New research suggests that the dodo, an extinct bird whose name has entered popular culture as a symbol of stupidity, was actually fairly smart. The work, published today in the Zoological Journal of the Linnean Society, finds that the overall size of the dodo’s brain in relation to its body size was on par with its closest living relatives: pigeons—birds whose ability to be trained implies they're no dummies.
The dodo (Raphus cucullatus) was a large, flightless bird that lived on the island of Mauritius in the Indian Ocean, where they were last seen alive in 1662. When sailors discovered the island in the late 1500s, the dodo didn't fear these new arrivals. That led to the birds being herded onto passing boats as an easy meal for passing sailors.
"Because of that behavior 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,” said Eugenia Gold, the lead author of the paper, a research associate and recent graduate of the Museum's Richard Gilder Graduate School, and an instructor in the Department of Anatomical Sciences at Stony Brook University.
Though the bird has become iconic in popular culture, most aspects of the dodo’s biology are still unknown, partly because specimens are extremely rare. To examine the brain of the dodo, Gold tracked down a well-preserved skull from the collections of London's Natural History Museum and imaged it there with high-resolution computed tomography (CT) scanning, which can produce images of the brain inferred from the shape of the skull.
In the Museum's Microscopy and Imaging Facility, Gold also CT-scanned the skulls of seven species of pigeons for comparison, while colleagues at the Natural History Museum of Denmark and National Museum of Scotland sent her the endocasts for the dodo’s closest relative, the now-extinct Rodrigues solitaire (Pezophaps solitaria). The results found that the dodo's brain was about average for its body size.
“So if you take brain size as a proxy for intelligence, dodos probably had a similar intelligence level to pigeons," Gold said. "Of course, there’s more to intelligence than just overall brain size, but this gives us a basic measure.”
While the brains of dodos might not have been small, they did reveal some unexpected surprises. The study found that both the dodo and the Rodrigues solitaire had large and differentiated olfactory bulbs, an unusual trait in birds, which depend on sight and thus usually have more heavily developed optical lobes. The authors suggest that because dodos and solitaires were ground-dwellers, they relied on smell to find food, making an oddly large olfactory lobe an asset.