Haast’s Eagle preyed on birds bigger than humans

That’s enough about hideously large insects. Let’s move on to hideously large birds.

Usually it’s Australia that’s famous for over-the-top dangerous fauna, but next-door New Zealand has its own contender for the crown of terrifying ancient animal.

See those running birds in the picture below?

Image: John Megahan / PLoS Biology

Those are moa, huge flightless birds. They could grow taller than 3 m. That’s not our beastie, though. This entry is about what those huge creatures (which, we remind you, are larger than human beings) are running FROM: The Haast’s eagle.

With a wingspan of up to 3 m, and claws the size of a tiger’s, this enormous bird feared exactly nothing. When your main protein source is moa, chances are you’re at the top of the food chain (this source says it was the world’s largest eagle and the top predator of its eco system).

There may have been up to 4,500 breeding pairs of these things at their peak, so when the Maori people first arrived in New Zealand, the huge predators blotting out the sun must have been a bit of a shock to them.

This source notes Maori oral tradition says it was large enough to attack children. We’ll try not to think about how they found that out.

We don’t know what kind of luck the Maori had hunting the Haast’s eagle, but they had great success hunting the moa to extinction.

With the decline of their biggest food source, not to mention shrinking forests, the Haast’s days were numbered. They went extinct around 500 years ago, dooming people in New Zealand to a life of not having to be terrified of the open sky.

Megatherium was a sloth the size of an elephant

You know tree sloths? The cute ones, with super-slow metabolisms that can barely move when they’re out of their tree, and couldn’t reasonably be expected to harm another living being? 

Well … turns out their ancestors used to live on the ground. Also, they were the size of elephants.

Image: Lady of Hats / Wikimedia Commons

Megatherium was also known as the “giant ground sloth,” which sounds like it should be a Monty Python punchline until you actually look at the size of the fossils we’ve found.

Up to 7 m long and weighing in at 2.5 tonnes, they thrived from Alaska to Patagonia until around 10,000 years ago. 

There are several theories about why they went extinct, but the top contender seem to be human impact, and an inability to adapt to climate change.

To people in the 18th and 19th centuries (and certainly to anyone happening upon such a massive skeleton), it would be easy to assume Megatherium would have been a carnivorous predator … provided you never got a good look at its jaw, which definitely looks like that of a herbivore.

In fact, although this article at Wired.com details the sort-of-science behind the carnivore theory, this paper on the beasts’ dietary habits says most people always assumed they were herbivores – although the research it cites says it might have stooped to eating carrion if plants happened to be in short supply.

Image: Robert Bruce Horsfall

Still. Although likely no real threat to the humans of the time, we have trouble wrapping out heads around having "giant" and "sloth" anywhere in the same sentence.

Paraceratherium was the largest land mammal ever

While Megatherium lived relatively close to humans' time scale, the gigantic Paraceratherium – also known as indricotherium and several other names – died out around 23 million years ago.

Image: American History of Natural History

As giants go, it’s the most giant of all, at least in mammalian terms. Standing 5.5 m at the shoulder and tipping the scales at 20 tonnes, it is the largest-ever land mammal, making mammoths look puny by comparison.

It was, of course, a herbivore. Although larger than an elephant, it was actually a kind of proto-rhinoceros, and ate leaves giraffe-like, with its long neck and, according to this source, a prehensile lower tongue.

Most people haven’t really heard about this beast, and even the ones who discovered it took a long time to even figure out what it probably looked like. Early versions made it look exactly like a rhinoceros, just three times the size and without a horn.

And of course, as a herbivore, its biggest threat to other species would likely have been through trampling, but the fossil record can’t really tell us much about its social behaviours.

We decided to put it on this list anyways, though. A gigantic prehistoric rhinoceros, harmless or not, still counts as terrifyingly huge.