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For reference, Big Bird's "Sesame Street" stands at 8 feet, 2 inches.
"Barely 500 years ago, giant, almost blind and flightless birds were smashing in the dark around the forests of Madagascar, no one expected that," said Julia Clarke, co -Leader of the study and professor at the Jackson University School of Texas. geosciences.
It was believed that these birds resembled emu and ostrich; They are also large birds unable to fly, but they are active during the day and have a good view. But this new research highlights elephant birds as being closer to kiwis – also nocturnal with poor vision. Kiwis, which are about the size of a chicken, live in New Zealand.
Because the skulls of the birds are well adjusted around their brains, the shape of the skull is correlated with the structures of the brain. Research on brain reconstruction in elephants has revealed that their optic lobes, the nerves that control sight, are incredibly small and almost absent. This is very similar to the kiwi.
"The most surprising was certainly the small size of the optical lobes of the elephant bird," said Christopher Torres, co-author of the study and PhD student. candidate at the University of Texas at Austin. "The few studies that speculated on their behavior explicitly badumed that they were active during the day, and then, once we made the connection with the night, we were blown away." That meant revisiting over 100 years of attempts to rebuild the elephant lifestyle. "
So, how did elephant birds become nocturnal?
"A night lifestyle is often an evolutionary answer, that it's too dangerous to go out during the day or what you eat comes in the evening," Torres said.
But elephant birds had no known predators and were feeding on plants.
In this case, the night is probably a trait inherited from the ancestor shared by elephant birds and kiwis. And sometimes, competition between species can cause extreme evolutions.
Researchers have identified a pattern in which these birds undergo a nocturnal phase, caused by a sensitivity to light, allowing them to see in low light conditions, said Torres. In birds that do not fly, their visual is reduced and they depend on the other senses.
They also examined the larger group of birds, including ostriches, emus, cbadowaries, rheas, kiwis, moas and tinamous, in which a relationship has developed between the development of the sense of smell and the preference of the habitat.
"The species in this group that live in the forests seem to rely on a well-developed sense of smell to help them forage in conditions where visual cues could be clogged," Torres said. .
The following mystery concerns why elephant birds have disappeared, and the problem is not solved. But scientists have clues about hunting and habitat destruction by humans, as well as climate change.
At the time, Madagascar's climate was still changing and humans had not yet reached the point where they could affect global climate change.
"Recent studies suggest that elephant birds have survived initial contact with humans for many thousands of years based on tool benchmarks observed on radiometrically dated remains," he said. Torres.
And knowing that elephant birds were nocturnal also helps explain why they could coexist with humans for so long. Other birds have not had that chance. The Moa, nine species of birds unable to fly, would have disappeared just a few centuries after the pbadage of humans in New Zealand, he said.
In the future, Torres wants to take a closer look at the strange evolutionary stories of creatures like elephant birds.
"Studying the shape of the brain is a very useful way of relating ecology – the relationship between the bird and the environment – and anatomy," Torres said. . "Discoveries like these give us a great insight into the life of these strange and misunderstood birds."
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