Study Reveals Dodo Birds Not Stupid, as Previously Thought
Findings based on CT scans of bird skulls by a Stony Brook Anatomical Sciences researcher
A model of a dodo bird
Credit: American Museum of Natural History/C. Chesek
Stony Brook, NY, February 23, 2016 – The dodo, an extinct bird popularly recognized for its stupidity that may have led to their quick extinction, may actually have been fairly smart, at least as smart as a common pigeon. This finding is based on a study led by Eugenia Gold of Stony Brook University, and published in the Zoological Journal of the Linnean Society.
The dodo (Raphus cucullatus) was a large, flightless bird that lived on the island of Mauritius in the Indian Ocean. They were last seen in 1662. In the paper, titled “The first endocast of the extinct dodo and an anatomical comparison amongst close relatives,” Gold and colleagues find 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 a moderate level of intelligence. The researchers also discovered that the dodo had an enlarged olfactory bulb—the part of the brain responsible for smelling—an uncharacteristic trait for birds, which usually concentrate their brainpower into eyesight.
“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,” said Gold, lead author and an Instructor in the Department of Anatomical Sciences at Stony Brook University whose research centers on brain evolution between flying and non-flying birds. “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.”
Despite this reputation for stupidity, she adds, most aspects of the dodo’s biology are still unknown. This is partly because dodo specimens are extremely rare, having disappeared during the nascent stage of natural history collections.
To examine the brain of the dodo, Gold used a well-preserved skull from the collections of the Natural History Museum, London, and imaged it there with high-resolution computed tomography (CT) scanning. She used the CT scanning method at the American Museum of Natural History in New York to digitize the skull of the dodo and seven other pigeons, ranging from the common pigeon to exotic varieties. She also acquired the reconstructed brain of the dodo’s closest relative, the Rodrigues Solitare, another giant, flightless and extinct bird.
“I digitally filled in its braincase to recreate and endocast of the dodo,” explained gold. “We also performed a regression of brain volume to body size and found that the dodo has a brain completely in proportion to its body size.”
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.”
Their findings also revealed that both the dodo and the Rodrigues solitaire, which was driven to extinction in the late 1700s by human activity, had large and differentiated olfactory bulbs. 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. 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.
The researchers also discovered an unusual curvature of the dodo’s semicircular canal—the balance organs located in the ear. However, they do not have a good hypothesis for this atypical feature.
The research was supported in part by the American Museum of Natural History, the National Science Foundation, the Macaulay Family Endowment, a Marie Curie Intra European Fellowship, and the Carlsbergfondet.
Side views of brain endocasts from the dodo (A), the Rodrigues solitaire (B), and Caloenas nicobarica (C), a type of pigeon. Enlarged olfactory bulbs, labeled “ob,” can be seen in the dodo and the solitaire. The scale bar is 15 millimeters.
Credit: American Museum of Natural History/ E. Gold
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Part of the State University of New York system, Stony Brook University encompasses 200 buildings on 1,450 acres. Since welcoming its first incoming class in 1957, the University has grown tremendously, now with more than 25,000 students and 2,500 faculty. Its membership in the prestigious Association of American Universities (AAU) places Stony Brook among the top 62 research institutions in North America. U.S. News & World Report ranks Stony Brook among the top 100 universities in the nation and top 40 public universities, and Kiplinger names it one of the 35 best values in public colleges. One of four University Center campuses in the SUNY system, Stony Brook co-manages Brookhaven National Laboratory, putting it in an elite group of universities that run federal research and development laboratories. A global ranking by U.S. News & World Report places Stony Brook in the top 1 percent of institutions worldwide. It is one of only 10 universities nationwide recognized by the National Science Foundation for combining research with undergraduate education. As the largest single-site employer on Long Island, Stony Brook is a driving force of the regional economy, with an annual economic impact of $4.65 billion, generating nearly 60,000 jobs, and accounts for nearly 4 percent of all economic activity in Nassau and Suffolk counties, and roughly 7.5 percent of total jobs in Suffolk County.
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