Dodo Bird

The Dodo (Raphus cucullatus) is an extinct flightless bird that was endemic to the island of Mauritius, east of Madagascar in the Indian Ocean. Its closest genetic relative was the also extinct Rodrigues Solitaire, the two forming the subfamily Raphinae of the family of pigeons and doves. The closest living relative of the Dodo is the Nicobar Pigeon. A white Dodo was once incorrectly thought to have existed on the nearby island ofRéunion.

Subfossil remains show the Dodo was about 1 metre (3.3 feet) tall and may have weighed 10–18 kg (22–40 lb) in the wild. The Dodo's appearance in life is evidenced only by drawings, paintings and written accounts from the 17th century. Because these vary considerably, and because only some illustrations are known to have been drawn from live specimens, its exact appearance in life remains unresolved. Similarly, little is known with certainty about its habitat and behaviour. It has been depicted with brownish-grey plumage, yellow feet, a tuft of tail feathers, a grey, naked head, and a black, yellow, and green beak. It used gizzard stones to help digest its food, which is thought to have included fruits, and its mainhabitat is believed to have been the woods in the drier coastal areas of Mauritius. One account states its clutch consisted of a single egg. It is presumed that the Dodo became flightless because of the ready availability of abundant food sources and a relative absence of predators on Mauritius.

The first recorded mention of the Dodo was by Dutch sailors in 1598. In the following years, the bird was hunted by sailors, their domesticatedanimals, and invasive species introduced during that time. The last widely accepted sighting of a Dodo was in 1662. Its extinction was not immediately noticed, and some considered it to be a mythical creature. In the 19th century, research was conducted on a small quantity of remains of four specimens that had been brought to Europe in the early 17th century. Among these is a dried head, the only soft tissue of the Dodo that remains today. Since then, a large amount of subfossil material has been collected from Mauritius, mostly from the Mare aux Songesswamp. The extinction of the Dodo within less than a century of its discovery called attention to the previously unrecognised problem of human involvement in the disappearance of entire species. The Dodo achieved widespread recognition from its role in the story of Alice in Wonderland, and it has since become a fixture in popular culture, often as a symbol of extinction and obsolescence. It is frequently used as a mascot on Mauritius.

Taxonomy

The Dodo had variously been declared a small ostrich, a rail, an albatross, or a vulture, by 19th century scientists. In 1842, Johannes Theodor Reinhardt proposed that Dodos were ground pigeons, based on studies of a Dodo skull he had discovered in the royal Danish collection at Copenhagen. This view was met with ridicule, but was later supported by Hugh Edwin Strickland and Alexander Gordon Melville in their 1848 monograph The Dodo and Its Kindred, which attempted to separate myth from reality. After dissecting the preserved head and foot of the specimen at the Oxford University Museum and comparing it with the few remains then available of the extinct Rodrigues Solitaire (Pezophaps solitaria) they concluded that the two were closely related. Strickland stated that although not identical, these birds shared many distinguishing features of the leg bones, otherwise known only in pigeons.

The Dodo was anatomically similar to pigeons in many features. Strickland pointed to the very short keratinous portion of the beak, with its long, slender, naked basal part. Other pigeons also have bare skin around their eyes, almost reaching their beak, as in Dodos. The forehead was high in relation to the beak, and thenostril was located low on the middle of the beak and surrounded by skin, a combination of features shared only with pigeons. The legs of the Dodo were generally more similar to those of terrestrial pigeons than of other birds, both in their scales and in their skeletal features. Depictions of the large crop hinted at a relationship with pigeons, in which this feature is more developed than in other birds. Pigeons generally have very small clutches, and the Dodo is said to have laid a single egg. Like pigeons, the Dodo lacked the vomer and septum of the nostrils, and it shared details in the mandible, the zygomatic bone, the palate and the hallux. The Dodo differed from other pigeons mainly in the small size of the wings and the large size of the beak in proportion to the rest of the cranium.

Sketch of the Oxford specimen head before its dissection

Throughout the 19th century, several species were classified as congeneric with the Dodo, including the Rodrigues Solitaire and the Réunion Solitaire, as Didus solitarius and Raphus solitarius, respectively (Didus and Raphus being names for the Dodo genus used by different authors of the time). An atypical 17th-century description of a Dodo and bones found on Rodrigues, now known to have belonged to the Rodrigues Solitaire, led Abraham Dee Bartlett to name a new species, Didus nazarenus, in 1852. Based on Solitaire remains, it is now a synonym of that species. Crude drawings of theRed Rail of Mauritius were also misinterpreted as Dodo species, Didus broeckii and Didus herberti.

Evolution

For many years the Dodo and the Rodrigues Solitaire were placed in a family of their own, the Raphidae (formerly Dididae), because their exact relationships with other pigeons were unresolved. Each was placed in its own monotypic family (Raphidae and Pezophapidae, respectively), as it was thought that they had evolved their similar features independently. Osteological and molecular data has since led to the dissolution of the family Raphidae, and the Dodo and Solitaire are now placed in their own subfamily, Raphinae, in the family Columbidae.

Comparison of mitochondrial cytochrome b and 12S rRNA sequences isolated from a Dodo tarsal and a Rodrigues Solitaire femur confirmed their close relationship and their placement within theColumbidae. The genetic evidence was interpreted as showing the Southeast Asian Nicobar Pigeon to be their closest living relative, followed by the crowned pigeons of New Guinea and the superficially Dodo-like Tooth-billed Pigeon from Samoa. The generic name of the latter is Didunculus ("little Dodo"), and it was called "Dodlet" by Richard Owen. The following cladogram, from Shapiro and colleagues (2002), shows the Dodo's closest relationships within the Columbidae, a clade consisting of generally ground-dwelling island endemics.

Foot of the Oxford specimen, used as source for the genetic study

	Goura victoria (Victoria Crowned Pigeon) Caloenas nicobarica (Nicobar Pigeon) Pezophaps solitaria (Rodrigues Solitaire) Raphus cucullatus (Dodo) Didunculus strigirostris (Tooth-billed Pigeon)

A similar cladogram was published in 2007, inverting the placement of Goura and Dicunculus and including the Pheasant Pigeon and the Thick-billed Ground Pigeon at the base of the clade. The 2002 study indicated that the ancestors of the Solitaire and the Dodo diverged around the Paleogene-Neogeneboundary. The Mascarene Islands (Mauritius, Réunion, and Rodrigues), are of volcanic origin and are less than 10 million years old. Therefore, the ancestors of both birds probably remained capable of flight for a considerable time after the separation of their lineage. The lack of mammalian herbivores competing for resources on these islands allowed the Solitaire and the Dodo to attain very large sizes. The DNA obtained from the Oxford specimen is degraded, and no usable DNA has been extracted from subfossil remains, so these findings still need to be independently verified. The Dodo lost the ability to fly owing to the lack of mammalian predators on Mauritius. Another large, flightless pigeon, the Viti Levu Giant Pigeon (Natunaornis gigoura), was described in 2001 from subfossil material from Fiji. It was only slightly smaller than the Dodo and the Solitaire, and it too is thought to have been related to the crowned pigeons.

Description

As no complete Dodo specimens exist, its external appearance, such as plumage and colouration, is hard to determine. Illustrations and written accounts of encounters with the Dodo between its discovery and its extinction (1598–1662) are the primary evidence for its external appearance.According to most representations, the Dodo had greyish or brownish plumage, with lighter primary feathers and a tuft of curly light feathers high on its rear end. The head was grey and naked, the beak green, black and yellow, and the legs were stout and yellowish, with black claws. Subfossil remains and remnants of the birds that were brought to Europe in the 17th century show that they were very large birds, 1 metre (3.3 feet) tall, and possibly weighing up to 23 kilograms (51 lb). The higher weights have been attributed to birds in captivity; weights in the wild were estimated to have been in the range 10.6–21.1 kg (23–47 lb). A later estimate gives an average weight as low as 10.2 kg (22 lb). This has been questioned, and there is still some controversy. It has been suggested that the weight depended on the season, and that individuals were fat during cool seasons, but less so during hot. The bird was sexually dimorphic: males were larger and had proportionally longer beaks. The beak was up to 23 centimetres (9.1 in) in length and had a hooked point. A study of the few remaining feathers on the Oxford specimen head showed that they were pennaceous rather than plumaceous (downy) and most similar to those of other pigeons.

Many of the skeletal features that distinguish the Dodo and the Rodrigues Solitaire, its closest relative, from pigeons have been attributed to their flightlessness. The pelvic elements were thicker than those of flighted pigeons to support the higher weight, and the pectoral region and the small wings were paedomorphic, meaning that they were underdeveloped and retained juvenile features. The skull, trunk and pelvic limbs were peramorphic, meaning that they changed considerably with age. The Dodo shared several other traits with the Rodrigues Solitaire, such as features of the skull, pelvis, and sternum, as well as their large size. It differed in other aspects, such as being more robust and shorter than the Solitaire, having a larger skull and beak, a rounded skull roof, and smaller orbits. The Dodo's neck and legs were proportionally shorter, and it did not possess an equivalent to the knob present on the Solitaire's wrists.

Extinction

Like many animals that evolved in isolation from significant predators, the Dodo was entirelyfearless of humans. This fearlessness and its inability to fly made the Dodo easy prey for sailors. Although some scattered reports describe mass killings of Dodos for ships' provisions, archaeological investigations have found scant evidence of human predation. Bones of at least two Dodos were found in caves at Baie du Cap that sheltered fugitive slavesand convicts in the 17th century and would not have been easily accessible to Dodos because of the high, broken terrain. The human population on Mauritius (an area of 1,860 km² or 720 sq mi) never exceeded 50 people in the 17th century, but they introduced other animals, including dogs, pigs, cats, rats, and crab-eating macaques, which plundered Dodo nests and competed for the limited food resources. At the same time, humans destroyed the Dodo's forest habitat. The impact of these introduced animals, especially the pigs and macaques, on the Dodo population is currently considered more severe than that of hunting. Rats were perhaps not much of a threat to the nests, since Dodos would have been used to dealing with local land crabs.

It has been suggested that the Dodo may already have been rare or localised before the arrival of humans on Mauritius, since it would have been unlikely to become extinct so rapidly if it had occupied all the remote areas of the island. A 2005 expedition found subfossil remains of Dodos and other animals killed by a flash flood. Such mass mortalities would have further jeopardised a species already in danger of becoming extinct.

Frederick William Frohawk's restoration from Rothschild's 1907 book Extinct Birds

Some controversy surrounds the date of their extinction. The last widely accepted record of a Dodo sighting is the 1662 report by shipwrecked mariner Volkert Evertsz of the Dutch shipArnhem, who described birds caught on a small islet off Mauritius, now suggested to beAmber Island:

These animals on our coming up to them stared at us and remained quiet where they stand, not knowing whether they had wings to fly away or legs to run off, and suffering us to approach them as close as we pleased. Amongst these birds were those which in India they call Dod-aersen (being a kind of very big goose); these birds are unable to fly, and instead of wings, they merely have a few small pins, yet they can run very swiftly. We drove them together into one place in such a manner that we could catch them with our hands, and when we held one of them by its leg, and that upon this it made a great noise, the others all on a sudden came running as fast as they could to its assistance, and by which they were caught and made prisoners also.

Pieter van den Broecke's 1617 drawing of a Dodo, a one-horned sheep, and a Red Rail

The Dodos on this islet may not necessarily have been the last members of the species.The last claimed sighting of a Dodo was reported in the hunting records of Isaac Johannes Lamotius in 1688. Statistical analysis of these records by Roberts and Solow gives a new estimated extinction date of 1693, with a 95% confidence interval of 1688–1715. The authors also pointed out that because the last sighting before 1662 was in 1638, the Dodo was probably already quite rare by the 1660s, and thus a disputed report from 1674 by an escaped slave cannot be dismissed out of hand.

Anthony Cheke pointed out that some descriptions after 1662 use the names "Dodo" and "Dodaers" when referring to the Red Rail, indicating that they had been transferred to it after the disappearance of the Dodo itself. Cheke therefore points to the 1662 description as the last credible observation. A 1668 account by English traveller John Marshall, who used the names "Dodo" and "Red Hen" interchangeably for the Red Rail, mentioned that the meat was "hard", which echoes the description of the meat in the 1681 account. Even the 1662 account has been questioned by Errol Fuller, as the reaction to distress cries matches what was described for the Red Rail. Until this explanation was proposed, a description of "Dodos" from 1681 was thought to be the last account, and that date still has proponents. It is unlikely the issue will ever be resolved, unless late reports mentioning the name alongside a physical description are rediscovered. The IUCN Red List accepts Cheke's rationale for choosing the 1662 date, taking all subsequent reports to refer to Red Rails. In any case, the Dodo was probably extinct by 1700, about a century after its discovery in 1598. The Dutch left Mauritius in 1710, but by then the Dodo and most of the large terrestrial vertebrates there had become extinct.

Even though the rareness of the Dodo was reported already in the 17th century, its extinction was not recognised until the 19th century. This was partly because, for religious reasons, extinction was not believed possible until later proved so by Georges Cuvier, and partly because many scientists doubted that the Dodo had ever existed. It seemed altogether too strange a creature, and many believed it a myth. The bird was first used as an example of human-induced extinction in Penny Magazine in 1833.

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