The dodo (Raphus cucullatus) is an extinctflightless bird that was endemic to the island of Mauritius, which is east of Madagascar in the Indian Ocean. The dodo's closest relative was the also-extinct and flightless Rodrigues solitaire. The two formed the subfamilyRaphinae, a clade of extinct flightless birds that were a part of the family which includes pigeons and doves. The closest living relative of the dodo is the Nicobar pigeon. A white dodo was once thought to have existed on the nearby island of Réunion, but it is now believed that this assumption was merely confusion based on the also-extinct Réunion ibis and paintings of white dodos.
Subfossil remains show the dodo measured around 62.6–75 centimetres (2.05–2.46 ft) in height and may have weighed 10.6–17.5 kg (23–39 lb) in the wild. The dodo's appearance in life is evidenced only by drawings, paintings, and written accounts from the 17th century. Since these portraits vary considerably, and since only some of the illustrations are known to have been drawn from live specimens, the dodos' exact appearance in life remains unresolved, and little is known about its 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 main habitat 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. Though the dodo has historically been portrayed as being fat and clumsy, it is now thought to have been well-adapted for its ecosystem.
The first recorded mention of the dodo was by Dutch sailors in 1598. In the following years, the bird was hunted by sailors and invasive species, while its habitat was being destroyed. The last widely accepted sighting of a dodo was in 1662. Its extinction was not immediately noticed, and some considered the bird to be a myth. 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 on Mauritius, mostly from the Mare aux Songes swamp. 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's Adventures in Wonderland, and it has since become a fixture in popular culture, often as a symbol of extinction and obsolescence.
Taxonomy
Skull in the Zoological Museum of Copenhagen (above), and right half of the Oxford specimen's head (below); examination of these led to the dodo being classified as a pigeon in the 1840s
The dodo was variously declared a small ostrich, a rail, an albatross, or a vulture, by early scientists.[3] In 1842, Danish zoologist Johannes Theodor Reinhardt proposed that dodos were ground pigeons, based on studies of a dodo skull he had discovered in the collection of the Natural History Museum of Denmark. This view was met with ridicule, but was later supported by English naturalists Hugh Edwin Strickland and Alexander Gordon Melville in their 1848 monographThe Dodo and Its Kindred, which attempted to separate myth from reality.[4][5] 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.[6]
Strickland and Melville established that the dodo was anatomically similar to pigeons in many features. They 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 the nostril 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.[6]
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.[7] Based on solitaire remains, it is now a synonym of that species.[8] Crude drawings of the red railofMauritius were also misinterpreted as dodo species; Didus broeckii and Didus herberti.[9]
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 also placed in its own monotypic family (Raphidae and Pezophapidae, respectively), as it was thought that they had evolved their similarities independently.[10]Osteological and DNA analysis has since led to the dissolution of the family Raphidae, and the dodo and solitaire are now placed in their own subfamily, Raphinae, within the family Columbidae.[11]
Evolution
The Nicobar pigeon is the closest living relative of the dodo
In 2002, American geneticist Beth Shapiro and colleagues analysed the DNA of the dodo for the first time. Comparison of mitochondrialcytochrome b and 12S rRNAsequences isolated from a tarsal of the Oxford specimen and a femur of a Rodrigues solitaire confirmed their close relationship and their placement within the Columbidae. The genetic evidence was interpreted as showing the Southeast Asian Nicobar pigeon (Caloenas nicobarica) to be their closest living relative, followed by the crowned pigeons (Goura) of New Guinea, and the superficially dodo-like tooth-billed pigeon (Didunculus strigirostris) from Samoa (its scientific name refers to its dodo-like beak). This clade consists of generally ground-dwelling island endemic pigeons. The following cladogram shows the dodo's closest relationships within the Columbidae, based on Shapiro and colleagues, 2002:[12][13]
A similar cladogram was published in 2007, inverting the placement of Goura and Didunculus and including the pheasant pigeon (Otidiphaps nobilis) and the thick-billed ground pigeon (Trugon terrestris) at the base of the clade.[14] The DNA used in these studies was obtained from the Oxford specimen, and since this material is degraded, and no usable DNA has been extracted from subfossil remains, these findings still need to be independently verified.[15] Based on behavioural and morphological evidence, Jolyon C. Parish proposed that the dodo and Rodrigues solitaire should be placed in the subfamily Gourinae along with the Goura pigeons and others, in agreement with the genetic evidence.[16] In 2014, DNA of the only known specimen of the recently extinct spotted green pigeon (Caloenas maculata) was analysed, and it was found to be a close relative of the Nicobar pigeon, and thus also the dodo and Rodrigues solitaire.[17]
The 2002 study indicated that the ancestors of the dodo and the solitaire diverged around the Paleogene-Neogene boundary, about 23.03 million years ago. 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.[18] The Nicobar and spotted green pigeon were placed at the base of a lineage leading to the Raphinae, which indicates the flightless raphines had ancestors that were able to fly, were semi-terrestrial, and inhabited islands. This in turn supports the hypothesis that the ancestors of those birds reached the Mascarene islands by island hopping from South Asia.[17] The lack of mammalianherbivores competing for resources on these islands allowed the solitaire and the dodo to attain very large sizes and flightlessness.[19][20] Despite its divergent skull morphology and adaptations for larger size, many features of its skeleton remained similar to those of smaller, flying pigeons.[21] 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.[22]
Etymology
1601 engraving showing Dutch activities on the shore of Mauritius and the first published depiction of a dodo on the left (2, called "Walchvoghel")
One of the original names for the dodo was the Dutch "Walghvoghel", first used in the journal of Dutch Vice Admiral Wybrand van Warwijck, who visited Mauritius during the Second Dutch Expedition to Indonesia in 1598.[23]Walghe means "tasteless", "insipid", or "sickly", and voghel means "bird". The name was translated by Jakob Friedlib into German as WalchstökorWalchvögel. The original Dutch report titled Waarachtige Beschryving was lost, but the English translation survived:[24][16]
On their left hand was a little island which they named Heemskirk Island, and the bay it selve they called Warwick Bay... Here they taried 12. daies to refresh themselues, finding in this place great quantity of foules twice as bigge as swans, which they call Walghstocks or Wallowbirdes being very good meat. But finding an abundance of pigeons & popinnayes [parrots], they disdained any more to eat those great foules calling them Wallowbirds, that is to say lothsome or fulsome birdes.[25][26]
Another account from that voyage, perhaps the first to mention the dodo, states that the Portuguese referred to them as penguins. The meaning may not have been derived from penguin (the Portuguese referred to those birds as "fotilicaios" at the time), but from pinion, a reference to the small wings.[23] The crew of the Dutch ship Gelderland referred to the bird as "Dronte" (meaning "swollen") in 1602, a name that is still used in some languages.[27] This crew also called them "griff-eendt" and "kermisgans", in reference to fowl fattened for the Kermesse festivalinAmsterdam, which was held the day after they anchored on Mauritius.[28]
The etymology of the word dodo is unclear. Some ascribe it to the Dutch word dodoor for "sluggard", but it is more probably related to Dodaars, which means either "fat-arse" or "knot-arse", referring to the knot of feathers on the hind end.[29] The first record of the word Dodaars is in Captain Willem Van West-Zanen's journal in 1602.[30] The English writer Sir Thomas Herbert was the first to use the word dodo in print in his 1634 travelogue claiming it was referred to as such by the Portuguese, who had visited Mauritius in 1507.[28] Another Englishman, Emmanuel Altham, had used the word in a 1628 letter in which he also claimed its origin was Portuguese. The name "dodar" was introduced into English at the same time as dodo, but was only used until the 18th century.[31] As far as is known, the Portuguese never mentioned the bird. Nevertheless, some sources still state that the word dodo derives from the Portuguese word doudo (currently doido), meaning "fool" or "crazy". It has also been suggested that dodo was an onomatopoeic approximation of the bird's call, a two-note pigeon-like sound resembling "doo-doo".[32]
The Latin name cucullatus ("hooded") was first used by Juan Eusebio Nieremberg in 1635 as Cygnus cucullatus, in reference to Carolus Clusius's 1605 depiction of a dodo. In his 18th-century classic work Systema Naturae, Carl Linnaeus used cucullatus as the specific name, but combined it with the genus name Struthio (ostrich).[6]Mathurin Jacques Brisson coined the genus name Raphus (referring to the bustards) in 1760, resulting in the current name Raphus cucullatus. In 1766, Linnaeus coined the new binomial Didus ineptus (meaning "inept dodo"). This has become a synonym of the earlier name because of nomenclatural priority.[33]
Description
Size compared to a human
As no complete dodo specimens exist, its external appearance, such as plumage and colouration, is hard to determine.[23] 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.[34] 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.[35] 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.[36]
Subfossil remains and remnants of the birds that were brought to Europe in the 17th century show that dodos were very large birds, measuring around 62.6–75 cm (2.05–2.46 ft) in height.[37][38] The bird was sexually dimorphic; males were larger and had proportionally longer beaks. Weight estimates have varied from study to study. In 1993, Bradley C. Livezey proposed that males would have weighed 21 kilograms (46 lb) and females 17 kilograms (37 lb).[39] Also in 1993, Andrew C. Kitchener attributed a high contemporary weight estimate and the roundness of dodos depicted in Europe to these birds having been overfed in captivity; weights in the wild were estimated to have been in the range of 10.6–17.5 kg (23–39 lb), and fattened birds could have weighed 21.7–27.8 kg (48–61 lb).[40] A 2011 estimate by Angst and colleagues gave an average weight as low as 10.2 kg (22 lb).[41] This has also been questioned, and there is still controversy over weight estimates.[42][43] A 2016 study estimated the weight at 10.6 to 14.3 kg (23 to 32 lb), based on CT scans of composite skeletons.[44] It has also been suggested that the weight depended on the season, and that individuals were fat during cool seasons, but less so during hot.[38]
Skeleton
1848 lithographs of the Oxford dodo's skull in multiple views
The skull of the dodo differed much from those of other pigeons, especially in being more robust, the bill having a hooked tip, and in having a short cranium compared to the jaws. The upper bill was nearly twice as long as the cranium, which was short compared to those of its closest pigeon relatives. The openings of the bony nostrils were elongated along the length of the beak, and they contained no bony septum. The cranium (excluding the beak) was wider than it was long, and the frontal bone formed a dome-shape, with the highest point above the hind part of the eye sockets. The skull sloped downwards at the back. The eye sockets occupied much of the hind part of the skull. The sclerotic rings inside the eye were formed by eleven ossicles (small bones), similar to the amount in other pigeons. The mandible was slightly curved, and each half had a single fenestra (opening), as in other pigeons.[21]
Skeleton of the dodo (left) and its closest relative, the Rodrigues solitaire, not to scale
The dodo had about nineteen presynsacral vertebrae (those of the neck and thorax, including three fused into a notarium), sixteen synsacral vertebrae (those of the lumbar region and sacrum), six free tail (caudal) vertebrae, and a pygostyle. The neck had well-developed areas for muscle and ligament attachment, probably to support the heavy skull and beak. On each side, it had six ribs, four of which articulated with the sternum through sternal ribs. The sternum was large, but small in relation to the body compared to those of much smaller pigeons that are able to fly. The sternum was highly pneumatic, broad, and relatively thick in cross-section. The bones of the pectoral girdle, shoulder blades, and wing bones were reduced in size compared to those of flighted pigeon, and were more gracile compared to those of the Rodrigues solitaire, but none of the individual skeletal components had disappeared. The carpometacarpus of the dodo was more robust than that of the solitaire, however. The pelvis was wider than that of the solitaire and other relatives, yet was comparable to the proportions in some smaller, flighted pigeons. Most of the leg bones were more robust than those of extant pigeons and the solitaire, but the length proportions were little different.[21]
Many of the skeletal features that distinguish the dodo and the Rodrigues solitaire, its closest relative, from other 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.[39]
Contemporary descriptions
Dodo among birds in a Mughal Indian menagerie (left), by Ustad Mansur, c. 1625; perhaps the most accurate depiction of a live dodo, and dodo head (right) by Cornelis Saftleven from 1638, probably the last original depiction of the species
Most contemporary descriptions of the dodo are found in ship's logs and journals of the Dutch East India Company vessels that docked in Mauritius when the Dutch Empire ruled the island. These records were used as guides for future voyages.[15] Few contemporary accounts are reliable, as many seem to be based on earlier accounts, and none were written by scientists.[23] One of the earliest accounts, from van Warwijck's 1598 journal, describes the bird as follows:
Blue parrots are very numerous there, as well as other birds; among which are a kind, conspicuous for their size, larger than our swans, with huge heads only half covered with skin as if clothed with a hood. These birds lack wings, in the place of which 3 or 4 blackish feathers protrude. The tail consists of a few soft incurved feathers, which are ash coloured. These we used to call 'Walghvogel', for the reason that the longer and oftener they were cooked, the less soft and more insipid eating they became. Nevertheless their belly and breast were of a pleasant flavour and easily masticated.[45]
One of the most detailed descriptions is by Herbert in A Relation of Some Yeares Travaille into Afrique and the Greater Asia from 1634:
First here only and in Dygarrois [Rodrigues] is generated the Dodo, which for shape and rareness may antagonize the Phoenix of Arabia: her body is round and fat, few weigh less than fifty pound. It is reputed more for wonder than for food, greasie stomackes may seeke after them, but to the delicate they are offensive and of no nourishment. Her visage darts forth melancholy, as sensible of Nature's injurie in framing so great a body to be guided with complementall wings, so small and impotent, that they serve only to prove her bird. The halfe of her head is naked seeming couered with a fine vaile, her bill is crooked downwards, in midst is the thrill [nostril], from which part to the end tis a light green, mixed with pale yellow tincture; her eyes are small and like to Diamonds, round and rowling; her clothing downy feathers, her train three small plumes, short and inproportionable, her legs suiting her body, her pounces sharpe, her appetite strong and greedy. Stones and iron are digested, which description will better be conceived in her representation.[46]
Contemporary depictions
Compilation of the Gelderland ship's journal sketches from 1601 of live and recently killed dodos, attributed to Joris Laerle
The travel journal of the Dutch ship Gelderland (1601–1603), rediscovered in the 1860s, contains the only known sketches of living or recently killed specimens drawn on Mauritius. They have been attributed to the professional artist Joris Joostensz Laerle, who also drew other now-extinct Mauritian birds, and to a second, less refined artist.[47] Apart from these sketches, it is unknown how many of the twenty or so 17th-century illustrations of the dodos were drawn from life or from stuffed specimens, which affects their reliability.[23] Since dodos are otherwise only known from limited physical remains and descriptions, contemporary artworks are important to reconstruct their appearance in life. While there has been an effort since the mid-19th century to list all historical illustrations of dodos, previously unknown depictions continue to be discovered occasionally.[48]
The traditional image of the dodo is of a very fat and clumsy bird, but this view may be exaggerated. The general opinion of scientists today is that many old European depictions were based on overfed captive birds or crudely stuffed specimens.[49] It has also been suggested that the images might show dodos with puffed feathers, as part of display behaviour.[41] The Dutch painter Roelant Savery was the most prolific and influential illustrator of the dodo, having made at least twelve depictions, often showing it in the lower corners. A famous painting of his from 1626, now called Edwards's Dodo as it was once owned by the ornithologist George Edwards, has since become the standard image of a dodo. It is housed in the Natural History Museum, London. The image shows a particularly fat bird and is the source for many other dodo illustrations.[50][51]
An Indian Mughal painting rediscovered in the Hermitage Museum, St. Petersburg, in 1955 shows a dodo along with native Indian birds.[52] It depicts a slimmer, brownish bird, and its discoverer Aleksander Iwanow and British palaeontologist Julian Hume regarded it as one of the most accurate depictions of the living dodo; the surrounding birds are clearly identifiable and depicted with appropriate colouring.[53] It is believed to be from the 17th century and has been attributed to the Mughal painterUstad Mansur. The bird depicted probably lived in the menagerie of the Mughal EmperorJahangir, located in Surat, where the English traveller Peter Mundy also claimed to have seen two dodos sometime between 1628 and 1633.[54][23] In 2014, another Indian illustration of a dodo was reported, but it was found to be derivative of an 1836 German illustration.[55]
All post-1638 depictions appear to be based on earlier images, around the time reports mentioning dodos became rarer. Differences in the depictions led ornithologists such as Anthonie Cornelis Oudemans and Masauji Hachisuka to speculate about sexual dimorphism, ontogenic traits, seasonal variation, and even the existence of different species, but these theories are not accepted today. Because details such as markings of the beak, the form of the tail feathers, and colouration vary from account to account, it is impossible to determine the exact morphology of these features, whether they signal age or sex, or if they even reflect reality.[56] Hume argued that the nostrils of the living dodo would have been slits, as seen in the Gelderland, Cornelis Saftleven, Savery's Crocker Art Gallery, and Mansur images. According to this claim, the gaping nostrils often seen in paintings indicate that taxidermy specimens were used as models.[23] Most depictions show that the wings were held in an extended position, unlike flighted pigeons, but similar to ratites such as the ostrich and kiwi.[21]
Little is known of the behaviour of the dodo, as most contemporary descriptions are very brief. Based on weight estimates, it has been suggested the male could reach the age of 21, and the female 17.[39] Studies of the cantilever strength of its leg bones indicate that it could run quite fast.[40] The legs were robust and strong to support the bulk of the bird, and also made it agile and manoeuvrable in the dense, pre-human landscape. Though the wings were small, well-developed muscle scars on the bones show that they were not completely vestigial, and may have been used for display behaviour and balance; extant pigeons also use their wings for such purposes.[21] Unlike the Rodrigues solitaire, there is no evidence that the dodo used its wings in intraspecific combat. Though some dodo bones have been found with healed fractures, it had weak pectoral muscles and more reduced wings in comparison. The dodo may instead have used its large, hooked beak in territorial disputes. Since Mauritius receives more rainfall and has less seasonal variation than Rodrigues, which would have affected the availability of resources on the island, the dodo would have less reason to evolve aggressive territorial behaviour. The Rodrigues solitaire was therefore probably the more aggressive of the two.[57] In 2016, the first 3D endocast was made from the brain of the dodo; the brain-to-body-size ratio was similar to that of modern pigeons, indicating that dodos were probably equal in intelligence.[58]
1601 map of a bay on Mauritius; the small D on the far right side marks where dodos were found
The preferred habitat of the dodo is unknown, but old descriptions suggest that it inhabited the woods on the drier coastal areas of south and west Mauritius. This view is supported by the fact that the Mare aux Songes swamp, where most dodo remains have been excavated, is close to the sea in south-eastern Mauritius.[59] Such a limited distribution across the island could well have contributed to its extinction.[60] A 1601 map from the Gelderland journal shows a small island off the coast of Mauritius where dodos were caught. Julian Hume has suggested this island was l'île aux BenitiersinTamarin Bay, on the west coast of Mauritius.[61][47] Subfossil bones have also been found inside caves in highland areas, indicating that it once occurred on mountains. Work at the Mare aux Songes swamp has shown that its habitat was dominated by tambalacoque and Pandanus trees and endemic palms.[38] The near-coastal placement and wetness of the Mare aux Songes led to a high diversity of plant species, whereas the surrounding areas were drier.[62]
A 1631 Dutch letter (long thought lost, but rediscovered in 2017) is the only account of the dodo's diet, and also mentions that it used its beak for defence. The document uses word-play to refer to the animals described, with dodos presumably being an allegory for wealthy mayors:[66]
The mayors are superb and proud. They presented themselves with an unyielding, stern face and wide open mouth, very jaunty and audacious of gait. They did not want to budge before us; their war weapon was the mouth, with which they could bite fiercely. Their food was raw fruit; they were not dressed very well, but were rich and fat, therefore we brought many of them on board, to the contentment of us all.[66]
In addition to fallen fruits, the dodo probably subsisted on nuts, seeds, bulbs, and roots.[67] It has also been suggested that the dodo might have eaten crabs and shellfish, like their relatives the crowned pigeons. Its feeding habits must have been versatile, since captive specimens were probably given a wide range of food on the long sea journeys.[68] Oudemans suggested that as Mauritius has marked dry and wet seasons, the dodo probably fattened itself on ripe fruits at the end of the wet season to survive the dry season, when food was scarce; contemporary reports describe the bird's "greedy" appetite. The Mauritian ornithologist France Staub suggested in 1996 that they mainly fed on palm fruits, and he attempted to correlate the fat-cycle of the dodo with the fruiting regime of the palms.[30]
Skeletal elements of the upper jaw appear to have been rhynchokinetic (movable in relation to each other), which must have affected its feeding behaviour. In extant birds, such as frugivorous (fruit-eating) pigeons, kinetic premaxillae help with consuming large food items. The beak also appears to have been able to withstand high force loads, which indicates a diet of hard food.[21] Examination of the brain endocast found that though the brain was similar to that of other pigeons in most respects, the dodo had a comparatively large olfactory bulb. This gave the dodo a good sense of smell, which may have aided in locating fruit and small prey.[58]
Several contemporary sources state that the dodo used Gastroliths (gizzard stones) to aid digestion. The English writer Sir Hamon L'Estrange witnessed a live bird in London and described it as follows:
About 1638, as I walked London streets, I saw the picture of a strange looking fowle hung out upon a clothe and myselfe with one or two more in company went in to see it. 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 more erect shape, coloured before like the breast of a young cock fesan, and on the back of a dunn or dearc 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, whereof hee gave it many in our sight, some as big as nutmegs, and the keeper told us that she eats them (conducing to digestion), and though I remember not how far the keeper was questioned therein, yet I am confident that afterwards she cast them all again.[69]
It is not known how the young were fed, but related pigeons provide crop milk. Contemporary depictions show a large crop, which was probably used to add space for food storage and to produce crop milk. It has been suggested that the maximum size attained by the dodo and the solitaire was limited by the amount of crop milk they could produce for their young during early growth.[70]
In 1973, the tambalacoque, also known as the dodo tree, was thought to be dying out on Mauritius, to which it is endemic. There were supposedly only 13 specimens left, all estimated to be about 300 years old. Stanley Temple hypothesised that it depended on the dodo for its propagation, and that its seeds would germinate only after passing through the bird's digestive tract. He claimed that the tambalacoque was now nearly coextinct because of the disappearance of the dodo.[71] Temple overlooked reports from the 1940s that found that tambalacoque seeds germinated, albeit very rarely, without being abraded during digestion.[72] Others have contested his hypothesis and suggested that the decline of the tree was exaggerated or seeds were also distributed by other extinct animals such as Cylindraspistortoises, fruit bats, or the broad-billed parrot.[73] According to Wendy Strahm and Anthony Cheke, two experts in the ecology of the Mascarene Islands, the tree, while rare, has germinated since the demise of the dodo and numbers several hundred, not 13 as claimed by Temple, hence, discrediting Temple's view as to the dodo and the tree's sole survival relationship.[74]
The Brazilian ornithologist Carlos Yamashita suggested in 1997 that the broad-billed parrot may have depended on dodos and Cylindraspis tortoises to eat palm fruits and excrete their seeds, which became food for the parrots. Anodorhynchus macaws depended on now-extinct South Americanmegafauna in the same way, but now rely on domesticated cattle for this service.[75]
Reproduction and development
Replica of an alleged dodo egg in a reconstructed nest, East London Museum
As it was flightless and terrestrial and there were no mammalian predators or other kinds of natural enemy on Mauritius, the dodo probably nested on the ground.[76] The account by François Cauche from 1651 is the only description of the egg and the call:
I have seen in Mauritius birds bigger than a Swan, without feathers on the body, which is covered with a black down; the hinder part is round, the rump adorned with curled feathers as many in number as the bird is years old. In place of wings they have feathers like these last, black and curved, without webs. They have no tongues, the beak is large, curving a little downwards; their legs are long, scaly, with only three toes on each foot. It has a cry like a gosling, and is by no means so savoury to eat as the Flamingos and Ducks of which we have just spoken. They only lay one egg which is white, the size of a halfpenny roll, by the side of which they place a white stone the size of a hen's egg. They lay on grass which they collect, and make their nests in the forests; if one kills the young one, a grey stone is found in the gizzard. We call them Oiseaux de Nazaret. The fat is excellent to give ease to the muscles and nerves.[6]
Thin sections of hindlimb bones showing stages of the growth series
Diagram showing life history events of a dodo based on histology and accounts
Cauche's account is problematic, since it also mentions that the bird he was describing had three toes and no tongue, unlike dodos. This led some to believe that Cauche was describing a new species of dodo ("Didus nazarenus"). The description was most probably mingled with that of a cassowary, and Cauche's writings have other inconsistencies.[77] A mention of a "young ostrich" taken on board a ship in 1617 is the only other reference to a possible juvenile dodo.[78] An egg claimed to be that of a dodo is stored in the East London Museum in South Africa. It was donated by the South African museum official Marjorie Courtenay-Latimer, whose great aunt had received it from a captain who claimed to have found it in a swamp on Mauritius. In 2010, the curator of the museum proposed using genetic studies to determine its authenticity.[79] It may instead be an aberrant ostrich egg.[32]
Because of the possible single-egg clutch and the bird's large size, it has been proposed that the dodo was K-selected, meaning that it produced few altricial offspring, which required parental care until they matured. Some evidence, including the large size and the fact that tropical and frugivorous birds have slower growth rates, indicates that the bird may have had a protracted development period.[39] The fact that no juvenile dodos have been found in the Mare aux Songes swamp may indicate that they produced little offspring, that they matured rapidly, that the breeding grounds were far away from the swamp, or that the risk of miring was seasonal.[80]
A 2017 study examined the histologyofthin-sectioned dodo bones, modern Mauritian birds, local ecology, and contemporary accounts, to recover information about the life history of the dodo. The study suggested that dodos bred around August, after having potentially fattened themselves, corresponding with the fat and thin cycles of many vertebrates of Mauritius. The chicks grew rapidly, reaching robust, almost adult, sizes, and sexual maturity before Austral summer or the cyclone season. Adult dodos which had just bred moulted after Austral summer, around March. The feathers of the wings and tail were replaced first, and the moulting would have completed at the end of July, in time for the next breeding season. Different stages of moulting may also account for inconsistencies in contemporary descriptions of dodo plumage.[81]
Relationship with humans
1648 engraving showing the killing of dodos (centre left, erroneously depicted as penguin-like) and other animals now extinct from Mauritius
Mauritius had previously been visited by Arab vessels in the Middle Ages and Portuguese ships between 1507 and 1513, but was settled by neither. No records of dodos by these are known, although the Portuguese name for Mauritius, "Cerne (swan) Island", may have been a reference to dodos.[82] The Dutch Empire acquired Mauritius in 1598, renaming it after Maurice of Nassau, and it was used for the provisioning of trade vessels of the Dutch East India Company henceforward.[83] The earliest known accounts of the dodo were provided by Dutch travellers during the Second Dutch Expedition to Indonesia, led by admiralJacob van Neck in 1598. They appear in reports published in 1601, which also contain the first published illustration of the bird.[84] Since the first sailors to visit Mauritius had been at sea for a long time, their interest in these large birds was mainly culinary. The 1602 journal by Willem Van West-Zanen of the ship Bruin-Vis mentions that 24–25 dodos were hunted for food, which were so large that two could scarcely be consumed at mealtime, their remains being preserved by salting.[85] An illustration made for the 1648 published version of this journal, showing the killing of dodos, a dugong, and possibly Mascarene grey parakeets, was captioned with a Dutch poem,[86] here in Hugh Strickland's 1848 translation:
For food the seamen hunt the flesh of feathered fowl,
They tap the palms, and round-rumped dodos they destroy,
The parrot's life they spare that he may peep and howl,
And thus his fellows to imprisonment decoy.[87]