Dutch sailors gave the first accounts of the dodo in 1598 when they first landed on Mauritius describing a large, flightless bird. The birds’ inability to fly no doubt increased its vulnerability and the sailors hunted the birds for their meat. That and the introduction of invasive species drove the birds to extinction in 1693.
While the remains, mainly bones, have been extensively studied, the ecology of dodo – its relation with its environment – has been hard to picture. Much has remained a mystery. Doves and pigeons are the bird’s closest surviving relatives and extrapolating up from these to a long-extinct bird weighing around 10 kilos is hard to do.
So, for the first time, researchers have combined intensive microscope analysis of the birds’ bones with contemporaneous accounts written by the sailors. Delphine Angst, a post doc at the Palaeobiology Research Group at the University of Cape Town in South Africa led the study, published in the journal, Scientific Reports. The team have revealed aspects of the dodo’s life: from when they laid eggs to how quickly they reached adulthood, and even that they shed and regrew their plumage each year.
:Before our study the only things we knew about the ecology of these birds was that they were a big pigeon [with a body mass of] about 10 kilos,” said Delphine Angst.
Angst, along with colleagues from the Natural History Museum in London and Tring, describe how they examined thin cross-sections of 22 leg and wing bones under a microscope, thought to be from 22 different dodos. The results, described in an article appearing in the UK’s Guardian newspaper, show that, like the majority of birds we see around us, the adult dodo had three layers of bone tissue. Juveniles had only two, ‘For the first time we can say that for sure these specimens from a juvenile, even if it looks like it is almost an adult in terms of size.’ It seems the young grew very rapidly.
The study also reveals that the females produced a type of tissue in their bones when ovulating, which provided a supply of calcium for egg production. Quoted in the Guardian, Angst explained, “In our samples we found several specimens with this specific kind of central bone and then we [can tell] for sure that this specimen is a female and it is a female during ovulation, which is quite cool.” She added that for the other bones, without the extra tissue, it was unclear to which sex they belonged.
For a long time the differences in contemporary descriptions were believed to be due to inaccurate reporting but the new analysis throws light on the discrepancies. The sailors appear to be describing the birds in different stages of moult. The authors propose that mariners who described the birds as having a downy plumage probably saw them just after moulting began, with those describing dodos as sporting grey or black feathers seeing them between periods of moulting.
The bones gave up more secrets, allowing the team to identify when the moulting was likely to have occurred. When resources are scarce the outer layer of bone stops growing, leaving a line. Researchers noted the lines appear regularly suggesting the arrested growth was likely to be seasonal. The paper’s authors say this could reflect the summer months, November to March, when cyclones and other poor weather is frequent in Mauritius.
Quoted by the BBC, Angst said, “It’s difficult to know what was the real impact of humans if we don’t know the ecology of this bird and the ecology of the Mauritius island at this time. So that’s one step to understand the ecology of these birds and the global ecosystem of Mauritius and to say, ‘Okay, when the human arrived what exactly did they do wrong and why did these birds became extinct so quickly’.”
Cordis source: Based on media reports