According to a new study in the Zoological Journal of the Linnean Society, an extinct bird known as the dodo (Raphus cucullatus) was in fact relatively smart.
The dodo (Raphus cucullatus) by Frederick William Frohawk, 1905.
The dodo is an extinct flightless bird that lived on the Indian Ocean island of Mauritius. It was discovered by European sailors in 1598, and was extinct by 1680.
The bird was about 1 m tall, weighed 10-23 kg, and had blue-gray plumage, a big head, a long bill, small useless wings, stout yellow legs, and a tuft of curly feathers high on its rear end.
Even though the dodo has become an example of stupidity, oddity, obsolescence, and extinction, most aspects of its biology are still unknown.
To examine the brain of the dodo, a team of researchers from Denmark and the United States imaged a well-preserved skull of the bird with high-resolution computed tomography (CT) scanning.
They also CT-scanned the skulls of eight close relatives — ranging from the extinct bird Rodrigues solitaire (Pezophaps solitaria) to the common pigeon (Columba livia).
Out of these scans, the scientists built virtual brain endocasts to determine the overall brain size as well as the size of various structures.
When comparing the size of the birds’ brains to their body sizes, they 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,” said study lead author Maria Eugenia Leone Gold, a researcher at Stony Brook University and the American Museum of Natural History.
“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,” Gold said.
Side views of brain endocasts from the dodo (left), the Rodrigues solitaire (center), and the Nicobar pigeon (right): enlarged olfactory bulbs, labeled ob, can be seen in the dodo and the solitaire. Scale bar – 15 mm. Image credit: Maria Eugenia Leone Gold et al. / American Museum of Natural History.
Both the dodo and the Rodrigues solitaire had large and differentiated olfactory bulbs, according to the scientists.
They also discovered an unusual curvature of the dodo’s semicircular canal — the balance organs located in the ear.
“Enlarged olfactory bulbs are a shared characteristic of the Raphinae and posteriorly angled semicircular canals are particular to the dodo compared with the other eight species sampled here,” Gold and co-authors said.
In general, birds depend much more on sight rather than smell to navigate through their world, and as a result, they tend to have larger optic lobes than olfactory bulbs.
“Because dodos and Rodrigues solitaires were ground-dwellers, they relied on smell to find food, which might have included fruit, small land vertebrates, and marine animals like shellfish,” the scientists said.
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Maria Eugenia Leone Gold et al. The first endocast of the extinct dodo (Raphus cucullatus) and an anatomical comparison amongst close relatives (Aves, Columbiformes). Zoological Journal of the Linnean Society, published online February 23, 2016; doi: 10.1111/zoj.12388
