Megatherium: Burrowing Monster Sloths
There are a lot of famous big extinct mammals – mammoths, saber-tooth tigers etc. However, one massive extinct mammal that doesn’t get anywhere near enough love is the Megatherium. It’s was a sloth, but it was about 6 meters tall and weighed around 4 tonnes, larger than a modern-day elephant. However, despite its massive size, it actually spent a lot of time burrowing, creating enormous underground tunnel networks that still exist today. Let’s dive in, to the weird and wonderful, Megatherium.
Megatherium: An introduction
The Megatherium was a giant extinct species of sloth that lived in South America up to about 10,000 years ago. It was massive, about 6 meters long and weighed 4 tonnes, slightly larger than a modern-day elephant. The only land mammals we know that would have been bigger were a couple of species of mammoth. It was truly enormous.
Megatherium was a ground sloth. There are no surviving species of ground sloths, all the sloths that are around today instead hang out in trees. Ground sloths were halfway between a sloth and a mole, they had large claws like a sloth, which instead of hanging from trees, they used to dig burrows.
Like all other sloths, Megatherium was a herbivore. It wandered about grasslands on its hind legs (like an anteater – to keep its front claws sharp), eating whatever it could find on the ground. Then when it came across a tree, it would stand up on its hind legs and pull down branches eating most of the vegetation of the tree in one go. It would have been quite a sight.
Like a lot of the giant land mammals, Megatherium went extinct surprisingly recently. Megatherium was still around up to 10,000 years ago, so the same time the first cities and written languages were created (see our timeline here). There are a few specimens that might even suggest it was around up to 7,000 years ago, so almost at the time the Egyptian pyramids were built.
It is likely that it went extinct mostly due to humans hunting it. Large numbers of Megatherium bones have turned up near human settlements, often with cut marks that suggest the animal was butchered. There are even a few sites where it looks like humans hunted and killed Megatherium by trapping them in a gulley, just like we did mammoths and other large mammals.
Megatherium: The burrows
The coolest thing about Megatherium, is almost certainly its burrows. Like moles, wombats and even some bears, Megatherium spent a significant amount of time underground.
When the Megatherium burrows were first discovered, they were a complete mystery. Geologists came across several large cave networks in the 1930s in parts of the Amazon rainforest. However, there didn’t seem to be any natural explanation for these cave networks – they weren’t near any sources of water and didn’t seem to be associated with any geological activity. Some assumed they were structures of an ancient civilization or caves made by early human ancestors, but no-one gave them that much thought.
The first paper identifying the true origin of these burrows was only released in 2010. A geologist Amilcar Adamy started by investigating a particularly large network of the tunnels in the Amazon. Over time, he discovered more and more of these tunnels, which often extend for over 100 meters and are 2 meters high and 4 meters wide – some even have their own separate chambers that randomly branch off at different points. They were truly immense, it just wasn’t plausible that any humans created with our level of technology 10,000 years ago.
Once Adamy observed large claw marks in some particularly well-preserved chambers, it clicked that these were probably the burrows of very large ancient creatures. After further investigation, hundreds more of these ‘paleoburrows’ created by different animals of different sizes was discovered.
It’s a very obvious answer now looking back on it. Of the mammals alive today, around 3.5% spend almost all their time underground. And about half of mammals spend at least some time in burrows. It’s very likely that this was true a couple of thousand years ago as well. And a lot of the animals that were around 10,000 years ago were much bigger than their modern equivalents. So it stands to reason that there would be a whole bunch of surviving massive burrows of extinct land creatures.
After the concept was established, another research surveyed a 45-mile stretch of highway construction near the city of Porto Alegre and identified paleoburrows in more than 70 percent of road cuts. Most of them were filled in and much smaller, but they’re still very distinctive, standing out as large dark knots the surrounding lighter soil. There are probably millions of paleoburrows all across the world created by different creatures at different times, some maybe even being reused by modern species like bears and wombats.
It’s not really known why a massive sloth would feel the need to burrow underground. Generally, smaller mammals do it to escape predators or keep warm. However with the size of Megatherium, those things were unlikely to be issues. It’s likely that a family of Megatherium would live in these burrows, extending them over generations. Maybe to protect their offspring? A lot more research is needed to answer these questions.
Megafauna: Humanity’s first victim?
It’s great to revel in the glory of earth’s creatures. However, it always gets a bit awkward when you find out why so many of them went extinct. It’s almost always due to humans and hunting.
Now in the 21st century, almost everyone has some appreciation of the effect humans are having on the planet. However, we still tend to focus on the most recent years – climate change, pollution, global warming etc. And that’s fair enough – those things are the most important. More than half of all CO2 emissions released by human civilization have been released since the 1980s.
However, humans have been fundamentally changed the landscape for millions of years. There was a period of time where almost the entirety of the Earth’s land arable land was covered in forests. The cleared fields and grasslands alongside highways are entirely manmade. There used to be lions on every continent until we wiped them out. The world was full of so many wonderous creatures, particularly large mammals, mammoths, enormous aurochs, giant 3-metre tall birds in Madagascar, gorilla sized lemurs all of which have gone extinct in the last few thousand years due to humans. This trend has gotten even worse since the industrial revolution with millions of species dying out – in fact most scientists consider us to be entering the sixth great extinction event, comparable to the meteor that wiped out the dinosaurs and 80% of life on Earth.
Obviously it’s not really sensible to feel guilt or responsibility for extinctions caused by humans millennia ago. However, it is worth baring in mind, when considering our effect on the environment. We like to consider these problems are intractable and impossible, as if there is nothing us little old humans can do to reshape the planet. This is not true. Humans have been the dominant global force shaping our environment for thousands of years. Anything that happens to the planet, is our responsibility. We should remember that.
