World’s biggest bird might have been as blind as a bat

The world’s biggest bird—which went extinct some 300 years ago—weighed half a ton and towered over lesser creatures in its home forests of Madagascar. Now, thanks to new evidence from skull scans, scientists think the 3.5-meter-tall elephant bird may not have been a daytime forager as previously suspected, but was instead a sightless creature of the night.

Not much is known about Madagascar’s elephant birds, whose skeletons—poorly preserved in the island’s swamps—are mostly in pieces. Until recently, scientists assumed their closest relative was the giant moa from New Zealand. They also assumed that, like the moa, elephant birds were active during the day. But recent DNA analysis has suggested the elephant bird may have an even closer cousin: the flightless, nocturnal kiwi.

To learn more about how elephant birds lived, researchers obtained skulls from two elephant bird species and measured their interiors using a computerized tomography scanner. The scans revealed that the optic lobes—which process what the eye sees—were almost nonexistent, the researchers report today in the Proceedings of the Royal Society B . That means the massive birds could barely see, the scientists say. The olfactory bulbs, the brain’s smell centers, were much larger than expected in one species and slightly larger than expected in the other—which would make sense because forest-dwelling birds tend to have better senses of smell.

The small optic lobes and the enlarged smell centers resemble the brain anatomy of the kiwi and the endangered kakapo, another nocturnal New Zealand bird. That suggests that, like the kiwi and the kakapo, elephant birds were active only at night, the scientists say. If true, such behavior could help explain how elephant birds were able to survive so long after humans invaded Madagascar.