(left) Illustrations from the voyage of VOC Gelderland, 1602; (right) W.Y. Bontekoe, ca. 1646

Svelte no more. The dodos at left were drawn during a 1602 Dutch voyage; at right, a 1646 depiction shows the fatter frame that settled in the popular imagination.

How Much Did the Dodo Really Weigh?

Helen Fields is a freelance science writer based in Washington, D.C.

Dodos just got a bit slimmer—or maybe they didn't. A new paper challenges the popular conception that this pigeon, which went extinct more than 300 years ago, was comically plump, instead arguing that it weighed just a bit more than a wild turkey. But in another report, critics say the dodo wasn't quite that svelte.

Dodos weren't always thought of as fat. When Dutch ships first came across them on their way across the Indian Ocean, on the uninhabited island of Mauritius, the drawings that came back to Europe showed a slender bird, almost scrawny, with stumpy wings. But a few decades later, images of the bird had grown grotesquely blubberous.

Why the weight gain? Later artists could have been depicting dodos that were overfed in captivity. Or they could have been influenced by a 17th and 18th century trend in livestock art, which emphasized the delectable fattiness of new breeds of cattle and sheep, says Julian Hume, a paleontologist and artist who has written a book about the dodo and is a research associate at the Natural History Museum in London. "Each person wanted their animal to be bigger, fatter than the last," he says. "I think all these illustrations came from trying to make the bird look even more spectacular than it was."

But, contrary to the popular image, scientists have known for decades that the dodo wasn't as fat as its portraitists made it seem. In the early 1990s, the National Museums Scotland in Edinburgh wanted to come up with a new stuffed dodo for its display of vertebrates. The last known stuffed dodo, in Oxford, had been eaten badly by moths and discarded.

So the museum's vertebrate biologist Andrew Kitchener set about trying to figure out what a dodo would have looked like. In one set of experiments, he constructed a scale model of a dodo—based on bones in museum collections—from wire, cardboard, and plasticine muscles; the resulting bird was quite slim. In another, he weighed dodo bones to work out how much mass they could have supported, drawing on data from the leg bones of other members of the pigeon family. Kitchener eventually concluded that the dodo was a much slimmer bird than artists made it look, probably in the range of 10.5 to 17.5 kilograms.

In the new study, researchers claim that the dodo was slimmer still. A team including Delphine Angst, a graduate student in paleontology at the Natural History Museum in Paris, compiled measurements of 75 dodo leg bones—about 25 each of femur, tibiotarsus, and tarsometatarsus—from 14 museums. From these, Angst and her colleagues came up with a body mass of about 10 kilograms, as they reported last month in the journal Naturwissenschaften.

But in a study published this month in the same journal, another team challenges these findings. It criticizes the way Angst's team used the leg dimensions, suggesting that the femur is more relevant than the other bones; instead, the new team argues, a range of 9.5 to 18 kilograms is more realistic for the dodo's weight.

Getting the figures right is important, says one of the critics, Antoine Louchart, a paleo-ornithologist at the University of Lyon in France, because understanding the dodo's proper body size helps scientists understand how birds evolve on islands. "When you include these extinct species, you see that there's a trend of body size evolution of birds on islands," he says: Large birds tend to get larger, whereas small birds tend to get smaller, which is different from the usual trend for mammals.

Kitchener seems amused by the whole debate. "It's really quite funny, because I did that paper back in 1993, and all the stuff keeps being repeated by various people over time," he says. As to why people continue to be fascinated by an animal that went extinct hundreds of years ago, he credits the dodo's unique appearance. "They're such a bizarre-looking bird," he says. "I'd have loved to see a live one. ... This huge, great pigeon strutting around a lawn somewhere. And the great thing is, we could've just weighed it and not bothered with all this."

Posted in Paleontology