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A digital brain reconstruction of a recently extinct elephant bird revealed that its optic lobes were virtually absent, a trait common with the kiwi, a closely related relative, which indicates that it was nocturnal and possibly blinded. This is in contrast to the distantly related tinamous, which is active during the day and can see. Credit: C. Torres for the University of Texas at Austin.
If you met an elephant bird today, it would be hard to miss it. Measuring more than 10 feet tall, the extinct avian is the largest bird known to science. However, while you look up with wonder, it is likely that the big bird will not turn around.
According to research on brain reconstruction conducted by the University of Texas at Austin, the part of the brain of the elephant bird that was treating the vision was tiny, which indicates that it was nocturnal and maybe blind. The results were published on October 31 in the journal Acts of the Royal Society B.
A night lifestyle is a trait shared by the closest living relative of the elephant bird, the kiwi – a virtually blind New Zealand resident, and a clue that helps scientists learn about it. more on the behavior and habitat of the elephant bird, said Christopher Torres. , a PhD candidate who conducted the research.
"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."
Julia Clarke, Professor at the UT Jackson School of Geosciences and Ph.D. Torres Advisor, co-authored the study. Torres is a student in the Department of Integrative Biology of UT at the College of Natural Sciences.
The elephant birds were large, unable to fly and lived in what is today Madagascar until a mix of habitat loss and potential human interference drove them away. to their disappearance between 500 and 1000 years ago.
"Humans have lived alongside and even hunted elephant birds for thousands of years," Torres said. "But we still know almost nothing about their lives – we do not even know exactly when or why they disappeared."
Giant nocturnal elephant birds are represented digging in the ancient forests of Madagascar at night. Credit: John Maisano for the University of Texas at the Austin Jackson School of Geosciences.
Scientists had previously assumed that elephant birds looked like other large, non-flying birds, such as emus and ostrich, both active during the day and having good eyesight. But Torres and Clarke have revealed that elephant birds have distinctly different lifestyles through reconstructions of their brains.
Bird skulls wind tightly around their brains, curves and curves of the bones corresponding to brain structures. The researchers studied the skulls of two species of elephant birds. Using computed tomography data from the skulls of two elephant birds, the researchers were able to create digital reconstructions of the brain, called endocasts. In addition to elephant bird skulls, researchers have also created endocasts for close relatives of elephant birds, both live and extirpated.
In both skulls of elephant birds, the optic lobe – a bundle of brain nerves controlling the view – was very small, the structure being almost absent in larger species. The lobe had the most in common with that of a kiwi, which, according to Torres, was a "total shock" because of poor vision and nocturnal behavior of the kiwi.
"No one ever suspected that elephant birds were nocturnal," Torres said. "The few studies that speculated on their behavior explicitly asserted that they were active during the day."
Andrew Iwaniuk, an associate professor at the University of Lethbridge and expert on brain evolution in birds who did not participate in the research, said he had had a similar reaction to the results.
"I was surprised to find that the visual system is so small in a bird of this size," he said. "For a bird of this size, it is really strange to develop a night lifestyle, making it a different ecology from that of its closest relatives or any other species of bird we know."
In addition to vision, the endocasts of the olfactory bulb – the part of the brain that treats the sense of smell – have helped to better understand the habitats where elephants lived. The larger of the two species of elephant birds had a large olfactory bulb, a trait associated with forest habitat. In contrast, the smaller elephant bird species had a smaller olfactory bulb, which could indicate that he lived in the grasslands. Smaller species also appear to have a slightly brighter vision, which means that they may have been more active at dusk than at the intense darkness of the night.
"Details like these tell us not only what the life of elephant birds was like, but also what life in general in Madagascar looked like in the distant past," Clarke said. "Barely 500 years ago, giant, almost blind and flightless birds were smashing in the dark around the forests of Madagascar, no one expected that."
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More information:
Night giants: evolution of sensory ecology in elephant birds and other paleognaths deduced from digital reconstructions of the brain, Acts of the Royal Society B, rspb.royalsocietypublishing.or … .1098 / rspb.2018.1540
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