The famously extinct dodo, Raphus cucullatus, disappeared about a century after humans showed up on the island of Mauritius in the Indian Ocean, and the word "dodo" became synonymous with a person that’s old-fashion, obsolete, and stupid. But now, researchers have created the world’s first internal cast of a dodo skull, and as it turns out, they may have been fairly intelligent after all. The large, flightless birds also had an enhanced sense of smell, according to findings published in the Zoological Journal of the Linnean Society this week. 

Mauritius was initially discovered by the Portuguese in 1507, but it became heavily visited by the Dutch beginning in 1598. Dodos didn’t know to be afraid of humans, so they were easily ushered onto boats as fresh meat. A few live dodos made it to Europe, but because they were confined to small spaces and fed a sailor’s diet, they ended up being portlier in their illustrations. Back home, because of overhunting, reductions in habitat from human settlement, and nest predation by introduced rats, the last dodo was seen in 1662. 

"It was really exciting to be one of the first people to see a dodo brain," American Museum of Natural History’s Eugenia Gold tells IFLScience in an email. Many aspects of the dodo's biology are still unknown, partly because of the rarity of well-preserved specimens. To examine the morphology of the bird’s braincase (or endocranium), Gold’s team turned to high-resolution X-ray computed tomography (CT) scanning, and then they compared this virtual endocast to that of eight close relatives – including a variety of pigeons as well as the flightless, island-dwelling Rodrigues solitaire, which also became extinct because of human activities. 

^{Side views of brain endocasts of the dodo (A), Rodrigues solitaire (B), and Nicobar pigeon, Caloenas nicobarica (C). The enlarged olfactory bulbs of the dodo and solitaire are labeled “ob.” The scale bar is 15 millimeters. AMNH/E. Gold}

The endocast revealed that the dodo’s brain-to-body-size ratio was similar to that of pigeons. "When I did the analysis and the dodo fell on the brain-body size line with the rest of the pigeons I sampled, it was an exciting and slightly confusing feeling. 'Wait, it's proportional? Maybe it wasn't actually that dumb?'" Gold recalls to IFLScience. 

That’s not to say the brain is impressively large, nor is it impressively small. "It's exactly the size you would predict it to be for its body size," Gold adds in a statement. "So if you take brain size as a proxy for intelligence, dodos probably had a similar intelligence level to pigeons. Of course, there's more to intelligence than just overall brain size, but this gives us a basic measure."

Additionally, the team found that the dodo and the solitaire had enlarged olfactory bulbs, the part of the brain that’s responsible for smelling. This suggests that they had an enhanced sense of smell – which is interesting because birds tend to emphasize vision over smell, Gold explains. "The dodo and solitaire must have been doing something different from the average bird." Based on sailors’ journal entries, dodos fed mostly on fruit with occasional nuts, seeds, and maybe some small vertebrates and marine invertebrates like mollusks. So perhaps the two extinct ground-dwelling island giants relied on their large olfactory bulbs to detect unspoiled fruits and small, hidden prey.