The Great London:
Early Birds

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 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 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.

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.

"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 Eugenia Gold, the lead author of the paper, a research associate and recent graduate of the American Museum of Natural History's Richard Gilder Graduate School, and an instructor in the Department of Anatomical Sciences at Stony Brook University. "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."

Even though the birds have become an example of oddity, obsolescence, stupidity, and extinction, and have been featured in popular stories ranging from Alice in Wonderland to Ice Age, 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 tracked down a well-preserved skull from the collections of the Natural History Museum, London, and imaged it there with high-resolution computed tomography (CT) scanning. In the American Museum of Natural History's Microscopy and Imaging Facility, she also CT-scanned the skulls of seven species of pigeons -- ranging from the common pigeon found on city streets, Columba livia, to more exotic varieties. Out of these scans, Gold built virtual brain endocasts to determine the overall brain size as well as the size of various structures. Gold's colleagues at the Natural History Museum of Denmark and National Museum of Scotland sent her the endocast for the dodo's closest relative, the 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, which recently was driven to extinction 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.

"It is really amazing what new technologies can bring to old museum specimens," said co-author Mark Norell, Macaulay Curator of Paleontology and Chair of the Division of Paleontology at the American Museum of Natural History. "This really underscores the need for the maintenance and growth of natural history collections, because who knows what's next."

The researchers also discovered an unusual curvature of the dodo's semicircular canal -- the balance organs located in the ear. But as of yet, there's not a good hypothesis for this atypical feature.

Source: American Museum of Natural History [February 23, 2016]

Medical scanners and the same software used to assess building strength after the Canterbury earthquakes, have revealed new information about the diet and dining preferences of New Zealand's extinct moa.

Researchers from Canterbury Museum, the University of Auckland, Finders University and the Universities of New England (Australia) and New South Wales have discovered that the nine species of moa were able to co-exist because differences in the structure and strength of each species' skull and bills were influenced by, or dictated by, diet.

The findings are published today in the journal >Proceedings of the Royal Society, in London.

Co-author, Dr Peter Johnston from the University of Auckland's Anatomy and Medical Imaging department, made MRI scans of the mummified moa remains to allow accurate models to be made for the research.

The moa, which roamed New Zealand until the 15th century, were herbivores and some of the largest birds to have ever existed. The largest species, the South Island Giant moa, weighed up to 240 kg whilst the smallest (the upland moa) was the size of a sheep.

Until now scientists had thought that the huge difference in size between the species determined their foraging behaviour as well as what, when and where they ate (ie their ecological niche).

Co-author Professor Paul Scofield from Canterbury Museum says that the team took the most complete skulls of each species of moa from the collections of Canterbury Museum and Te Papa Tongarewa and scanned those using medical CT (Computed Tomography) scanners.

"We then produced highly accurate 3D models of each. This wasn't a simple job as we didn't have a single skull that was perfect so we used sophisticated digital cloning techniques to digitally reconstruct accurate osteological models for each species," Professor Scofield said.

Using the medical MRI scans of the mummified remains, Dr Johnston digitally reconstructed the muscles of each species.

"Each moa species has a characteristic bill shape and the reasons for this have not previously been defined," says Dr Johnston. "Charles Darwin had an easier time investigating a similar situation in Galapagos finches, as the differences are more extreme and the diets are obvious in that group of birds."

Software used by civil engineers after the Canterbury Earthquakes to identify weak or unsound buildings, was used to test the strength and structure of each moa species' bill.

These were compared to each other and to two living relatives, the emu and cassowary. The models simulated the response of the skull to different biting and feeding behaviours including clipping twigs and pulling, twisting or bowing head motions to remove foliage.

The skull mechanics of moa were found to be surprisingly diverse. The little bush moa had a relatively short, sharp-edged bill and was superior among moa at cutting twigs and branches, supporting the proposition that they primarily fed on fibrous material from trees and shrubs.

At the opposite extreme, the coastal moa had a relatively weak skull compared to all other species which may have forced them to travel further than other moa in search of suitable food, such as soft fruit and leaves.

Dr Trevor Worthy (a New Zealander working at Flinders University in Australia) says "until now we have been limited in assessing anatomical function to examining the external aspect of bones. This new technology allows us to bring new life to old bones and to get one step closer to understanding the birds they came from."

"Little has been known about how New Zealand's ecosystem evolved, largely because we know so little about how moa lived and co-existed," says Associate Professor Stephen Wroe, leader of the Function, Evolution and Anatomy Research (FEAR) laboratory at the University of New England (Australia).

"This new research advances our understanding about the feeding behaviours of the moa species and their impact on New Zealand's unique and distinctive flora."

Source: University of Auckland [January 14, 2016]