Driven to extinction: Who killed the Dodo?

For such an iconic animal, it seems strange that we know next to nothing about the dodo - except, of course, that it is dead. We don't know how it lived, what it ate, how many eggs it sat on or even whether it was fat or thin.

But that could all change with a scientific expedition just begun in Mauritius, the remote island in the Indian Ocean where the dodo lived for millions of years before being driven to extinction in the late 17th century, just 80 years after it was sighted by European sailors.

British and Dutch scientists have joined forces to excavate a unique dodo burial ground where the bones of hundreds and possibly thousands of birds have been preserved in marshland for more than 10,000 years. It will be the first time scientists have had access to well-preserved dodo remains that have remained untouched. At last, some light maybe shed on a mysterious and emblematic creature that has come to epitomise how easy it is for man to wipe out a species.

The Mare aux Songes area of Mauritius was once a dry coastal forest which later became marshland. Last year scientists said they thought the site contained a mass of bones from a rich variety of animals - giant tortoises, dodos and other extinct birds and reptiles - all of which long pre-date the arrival of the first humans to inhabit Mauritius in 1598. "The discovery is of huge importance and will give us a new understanding of how dodos lived," explained Julian Hume, a postdoctoral research fellow at the Natural History Museum in London who has helped to organise the expedition.

"For the first time we will be able to answer questions like how many dodos lived on the island and what did they eat? Young dodo remains may also reveal how they bred and what kind of parents they might have been," Dr Hume said.

"We still don't even know what it ate and why it had that unusually large, hooked bill. It may have been for sexual display or was it to dig out roots for eating? These are some of the questions we want to answer."

The first written description of a dodo comes from a Dutch sailor called Heyndrick Dircksz Jolinck, who led an expedition to the island in 1598. He described large birds with wings no bigger than a pigeon's - the wings were so small they rendered the birds flightless. Jolinck also gave a strong hint about why the dodos became so sought after by sailors. "These particular birds have a stomach so large it could provide two men with a tasty meal and was actually the most delicious part of the bird," he wrote.

Although hunting and indiscriminate killing was to take their toll, it was the invasion of the island by alien species such as rats, pigs and other domestic animals that saw the dodo condemned to extinction. The chicks and eggs of the ground-laying bird became easy fodder. Habitat destruction also played its part and by 1680, just eight decades after the island was claimed as Dutch territory, the last dodo had died. All that remained were a few moth-eaten specimens in European museums. The most famous was the Oxford dodo, which became so badly decomposed that much of it had to be burnt. Only the head and one leg remains today at the University Museum.

It was this specimen that was probably the inspiration for Lewis Carroll's "Dodo" in Alice's Adventures in Wonderland.

Intriguingly, according to Dr Hume's research, is it also possible the Oxford dodo was the only living specimen to have arrived in Europe. This bird was described by Sir Hamon L'Estrange in London in 1638. He saw a picture of an unfamiliar "fowle" hanging upon a cloth outside a shop - clearly an advertisement to see a strange bird - which led Sir Hamon to investigate. His subsequent description is the only documented account of a living dodo in Britain. "It was kept in a chamber, and was a great fowle somewhat bigger than the largest Turkey Cock, and so legged and footed, but stouter and thicker and of a more erect shape, coloured before like the breast of a young cock fesan, and on the back a dunn or deare colour. The keeper called it a Dodo, and in the ende of a chymney in the chamber there lay a heape of large pebble stones, wherof hee gave it many in our sight, some as big as nutmegs, and the keeper told us she eats them (conducing to digestion)."

Much of what is known about the appearance of the dodo comes from contemporary drawings and paintings. But these were often inaccurate, subject to the vagaries and fashions of the time - such as the 17th century predilection for painting over-plump birds.

"The dodo, one of the most documented and famous of birds and a leading contender as the icon of extinction, has endured more than its fair share of overzealous misinterpretation," said Dr Hume, who is himself a skilled artist. After the last dodo was seen alive, it quickly became an almost mythical creature for sailors and travellers. In fact it became so mythologised that some eminent 19th-century scholars began to doubt that it ever existed, believing that the rather poorly preserved specimens were elaborate hoaxes.

In fact all of these specimens were made from the incomplete skeletons of many different individuals. Trying to guess what the real dodo looked like was an uphill struggle.

One problem was its weight. Many of the early paintings depict it as an overweight, almost obese creature that could barely support itself. But, at least one illustration dating from the first Dutch exploration of 1598 depicts the dodo as a rather slim, even nimble bird. In reality, it is possible that the dodo was both fat and slim. In other words it may have been adapted to putting on weight quickly in times of plenty - during the wet season for instance when there was lots of ripe fruit to eat - which would have allowed it to survive the leaner times of the dry season.

Dodos kept in captivity could just have been overfed, which is why they tended to look far fatter than other birds of similar shape and size.

Lingering 19th-century doubts about the existence of the dodo were finally dispelled in 1865 with the discovery of the bones of about 300 dodos that had died out long before the arrival of the first Europeans to Mauritius.

Unfortunately this excavation was not undertaken in a very scientific manner and many of the specimens were mishandled, leading to further confusion about the dodo's true anatomy.

The site where these bones were found was subsequently filled in by the British military in the 1940s using builders' rubble. It was recently earmarked for further development when Dr Hume and his colleagues decided to seek permission to dig below the builders' hardcore.

Last December they announced they had struck palaeontological gold with the discovery of a new, untouched layer of thousands of bones dating back at least 10,000 years.

"This is new material and it is absolutely free of human contamination. We're going to collect material that has not been touched in any shape or form," Dr Hume said.

One hope is that the scientists will find the first complete articulated skeleton of an individual dodo, which will help them to figure out how it moved around, whether it walked with a waddle or hopped with a skip.

The bones are so well preserved that the researchers also hope to extract DNA that will give further insights into the bird's origins. Professor Alan Cooper, former director of the Ancient Biomolecules Centre at Oxford, has already been able to extract limited quantities of DNA from the Oxford dodo - the only specimen with soft tissue. This study revealed the dodo was related to the solitaire, another extinct bird that lived on nearby Rodrigues Island, which is part of the same Mascarene island chain.

"The data suggests that the dodo and solitaire speciated [separated] from each other around 26 million years ago, about the same time that geologists think the first, now submerged, Mascarene islands emerged," Professor Cooper said.

" Mauritius and Rodrigues islands are much younger - eight and 1.5 million years respectively - implying the dodo and solitaire used the now sunken island chain as stepping stones."

Most intriguingly, the DNA study showed that the dodo was in effect a giant pigeon. Its nearest living relative is the Nicobar pigeon from south-east Asia. The next nearest relatives are the crowned pigeons of New Guinea and the tooth-billed pigeons of Samoa.

The unusual looks of the dodo - epitomised by the oversized, hooked beak - were the result of the unusual forces of natural selection that often occur on remote islands. When large animals get stranded on islands they tend to become dwarfs, while smaller animals such as birds tend to get bigger in order to build up bulk for times of near starvation. This is precisely what happened to the dodo. It quickly lost its flight muscles - which are expensive to maintain in terms of energy - because there were no predators on the island from which to escape.

That all changed in 1598 when the first European settlers decided to set up home in dodo land. The rest - like the dodo - is history.