Not only has the dodo become a byword for obsolescence it has also become something of a symbol of stupidity. But while it is undoubtedly extinct, scientists now think that it was pretty smart, at least as far as birds go.
The overall size of the dodo's brain in relation to its body size was on par with its closest living relative, the pigeon, a bird known for at least moderate intelligence.
The researchers also discovered that the dodo had an enlarged olfactory bulb – the part of the brain responsible for smelling – unusual in birds, which usually concentrate their brainpower into developing exceptional eyesight.
The dodo (Raphus cucullatus) was a large, flightless bird that lived on the island of Mauritius in the Indian Ocean.
"When the island was discovered in the late 1500s, the dodos living there had no fear of humans and they were herded onto boats and used as fresh meat for sailors," says the American Museum of Natural History's Eugenia Gold, the lead author of the paper published in the Zoological Journal of the Linnean Society.
"Because of that behaviour and invasive species that were introduced to the island, they disappeared in less than 100 years after humans arrived.
"Today, they are almost exclusively known for becoming extinct, and I think that's why we've given them this reputation of being dumb."
Until now we have known almost nothing of the biology of the birds – live specimens are, by definition, non-existent and the animals were wiped out before any reliable system of natural history collections had been developed.
But Gold managed to find one well-preserved skull from the collections of the Natural History Museum, London, and imaged it with high-resolution computed tomography (CT) scanning.
She also CT-scanned the skulls of seven species of pigeon to determine the overall brain size as well as the size of various structures of both pigeons and dodo.
The Natural History Museum of Denmark and National Museum of Scotland provided her with an endocast for the dodo's closest relative, the (also) extinct island-dwelling bird Rodrigues solitaire (Pezophaps solitaria).
When comparing the size of the birds' brains to their body sizes, Gold and collaborators found that the dodo was "right on the line".
"It's not impressively large or impressively small – it's exactly the size you would predict it to be for its body size," Gold said.
"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."
The study also revealed that both the dodo and the Rodrigues solitaire had large and differentiated olfactory bulbs.
The authors suggest that, because dodos and solitaires were ground-dwellers, they relied on smell to find food, which might have included fruit, small land vertebrates, and marine animals like shellfish.
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