The flightless dodo bird (Raphus cucullatus) is known for its supposed lack of survival instincts that may have somehow led to its quick extinction about 400 years ago. Add that to dodo bird hunting expeditions, and the population will surely dwindle.
Since then, the word "dodo" has been a symbol in pop culture for stupidity.
However, new research suggests that these large birds, which were once endemic to Mauritius Island, might have been quite intelligent, at least as smart as a common pigeon.
Tracking Down The Dodo Bird's Skull
Although the dodo bird has become an example of stupidity, obsolescence, oddity and extinction, some aspects of the animal's biology are still unknown.
The research team found that the part of the dodo bird's brain responsible for smelling was enlarged. This was an uncharacteristic trait for birds, which typically concentrate their brainpower for eyesight, scientists said.
To further understand the dodo bird's brain, lead author Eugenia Gold tracked down a well-preserved skull from the National History Museum in London. She imaged the skull thru high-resolution computer tomography (CT) scanning.
Gold also used CT scan to capture images of the skulls of seven species of pigeons. These species ranged from the common pigeon Columba livia to more rare varieties.
From these scans, Gold built virtual brain endocasts to determine the overall brain size and the size of different structures. Her colleagues at the National Museum of Scotland and the Natural History Museum of Denmark sent the endocast for the extinct bird's closest relative, the Rodrigues solitaire (Pezophaps solitaria), an island-dwelling bird that has also turned extinct.
Gold and her colleagues found that when comparing the proportion of the dodo bird's brain to its size, the bird was on the right 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 Gold.
If the brain size is taken as proxy for intelligence, Gold said dodos had similar intelligence level as pigeons. Pigeons have the ability to be trained, and scientists said this implies a moderate level of intelligence.
While there's more to intelligence than just brain size, Gold said this has given them basic measure.
Enlarged Olfactory Bulbs
Both the dodo bird and its cousin Rodrigues solitaire were found to have enlarged olfactory bulbs, the part of the brain that receives stimuli for smelling.
Birds typically rely on their sight rather than smell to move through the world. These birds usually have bigger optic lobes than olfactory bulbs.
Gold and her team sugges that as dodos and solitaires dwelled on land, they depended on their sense of smell to hunt food, such as small land verterbrates, fruit and marine animals like shellfish.
Additionally, the research team discovered a strange curvature in the dodo bird's semicircular canal, the balance organs in the ear. However, the team has yet to find a good hypothesis for this peculiar feature.
The Extinction Of Dodo Birds
Gold said when Mauritius Island was discovered in the late 1500s, the dodo birds living on the island were not afraid of humans.
The birds were herded into boats and were used as fresh meat for sailors. Invasive species were also introduced to the island.
Because of these factors, dodo birds disappeared in less than 100 years after humans found them. Dodo birds were allegedly last seen in 1662, although someone claimed to have seen them in 1674. A previous study featured in Nature established the birds' extinction time as 1690.
"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 Gold.
Meanwhile, Mark Norell of the American Museum of Natural History, a co-author of the study, said their study emphasizes the need for the maintenance of natural history collections.
"It is really amazing what new technologies can bring to old museum specimens," added Norell.
The team's findings are featured in the Zoological Journal of the Linnean Society.