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A new analysis has put flesh on 22 bones believed to belong to the mysterious dodo, shedding some light on the life of the flightless bird that got extinct towards the end of the 17th century.
Based on the accounts of Dutch sailors, the bird has been immortalized in literature, art, and songs with descriptions like bulbous-beaked, puny-winged, plump, and so on. One Thomas Herbert after visiting Mauritius reported the dodo as having “eyes like diamonds, train three small plumes, downy feathers, short and disproportionable.” But few scientific facts have been revealed about the helpless bird.
Now, scientists analyzing remains of the peculiar avians have recreated the dodo’s existence by piecing together aspects of their lives – like when they began laying eggs, shed and regrew their plumage each year, and how they reached maturity fast.
Before this study, the only thing researchers knew about the existence of these birds was that they were a bigger version of the pigeon, weighing about 10 kilos, says first author and paleontologist Delphine Angst of the University of Cape Town in South Africa.
Dodos were native to the Indian Ocean island of Mauritius but got wiped out after the arrival of Dutch sailors, who are thought to have pursued them for their tasty meat. Some of the speculated factors that ended their lineage include competition for food, habitat destruction, and hunting.
Published in the journal Scientific Reports, Angst and her team from the Natural History Museum in London and Tring outline how they analyzed 22 leg and wing bones thought to have belonged to different dodos. Angst says their analyses were made easier because the bird was contemporaneous with humans as recent as 300 years ago, making several documents with sailors’ descriptions available. In typical cases, paleontologists usually have only bones to use for making theories about the life of an extinct species.
Various kinds of microscope views enabled the research team to identify an almost grown-up dodo. The results showed that its bones have three layers of tissue just like most of the modern birds. The bones were built with collagen fibers and other materials in a disorderly pattern, showing the chic grew fast. When they achieved sexual maturity, the bones started developing much slower.
And there is much more, noted Angst. The females laid down a unique type of tissue inside their bones during ovulation. The tissue supplied calcium for egg production. She says they identified several specimens with that particular type of bone, indicating for sure that the sample belonged to an ovulating female. As for the bones that did not have the extra tissue, Angst says they were unable to determine the sex.
The beautiful island of Mauritius had tendencies for harsh weather, which had a significant influence on the bird’s life cycle. Between November and March, heavy rains, cyclones, and speedy winds would destroy flowers, fruits, and leaves, causing food shortages. In response, dodos would breed in August, just after enjoying the “fat” season. Chicks rapidly grew to almost adult-size and reached sexual maturity within two to four months after they hatched, just before the cyclones began. This calendar increased their chance of surviving the island’s limited resources during the “thin” season, the team found.
The study also painted a picture of the bird’s plumage. After birds molt, they draw calcium from the inside layers of their bones to make new fathers, leaving telltale holes in the internal walls of their bones. This phenomenon is seen in several kinds of birds, including penguins and pigeons. The researchers reported that some of the specimens showed the birds died while they were molting. In March, dodos’ tail feathers and wings would get shed off, and by the end of July, all their feathers would be replaced in readiness for the breeding season.
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The molting feature could also be the reason why there were significant disparities in the contemporary descriptions of dodos. For a long time, it was believed the recounts were different because they were false. However, the researchers realized people were witnessing the birds at various stages in their molting cycle.
The sailors who reported dodos as having a downy plumage probably saw them on the onset of molting, while those who described the birds as sporting gray or having black feathers encountered them between molting periods.
By further examining tell-tale signs within the bones, the scientists were able to reveal precisely when such events occurred. During the periods when resources were scarce, the outer bone layer stopped growing, leaving regular lines which suggest arrested growth was a seasonal event: the November-to-March period.
The researchers determined the time of the year when the dodos ovulated or molted by examining the thickness of the bone deposited between those lines. They probably molted between March and July, “a suggestion that fits with the historical accounts of the bird’s plumage,” says Angst. Ovulation likely occurred early in August and chicks reached full size by November, she noted.
The research is a remarkable illustration of how scientific techniques can be used to unscramble the biology of extinct creatures, observed Daniel Field, an avian palaeobiologist from the University of Bath.