are able to slow their heart rate right down to conserve even more energy when swimming.
Pooping
Due to their slow metabolism (it takes a sloth roughly 30 days to digest a single leaf!), sloths only need to go to the loo around once a week and it’s probably one of the most dangerous things they do. In fact, almost half of sloths die when doing a poo.
They will climb down a tree right to floor, dig a small hole and poo up to a third of their body weight before slowly making their way back up the tree for a rest. However, when they are on the forest floor, their long claws make it difficult for them to walk far and they will only manage to cover around 1 foot (30cm) per minute, leaving themselves open for predation from ocelots, jaguars and snakes who may be passing by looking for an easy meal. No one is entirely sure why the sloths risk their lives like this but the most considered explanation is for reproduction and communication.
Green sloths?
When asked to picture a sloth in your mind, you would probably paint them with a brown coat, maybe varying to a dark blonde colour but it is possible to catch a glimpse of a green coloured sloth in the Amazon! The sloth’s hair is long and course and contains a number of grooves in each hair which increase in number with the age of the animal.
These grooves make excellent habitats for various organisms such as moths, beetles, fungi, and algae. When sloths go for a swim, they pick up algae which grows on their fur. The sloth provides the algae with shelter and water while, in return, the algae turns them a nice shade of green creating the perfect camouflage as well as extra nutrients through their skin, a wonderful example of a symbiotic relationship.
Sloths are unable to regulate their own body temperatures and depend on the environment to do this for them. If the temperature gets too low, their body temperature will drop and the gut bacteria and microbes in the stomach will die meaning the sloth will not be able to digest the food in its tummy. The sloth will continue to eat the same number of leaves but without the ability to process the food, they will often die of starvation, even though their stomach is full.
All the little things we already know about what we can do at home to help prevent climate change can have a positive impact on the sloths too. Walking instead of driving, eating less meat, recycling etc can all help reduce the effects of climate change and help the sloths stay warm.
If you would like to learn more about sloths why not join us on our unique sloth encounter?
Until next time, take it easy, take it slow, be more sloth.
