On April 20th, 2017 we learned about

Tracing the diet and activity of the massive ground sloth, Megatherium

Megatherium was a four-ton sloth that could reach up to 20 feet long, and yet we’ve only recently been able to pin down it’s role in its ecosystem. The enormous creature was one of the largest land mammals to ever live, but the details of its live just 10,000 years ago have often had to be indirectly pieced together. This isn’t to say we lack fossils of the hulking, sturdy sloth, but just that those skeletons haven’t been as definitive as one might expect. Scientists are making progress though, with new research identifying Megatherium’s diet and some of the considerable impressions it left on its Ice Age habitat.

Eating plants or prey?

Modern tree sloths are primarily plant-eaters, but some will make the occasional exception for insects or smaller critters that they can get their claws on. As an ancient ancestor to these animals, there has been some contention over Megatherium’s diet- most paleontologists were ready to call it an herbivore, but a few anatomical quirks complicated things. Swiping-friendly arm muscles were even suggested to be appropriate for aggressive, almost predatory behavior, although a lack of carnassial teeth didn’t seem to match the idea that Megatherium was out eating meat, or even scavenging carcasses on a regular basis. However, those teeth didn’t clearly align with modern herbivores either, so the issue remained unsettled.

A new study looked at Megatherium’s diet from a different angle, looking at the composition of the animal’s bones for traces the food used to grow them. The isotopes in proteins and minerals from the fossilized bones were compared against 200 living species to see what kind of diet they matched, and the answer was one that was exclusively based on plants. By taking the idea that “you are what you eat” very literally, researchers were able to show that meat was never on Megatherium’s menu.

Tracing sloths in tunnels

So what were those strong arms and claws used on? They may have clawed at foliage to clip woody stems and branches for food. They also seem to have spent some time digging, as enormous burrows in Brazil have been matched to the size, shape and orientation of their claws. While there seemed to be two main types of tunnel, the sloths’ size and maneuverability reasonably fit a number of the huge, tube-shaped tunnels.

The tunnels themselves were generally flat bottomed with the walls and ceilings being carved out as a single arch. They have been found as large as six-feet-tall by 15-feet-wide, large enough for a Megatherium sloth. Previous ideas about the tunnels have included everything from mythical monsters to ancient lava tubes, but none of hold up against the handy-work of a huge ground sloth. The one competing source of tunneling was likely another Ice Age giant, the Holmesina armadillo. It’s likely that the armadillos made the smaller tunnels, while ground sloths created the larger shelters. With around 1,500 known tunnels, these certainly weren’t secrets, but putting because the link has generally been trace fossils like claw marks, scientists have only recently felt confident about the sloths’ role in their creation.


My four-year-old asked: Could a car beat a Megatherium?

Having followed March Mammal Madness, it seems that the fighting prowess of animals is now a key reference point for my kids. At any rate, with an adult Megatherium’s weighing more than two times our Mazda 5, there don’t seem to be a lot of scenarios where our four-cylinder car could impress the four-ton sloth and be drivable afterwards.  What’s more, some of the Brazilian tunnels were made through hard, granitic rocks, meaning a modern car made with lots of light-weight plastics and crumple-zones probably wouldn’t last long against the strength of Megatheriums’ claws.

Source: The giant sloth megatherium was a vegetarian, Phys.org

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