Reconstruction of the dodo. Picture: JULIAN HUME
Reconstruction of the dodo. Picture: JULIAN HUME

Hundreds of years after the dodo became extinct, the micro-structure of its bones has given scientists new clues about how it lived.

The dodo was endemic to Mauritius, and was first described by Dutch sailors in 1598. Less than 100 years later, the large, flightless bird had become extinct, thanks to hunting and the introduction of invasive species such as monkeys and rats.

It met its demise long before scientists could make detailed scientific records: the little that was known about it came from sailors’ reports, which were imprecise and contradictory. Now an international team of researchers, that includes scientists from the University of Cape Town (UCT), has used its bones to piece together the puzzle of its breeding and moulting cycle.

"The dodo has been reasonably well-studied, but the sad thing is there is so little known about its natural history — how it grew and reproduced. Our study was able to fill in many of these gaps," said UCT paleobiologist Anusuya Chinsamy-Turan, co-author of a study describing the research which was published in Nature Scientific Reports last month.

The scientists scrutinised the micro-structure of 22 bones from 22 dodos from different fossil sites on Mauritius. Like most modern birds, the dodo’s bones had three layers of tissue, the outermost one of which is only found in adults. This outer layer of bone stops growing when resources such as food are scarce, leaving a line, rather like a growth ring in a tree. The bones have regular lines, which the scientists said suggested the dodo’s growth halted during the summer months, when cyclones and other rough weather made food scarce.

"We were also able to show that, unlike modern pigeons, its closest relative, the dodo took several years to reach full size," said Chinsamy-Turan. "We also found some of the specimens had medullary bones (laid down when birds ovulate, indicating they were female), and we could see the effect of moulting, which leaves cavities in the bone wall."

The research suggests that rather than being inaccurate, the varying historical accounts of the dodo’s appearance may simply be descriptions of the bird at different stages of its moulting cycle: sailors who described them as having downy feathers probably saw them just after moulting began, while those who described dodos with black or grey feathers saw them between moulting periods.

The authors proposed that the breeding season for dodos started around August, when females ovulated. Once the chicks hatched, they grew rapidly so they could cope with the tough conditions of the southern hemisphere summer months, then began moulting around March, with the feathers in the wings and the tail replaced first. By the end of July the moult would have been completed, ready for the next breeding season.

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