Araguaian river dolphin

The Araguaian river dolphin or Araguaian boto (Inia araguaiaensis) is a South American river dolphin population whose identification as a species was announced in 2014. It is native to the Araguaia-Tocantins basin of Brazil.

Discovery
The recognition of I. araguaiaensis as a separate species was announced on January 22, 2014. It was distinguished from other members of Inia on the basis of nuclear microsatellite and mitochondrial DNA data as well as differences in skull morphology (they generally have wider skulls). It also differs from the Amazon and Bolivian river dolphins in the number of teeth per hemimandible (24–28 versus 25–29 and 31–35, respectively). It is the first new river dolphin species to be described since 1918.

Description                                       

Close relative Inia geoffrensis

Members of the genus are gray to pink in color and have a body length range from 1.53 to 2.6 m (5.0 to 8.5 ft). They have a dorsal ridge rather than a fin. Their neck vertebrae are unfused, allowing them to turn their heads sharply. Like other river dolphins, I. araguaiaensis has a prominent forehead and a much longer snout than those of most marine dolphins, as well as smaller eyes than marine dolphins. Because their aquatic environment is often turbid, their vision is not as well developed. River dolphins tend to be less active than marine dolphins. They feed mainly on fish, aided by echolocation.

Taxonomy

This species is most closely related to the Amazon river dolphin (Inia geoffrensis), from which it is believed to have split about 2.08 million years (Ma) ago, on the basis of mitochondrial DNA sequence comparisons. The time of divergence corresponds to the time the Amazon and Araguaia-Tocantins river basins became separated, implying vicariant speciation. Major rapids in the lower Tocantins River (into which the Araguaia River flows) are thought to have contributed to isolating the two species, as the Pará River (into which the Tocantins flows) connects with the Amazon River.

non-South Asian river dolphins	South American Inia   Inia araguaiaensis (Araguaian river dolphin) Inia geoffrensis (Amazon river dolphin) Inia boliviensis (Bolivian river dolphin) Pontoporia blainvillei (La Plata dolphin) †Lipotes vexillifer (baiji or Yangtse river dolphin)

The estimated times of divergence with I. boliviensis, P. blainvillei and L. vexillifer are 2.9, 12.0 and 16.2 Ma ago, respectively.

Conservation issues

The total population of the species is estimated to be of the order of 600 to 1500 individuals, and genetic diversity is limited. The ecology of its habitat has been adversely affected by agricultural, ranching and industrial activities, as well as by the use of dams for hydroelectric power. The inhabited section of the Araguaia River probably extends over about 1500 km out of a total length of 2110 km. The Tocantins River habitat is fragmented by six hydroelectric dams, so the population there is at particular risk. The authors of the discovery paper regard its probable eventual IUCN status to be Vulnerable or worse.

Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Subclass:	Eutheria
Order:	Cetacea
Suborder:	Odontoceti
Superfamily:	Inioidea
Family:	Iniidae
Genus:	Inia
Species:	I. araguaiaensis
Binomial name
Inia araguaiaensis Hrbek et al., 2014
Inia spp. ranges. I. araguaiaensis is in blue at right; I. geoffrensis and I. boliviensis are light green and purple, respectively.

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Blue whale

The blue whale (Balaenoptera musculus) is a marine mammal belonging to the baleen whales (Mysticeti). At 30 metres (98 ft) in length and 170 tonnes (190 short tons) or more in weight, it is the largest known animal ever to have existed.

Long and slender, the blue whale's body can be various shades of bluish-grey dorsally and somewhat lighter underneath. There are at least three distinct subspecies: B. m. musculusof the North Atlantic and North Pacific, B. m. intermedia of the Southern Ocean and B. m. brevicauda (also known as the pygmy blue whale) found in the Indian Ocean and South Pacific Ocean. B. m. indica, found in the Indian Ocean, may be another subspecies. As with other baleen whales, its diet consists almost exclusively of small crustaceans known as krill.

Blue whales were abundant in nearly all the oceans on Earth until the beginning of the twentieth century. For over a century, they were hunted almost to extinction by whalers until protected by the international community in 1966. A 2002 report estimated there were 5,000 to 12,000 blue whales worldwide, located in at least five groups. More recent research into the Pygmy subspecies suggests this may be an underestimate. Before whaling, the largest population was in the Antarctic, numbering approximately 239,000 (range 202,000 to 311,000). There remain only much smaller (around 2,000) concentrations in eacha of the eastern North Pacific, Antarctic, and Indian Ocean groups. There are two more groups in the North Atlantic, and at least two in the Southern Hemisphere.


Taxonomy

Blue whales are rorquals (family Balaenopteridae), a family that includes the humpback whale, the fin whale, Bryde's whale, the sei whale, and the minke whale. The familyBalaenopteridae is believed to have diverged from the other families of the suborder Mysticetias long ago as the middle Oligocene. It is not known when the members of those families diverged from each other.

The blue whale is usually classified as one of eight species in the genus Balaenoptera; one authority places it in a separate monotypic genus, Sibbaldus, but this is not accepted elsewhere. DNA sequencing analysis indicates that the blue whale is phylogeneticallycloser to the sei whale (Balaenoptera borealis) and Bryde's whale (Balaenoptera brydei) than to other Balaenoptera species, and closer to the humpback whale (Megaptera) and the gray whale (Eschrichtius) than to the minke whales (Balaenoptera acutorostrata and Balaenoptera bonaerensis). If further research confirms these relationships, it will be necessary to reclassify the rorquals.

There have been at least 11 documented cases of blue/fin hybrid adults in the wild. Arnason and Gullberg describe the genetic distance between a blue and a fin as about the same as that between a human and a gorilla. Researchers working off Fiji believe they photographed a hybrid humpback/blue whale.

The first published description of the blue whale comes from Robert Sibbald's Phalainologia Nova (1694). In September 1692, Sibbald found a blue whale that had stranded in the Firth of Forth—a male 78-feet-long—which had "black, horny plates" and "two large apertures approaching a pyramid in shape".

The specific name musculus is Latin and could mean "muscle", but it can also be interpreted as "little mouse". Carl Linnaeus, who named the species in his seminal Systema Naturae of 1758, would have known this and may have intended the ironic double meaning. Herman Melville called this species sulphur-bottom in his novel Moby-Dick due to an orange-brown or yellow tinge on the underparts from diatom films on the skin. Other common names for the blue whale have included Sibbald's rorqual (after Sibbald, who first described the species), the great blue whale and the great northern rorqual. These names have now fallen into disuse. The first known usage of the term blue whale was in Melville's Moby-Dick, which only mentions it in passing and does not specifically attribute it to the species in question. The name was really derived from the Norwegian blåhval, coined by Svend Foyn shortly after he had perfected the harpoon gun; the Norwegian scientist G. O. Sars adopted it as the Norwegian common name in 1874.

Authorities classify the species into three or four subspecies: B. m. musculus, the northern blue whale consisting of the North Atlantic and North Pacific populations, B. m. intermedia, the southern blue whale of the Southern Ocean, B. m. brevicauda, the pygmy blue whale found in the Indian Ocean and South Pacific, and the more problematic B. m. indica, the great Indian rorqual, which is also found in the Indian Ocean and, although described earlier, may be the same subspecies as B. m. brevicauda.

Description and behaviour

A blue whale lifting its tail flukes

Adult blue whale

The blue whale has a long tapering body that appears stretched in comparison with the stockier build of other whales. The head is flat, U-shaped and has a prominent ridge running from theblowhole to the top of the upper lip. The front part of the mouth is thick with baleen plates; around 300 plates (each around one metre (3.2 ft) long) hang from the upper jaw, running 0.5 m (1.6 ft) back into the mouth. Between 70 and 118 grooves (called ventral pleats) run along the throat parallel to the body length. These pleats assist with evacuating water from the mouth after lunge feeding (see feeding below).

The dorsal fin is small, ranging in height from 8–70 centimeters (3.1–28 in) (usually 20–40 centimeters (7.9–16 in)) and averaging about 28 centimetres (11 in). It is visible only briefly during the dive sequence. Located around three-quarters of the way along the length of the body, it varies in shape from one individual to another; some only have a barely perceptible lump, but others may have prominent and falcate (sickle-shaped) dorsals. When surfacing to breathe, the blue whale raises its shoulder and blowhole out of the water to a greater extent than other large whales, such as the fin or sei whales. Observers can use this trait to differentiate between species at sea. Some blue whales in the North Atlantic and North Pacific raise their tail fluke when diving. When breathing, the whale emits a spectacular vertical single-column spout up to 12 metres (39 ft), typically 9 metres (30 ft). Its lung capacity is 5,000 litres (1320 U.S. gallons). Blue whales have twin blowholes shielded by a large splashguard.

The flippers are 3–4 metres (9.8–13 ft) long. The upper sides are grey with a thin white border; the lower sides are white. The head and tail fluke are generally uniformly grey. The whale's upper parts, and sometimes the flippers, are usually mottled. The degree of mottling varies substantially from individual to individual. Some may have a uniform slate-grey color, but others demonstrate a considerable variation of dark blues, greys and blacks, all tightly mottled.

Blue whales can reach speeds of 50 kilometres per hour (31 mph) over short bursts, usually when interacting with other whales, but 20 kilometres per hour (12 mph) is a more typical traveling speed. When feeding, they slow down to 5 kilometres per hour (3.1 mph).

Blue whales most commonly live alone or with one other individual. It is not known how long traveling pairs stay together. In locations where there is a high concentration of food, as many as 50 blue whales have been seen scattered over a small area. They do not form the large, close-knit groups seen in other baleen species.

Aerial view of a blue whale showing both pectoral fins

Size

The blow of a blue whale

The small dorsal fin of this blue whale is just visible on the far left.

The blue whale is the largest animal ever known to have lived. The largest known dinosaur of theMesozoic Era was Argentinosaurus, which is estimated to have weighed up to 90 metric tons (99 short tons).

Blue whales are difficult to weigh because of their size. As is the case with most large whales targeted by whalers, adult blue whales have never been weighed whole, but cut up into manageable pieces first. This caused an underestimate of the total weight of the whale, due to the loss of blood and other fluids. As a whole, blue whales from the Northern Atlantic and Pacific appear to be smaller on average than those from sub-Antarctic waters. Nevertheless, measurements between 150–170 metric tons (170–190 short tons) were recorded of animals up to 27 metres (89 ft) in length. The weight of an individual 30 metres (98 ft) long is believed by the American National Marine Mammal Laboratory (NMML) to be in excess of 180 metric tons (200 short tons). The largest blue whale accurately weighed by NMML scientists to date was a female that weighed 177 metric tons (195 short tons).

There is some uncertainty about the biggest blue whale ever found, as most data came from blue whales killed in Antarctic waters during the first half of the twentieth century, which were collected by whalers not well-versed in standard zoological measurement techniques. The heaviest whale ever recorded weighed in at approximately 190 metric tons (210 short tons).The longest whales ever recorded were two females measuring 33.6 metres (110 ft) and 33.3 metres (109 ft), although in neither of these cases was the piecemeal weight gathered.The longest whale measured by scientists at the NMML was a 29.9 metres (98 ft),female caught in the Antarctic by Japanese whalers in 1946–47. Lieut. Quentin R. Walsh, USCG, while acting as whaling inspector of the factory ship Ulysses, verified the measurement of a 30 m (98 ft) pregnant blue whale caught in the Antarctic in the 1937–38 season. The longest reported in the North Pacific was a 27.1 metres (89 ft) female taken by Japanese whalers in 1959, and the longest reported in the North Atlantic was a 28.1 metres (92 ft) female caught in the Davis Strait.

Due to its large size, several organs of the blue whale are the largest in the animal kingdom. A blue whale's tongue weighs around 2.7 metric tons (3.0 short tons) and, when fully expanded, its mouth is large enough to hold up to 90 metric tons (99 short tons) of food and water. Despite the size of its mouth, the dimensions of its throat are such that a blue whale cannot swallow an object wider than a beach ball. Its heart weighs 600 kilograms (1,300 lb) and is the largest known in any animal. A blue whale'sthoracic aorta is estimated to be 23 centimetres (9.1 in) in diameter. During the first seven months of its life, a blue whale calf drinks approximately 400 litres (110 US gal) of milk every day. Blue whale calves gain weight quickly, as much as 90 kilograms (200 lb) every 24 hours. Even at birth, they weigh up to 2,700 kilograms (6,000 lb)—the same as a fully grown hippopotamus. Blue whales have relatively small brains, only about 6.92 kilograms (15.26 lb) , about 0.007% of its body weight. The blue whale penis is the largest penis of any living organism. The reported average length varies but is usually mentioned to have an average penis length of 8 feet (2.4 m) to 10 feet (3.0 m).

A blue whale skull measuring 19 feet (5.79 m) in the collections of the Smithsonian Museum of Natural History

Feeding

Blue whales feed almost exclusively on krill, though they also take small numbers of copepods.The species of this zooplankton eaten by blue whales varies from ocean to ocean. In the North Atlantic, Meganyctiphanes norvegica, Thysanoessa raschii, Thysanoessa inermis and Thysanoessa longicaudata are the usual food;in the North Pacific, Euphausia pacifica, Thysanoessa inermis, Thysanoessa longipes, Thysanoessa spinifera, Nyctiphanes symplex and Nematoscelis megalops; and in the Southern Hemisphere, Euphausia superba, Euphausia crystallorophias,Euphausia valentini, and Nyctiphanes australis.

An adult blue whale can eat up to 40 million krill in a day. The whales always feed in the areas with the highest concentration of krill, sometimes eating up to 3,600 kilograms (7,900 lb) of krill in a single day. The daily energy requirement of an adult blue whale is in the region of 1.5 million kilocalories. Their feeding habits are seasonal. Blue whales gorge on krill in the rich waters of the Antarctic before migrating to their breeding grounds in the warmer, less-rich waters nearer the equator. The blue whale can take in up to 90 times as much energy as it expends, allowing it to build up considerable energy reserves.

Because krill move, blue whales typically feed at depths of more than 100 metres (330 ft) during the day and only surface-feed at night. Dive times are typically 10 minutes when feeding, though dives of up to 20 minutes are common. The longest recorded dive is 36 minutes. The whale feeds by lunging forward at groups of krill, taking the animals and a large quantity of water into its mouth. The water is then squeezed out through the baleen plates by pressure from the ventral pouch and tongue. Once the mouth is clear of water, the remaining krill, unable to pass through the plates, are swallowed. The blue whale also incidentally consumes small fish, crustaceans and squid caught up with krill.

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Mammoth

A mammoth is any species of the extinct genus Mammuthus, proboscideans commonly equipped with long, curved tusks and, in northern species, a covering of longhair. They lived from the Pliocene epoch (from around 5 million years ago) into theHolocene at about 4,500 years ago in Africa, Europe, Asia, and North America. They were members of the family Elephantidae which contains, along with mammoths, the two genera of modern elephants and their ancestors.

Evolution

The earliest known proboscideans, the clade which contains the elephants, existed about 55 million years ago around the Tethys Sea area. The closest relatives of the Proboscidea are the sirenians and the hyraxes. The family Elephantidae is known to have existed six million years ago in Africa, and includes the living elephants and the mammoths. Among many now extinct clades, the mastodon is only a distant relative of the mammoths, and part of the separate Mammutidae family which diverged 25 million years before the mammoths evolved. The following cladogram shows the placement of the genus Mammuthus among other proboscideans, based on hyoid characteristics:

	Mammut (Mastodon) Gomphotherium Stegodon Loxodonta (African elephant) Elephas (Asian elephant) Mammuthus (Mammoth)

Comparison of a woolly mammoth (L) and an American mastodon (R).

Since many remains of each species of mammoth are known from several localities, it is possible to reconstruct the evolutionary history of the genus through morphological studies. Mammoth species can be identified from the number of enamel ridges on their molars; the primitive species had few ridges, and the amount increased gradually as new species evolved and replaced the former ones. At the same time, the crowns of the teeth became longer, and the skulls become higher from top to bottom and shorter from the back to the front over time to accommodate this.

The first known members of the genus Mammuthus are the African species M. subplanifrons from the Pliocene and M. africanavus from the Pleistocene. The former is thought to be the ancestor of later forms. Mammoths entered Europe around 3 million years ago; the earliest known type has been named M. rumanus, which spread across Europe and China. Only its molars are known, which show it had 8-10 enamel ridges. A population evolved 12-14 ridges and split off from and replaced the earlier type, becoming M. meridionalis. In turn, this species was replaced by the steppe mammoth, M. trogontherii, with 18-20 ridges, which evolved in East Asia ca. 1 million years ago. Mammoths derived from M. trogontherii evolved molars with 26 ridges 200,000 years ago in Siberia, and became the woolly mammoth, M. primigenius. The Columbian mammoth, M. columbi, also evolved from a population of M. trogontherii which had entered North America. A 2011 genetic study showed that two examined specimens of the Columbian mammoth were grouped within a subclade of woolly mammoths. This suggests that the two populations interbred and produced fertile offspring. It also suggested that a North American form known as "M. jeffersonii" may be a hybrid between the two species.

From 3 Ma to the late Pleistocene, mammoths in continental Eurasia has undergone a major transformation, including a shortening and heightening of the cranium and mandible, increase in molar hypsodonty index, increase in plate number, and thinning of dental enamel. Due to this drastic change in physical appearance, people started grouping European mammoths separately into distinguishable clusters:

1) Early Pleistocene Mammuthus meridionalis

2) Middle Pleistocene Mammuthus trogontherii

3) Late Pleistocene Mammuthus primigenius

There is speculation to how variation occurred within the three chronospecies. Deviations in environment, climate change, and migration have also played a role in the evolutionary process of the mammoths. Take M. primigenius for example, during their lifespan, woolly mammoths would have lived in opened grassland biomes. The cool steppe-tundra of the Northern Hemisphere was the ideal place for mammoths to thrive because of the resources it supplied. Of course, with the warmings during the ice age, climate would also change the landscape and what was available to the mammoths altered drastically.

Description

Restoration of a steppe mammoth

Like their modern relatives, mammoths were quite large. The largest known species reached heights in the region of 4 m (13 ft) at the shoulder and weights up to 8 tonnes (9 short tons), while exceptionally large males may have exceeded 12 tonnes (13 short tons). However, most species of mammoth were only about as large as a modern Asian elephant (which are about 2.5m to 3m high at the shoulder, and rarely exceeding 5.4 tonnes). Both sexes bore tusks. A first, small set appeared at about the age of six months and these were replaced at about 18 months by the permanent set. Growth of the permanent set was at a rate of about 1 to 6 inches (2.5 to 15 cm) per year.

Based on studies of their close relatives, the modern elephants, mammoths probably had agestation period of 22 months, resulting in a single calf being born. Their social structure was probably the same as that of African and Asian elephants, with females living in herds headed by a matriarch, whilst bulls lived solitary lives or formed loose groups after sexual maturity.

Scientists discovered and studied the remainders of a mammoth calf and found that the fat in a mammoth plays a major role to the mammoth's form and ability. One of the major roles of mammoth fat is their ability to store large amounts of nutrients to accommodate to the colder climate they live in. The fat also allowed the mammoths to increase their muscle mass, allowing the mammoths to fight against enemies and live longer.

Extinction

Lyuba, a mummified woolly mammoth, at the Field Museum of Natural History inChicago

The woolly mammoth (M. primigenius) was the last species of the genus. Most populations of the woolly mammoth in North America and Eurasia, as well as all the Columbian mammoths(M. columbi) in North America, died out around the time of the last glacial retreat, as part of amass extinction of megafauna in northern Eurasia and the Americas. Until recently, the last woolly mammoths were generally assumed to have vanished from Europe and southern Siberia about 12,000 years ago, but new findings show some were still present there about 10,000 years ago. Slightly later, the woolly mammoths also disappeared from continental northern Siberia. A small population survived on St. Paul Island, Alaska, up until 3750 BC, and the small mammoths of Wrangel Island survived until 1650 BC. Recent research of sediments in Alaska indicates mammoths survived on the American mainland until 10,000 years ago.

A definitive explanation for their extinction has yet to be agreed upon. The warming trend (Holocene) that occurred 12,000 years ago, accompanied by a glacial retreat and rising sea levels, has been suggested as a contributing factor. Forests replaced open woodlands and grasslands across the continent. The available habitat may have been reduced for some megafaunal species, such as the mammoth. However, such climate changes were nothing new; numerous very similar warming episodes had occurred previously within the ice age of the last several million years without producing comparable megafaunal extinctions, so climate alone is unlikely to have played a decisive role. The spread of advanced human hunters through northern Eurasia and the Americas around the time of the extinctions was a new development, and thus might have contributed significantly.

Whether the general mammoth population died out for climatic reasons or due to overhunting by humans is controversial. During the transition from the Late Pleistocene era to the Holocene era, there was shrinkage of the distribution of the mammoth because of the progressive warming at the end of the Pleistocene era resulted in change in the mammoth's environment. The mammoth steppe was a periglacial landscape with rich herb and grass vegetation that disappeared along with the mammoth because of environmental changes in the climate. Mammoths had moved to isolated spots in Eurasia, where they disappeared completely. Also, it is said that Late Paleolithic and Mesolithic human hunters may have affected the size of the last mammoth populations in Europe. There is evidence to suggest that humans did cause the mammoth extinction, although there is no definitive proof. It was found that humans living south of a mammoth steppe learned to adapt themselves to the harsher climates north of the steppe, where mammoths resided. It was concluded that if humans could survive the harsh north climate of that particular mammoth steppe that it was possible humans could hunt (and eventually extinguish) mammoths everywhere.</ref> Another theory suggests mammoths may have fallen victim to an infectious disease.</ref> A combination of climate change and hunting by humans may be a possible explanation for their extinction. Homo erectus is known to have consumed mammoth meat as early as 1.8 million years ago.This may mean only successful scavenging, rather than actual hunting. A site in Ukraine suggests Neanderthals built dwellings using mammoth bones. However, the American Institute of Biological Sciences also notes bones of dead elephants, left on the ground and subsequently trampled by other elephants, tend to bear marks resembling butchery marks, which have previously been misinterpreted as such by archaeologists.

Another theory said to be the cause of mammoths in Siberia, comes from the idea that many may have drowned. While traveling to the Northern River many of these mammoths broke through the ice and drowned. This also explains bones remains in the Arctic Coast and islands of the New Siberian Group.

Dwarfing occurred with the pygmy mammoth on the outer Channel Islands of California, but at an earlier period. Those animals were very likely killed by early Paleo-Native Americans, and habitat loss caused by a rising sea level that split Santa Rosae into the outer Channel Islands.

De-Extinction

As of 2014, there are ongoing projects such as that from Sooam attempting to recover the mammoth population. Similar to the method popularised in the film Jurassic Park, the projects are based on finding suitable DNA in frozen bodies. The next step is to recover and, if possible, combine the DNA with similar living animals such as the elephant, which may give birth to some mammoth-related or mammoth species.

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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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