Myth, Mess, and Mitochondria: How The Biggest Bird To Ever Exist Evolved And Died In Madagascar

The animal you’re facing down? An elephant bird. Once endemic to Madagascar, the species has now been extinct for 1,000 years or more – but where they came from, how they lived, and where they all went, is still something of a mystery.

The myth of the elephant bird

The earliest written records of elephant birds might not be where you expect. “Throughout the history of research into elephant birds […] the enormous eggs of aepyornithids have been proposed to be the basis of stories of avian megafauna in fictional literature,” wrote paleoecologist James Hansford in his 2018 doctoral thesis. 

For example, “[Marco] Polo describes a giant eagle type bird he personally witnessed on a trip to Madagascar ‘coming from the south’, and details the gift of an impossibly large Rukh feather to Kublai-Khan,” Hansford notes – though, he adds, “as Polo’s expeditions to Madagascar may not have occurred, this account cannot be accepted as reliable evidence of avian megafauna.”

They also may potentially be recorded – named, even – in some of the stories of Sinbad the sailor: “The second voyage describes the Rukh as a giant bird big enough to carry an elephant within its talons and its enormous eggs the size of a house,” Hansard points out, while “the fifth voyage describes the Rukh [as being] from a desert island with giant eggs on its shores.”

Of course, these are exaggerations at best: “‘An egg the size of a house’ cannot be used as an accurate description of an elephant bird egg or any animal,” Hansard writes. But it’s intriguing that only the eggs are detailed in the tales, he points out: “the lack of description of an adult elephant bird [may] indicat[e] that this narrative may have started after their extinction,” he suggests, “as their eggs remained important cultural artefacts.”

Classifying the elephant bird

So, what of a more scientific classification of the bird? Well, even here, descriptions of the elephant birds and their relatives have been – well, to use the term employed by paleobiologists Delphine Angst and Eric Buffetaut, “chaotic”. 

“The first taxonomic articles were poorly illustrated and descriptions were most often very limited,” they wrote in 2017; they were based on scrappy remains, interpreted by 19th century explorers, and the result was a collection of sometimes-conflicting, sometimes-overlapping, sometimes-downright-nonsensical species classifications. Even with more modern techniques, the picture has remained muddy, since Madagascar, with its hot, humid climate, just isn’t very conducive to DNA preservation.

Very recently, though, researchers have managed to prune the mess down to a relatively stable picture: “At the time of their extinction there were likely three species belonging to two different families,” explained Alicia Grealy, now a research projects officer at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia’s national science agency, back in 2023. “Although skeletal morphology had suggested there were more species, we think this was due to extreme differences between males and females of the same species.”

So what did they look like? Well, whoever named the elephant bird was, we admit, exaggerating – but not by much. With an estimated weight of 1,000 kilograms (2,200 pounds), the bird had only about one-third the heft of even the smallest elephant – but that’s still heavy enough to outweigh, say, four adult grizzly bears. 

They were tall, too: they “could reach a height of nearly three meters [nearly 10 feet] in normal standing position,” Angst and Buffetaut wrote. On the other hand, their wingspan was nonexistent – like their fellow ratites, their wings were tiny, vestigial, and completely useless for flight. 

Nevertheless, they “were very large birds,” Angst and Buffetaut explained, with “long legs […] and a relatively long and robust neck.” It had “a straight, conical, robust and unhooked beak,” and a tiny head – even compared to its smaller island cousins like A. hildebrandti or A. medius. Its face was relatively fragile, so it probably didn’t peck its food – rather, recent isotope analyses of ancient elephant bird eggshells suggests that they lived off a mix of shrubs, succulents, and grasses.

That latter fact must have been cold comfort for the animals it shared its island home with, since, being most likely nocturnal and virtually blind, this bird must have basically been an enormous chaos giant, thundering and blundering through the forest while squawking, honking, and schlurping its songs into the night.

Where did elephant birds come from?

Basically, then, the elephant bird looked similar to a rhea or emu – just quite a lot bigger and sturdier. That might make it surprising, therefore, that their closest living relative is actually neither of those. Nor is it an ostrich or a cassowary. It’s the other one – the fifth and final surviving type of ratite, and absolutely the last one you’d expect, visually speaking, to be a sister species to the gargantuan elephant bird. 

It’s this fella:

Shy, nocturnal, and only about the size of a chicken, it’s the kiwi that can boast the closest genetic connection to the elephant bird. It’s a result that “was about as unexpected as you could get,” Kieren Mitchell, then a PhD candidate at the University of Adelaide’s Australian Centre for Ancient DNA (ACAD) and coauthor of the 2014 paper that discovered the relationship, said at the time – and not just because of the birds’ physical differences. 

“New Zealand and Madagascar were only ever distantly physically joined via Antarctica and Australia,” Mitchell pointed out, “so this result shows the ratites must have dispersed around the world by flight.” 

But both species are flightless – in fact, that’s almost a defining characteristic of ratites as a group. So, what gives?

Well, the answer is not only an explanation of how elephant birds and kiwis ended up so far apart geographically, but also why they’re on such opposite ends of the size spectrum. It all goes back to Chicxulub, and the (relatively) small period of time in between non-avian dinosaurs becoming extinct and mammals moving in on their ecological niches – the era known to paleontologists as “it’s bird time babey!!” 

Well, okay, it’s not called that – but it should be. “We think the ratites exploited that narrow window of opportunity to become large herbivores,” explained Alan Cooper, then director of ACAD and another coauthor of the 2014 paper, “but once mammals also got large, about 50 million years ago, no other bird could try that idea again unless they were on a mammal free island – like the dodo.”

In other words: some ancient ratite ancestor, not yet having lost its ability to fly, exploited the sudden lack of gigantic predatory terrifying lizards by spreading out across the world and setting down roots in places as distant as Zealandia, Africa, and even South America. It was only after that, once they’d got settled in, that they evolved to better suit their new habitats.

Going extreme

In New Zealand, where the kiwis had to battle with gigantic moas for dominance, the smart move was to shrink, hide, and take over the night – but in Madagascar, it meant the appearance of another, very different quirk of biology.

“Species are limited to the environment on an island,” explained Ana Benítez-López, a researcher at Doñana Biological Station in Spain, who in 2021 helped confirm the “island rule” of evolution. 

“The level of threat from predatory animals is much lower or non-existent,” she said. “But also limited resources are available.”

The result: species that wind up endemic to one island tend to become either much smaller or much larger than their mainland relatives. It’s the reason for pygmy hippos and giant tortoises; for the nightmarishly-named giant hissing cockroach and the seemingly oxymoronic pygmy mammoth.

And for elephant birds, it happened not once, but twice: “they split from a common ancestor […] around 30 million years ago,” explained Grealy. “At this time, populations of small elephant birds may have adapted to a changing climate, eventually becoming different species – some remaining small and others becoming quite large.”

“But more recently, a second split happened among the larger of the elephant birds, which coincided with another period of climate change around 1.5 million years ago, leading to the evolution of an even larger species,” she continued. “Between this time and their extinction […] Aepyornis maximus doubled in size.” 

Which raises an interesting question…

Where did all the elephant birds go?

Sad though it is to admit, the world no longer boasts a species of real-life Big Bird – so where did they go?

Well, the truth is, we’re not exactly sure. There’s some evidence of human predation, for sure: researchers found bones with telltale cut marks in them back in 2018, a smoking gun if ever there was one. But weirdly, while confirming that humans did indeed hunt and eat elephant birds, this discovery also kind of proved the opposite – that our species may not have been quite as destructive to theirs as you might assume.

“We already [knew] that Madagascar’s megafauna – elephant birds, hippos, giant tortoises and giant lemurs – became extinct less than 1,000 years ago,” explained Hansford, then a paleoecologist at ZSL’s Institute of Zoology and lead researcher on the team who made the discovery, at the time. 

But the chopped bones they had found predated that by an order of magnitude – predating even the previously-assumed arrival date of humans to Madagascar. “Humans seem to have coexisted with elephant birds and other now-extinct species for over 9,000 years,” Hansford said, “apparently with limited negative impact on biodiversity for most of this period.”

“Our research […] demonstrates that a radically different extinction theory is required to understand the huge biodiversity loss that has occurred on the island,” he added – with the new perspective on elephant birds’ survival alongside humans “offer[ing] new insights for conservation today.”