Rodrigues Solitaire
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The Rodrigues solitaire (''Pezophaps solitaria'') is an
extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
flightless bird Flightless birds are birds that cannot Bird flight, fly, as they have, through evolution, lost the ability to. There are over 60 extant species, including the well-known ratites (ostriches, emus, cassowary, cassowaries, Rhea (bird), rheas, an ...
that was
endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
to the island of
Rodrigues Rodrigues ( ; Mauritian Creole, Creole: ) is a Autonomous administrative division, autonomous Outer islands of Mauritius, outer island of the Republic of Mauritius in the Indian Ocean, about east of Mauritius. It is part of the Mascarene Isl ...
, east of
Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...
in the Indian Ocean. Genetically within the family of pigeons and doves, it was most closely related to the also extinct
dodo The dodo (''Raphus cucullatus'') is an extinction, extinct flightless bird that was endemism, 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 flightles ...
of the nearby island
Mauritius Mauritius, officially the Republic of Mauritius, is an island country in the Indian Ocean, about off the southeastern coast of East Africa, east of Madagascar. It includes the main island (also called Mauritius), as well as Rodrigues, Ag ...
, the two forming the subfamily
Raphinae Columbidae is a bird family consisting of doves and pigeons. It is the only family in the order Columbiformes. These are stout-bodied birds with small heads, relatively short necks and slender bills that in some species feature fleshy ceres. ...
. The
Nicobar pigeon The Nicobar pigeon or Nicobar dove (''Caloenas nicobarica'', Car: ') is a bird found on small islands and in coastal regions from the Andaman and Nicobar Islands, India, east through the Indonesian Archipelago, to the Solomons and Palau. It is ...
is their closest living genetic relative. Rodrigues solitaires grew to the size of
swan Swans are birds of the genus ''Cygnus'' within the family Anatidae. The swans' closest relatives include the goose, geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe (biology) ...
s, and demonstrated pronounced
sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...
. Males were much larger than females and measured up to in height and in weight, contrasting with and for females. Its
plumage Plumage () is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, there can b ...
was grey and brown; the female was paler than the male. It had a black band at the base of its slightly hooked beak, and its neck and legs were long. Both sexes were highly
territorial A territory is an area of land, sea, or space, belonging or connected to a particular country, person, or animal. In international politics, a territory is usually a geographic area which has not been granted the powers of self-government, ...
, with large bony knobs on their wings that were used in combat. The Rodrigues solitaire laid a single egg that was incubated in turn by both sexes. Gizzard stones helped digest its food, which included fruit and seeds. First mentioned during the 17th century, the Rodrigues solitaire was described in detail by
François Leguat François Leguat (1637/1639 – September 1735) was a French explorer and naturalist. He was one of a small group of male French Protestant refugees who in 1691 settled on the then uninhabited island of Rodrigues in the western Indian Ocean. Th ...
, the leader of a group of
French Huguenot The Huguenots ( , ; ) are a Religious denomination, religious group of French people, French Protestants who held to the Reformed (Calvinist) tradition of Protestantism. The term, which may be derived from the name of a Swiss political leader, ...
refugees who were marooned on Rodrigues in 1691–1693. It was hunted by humans and introduced animals, and was extinct by the late 18th century. Apart from Leguat's account and drawing, and a few other contemporary descriptions, nothing was known about the bird until a few
subfossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
bones were found in a cave in 1786. Thousands of bones have subsequently been excavated. It is the only extinct bird with a
former constellation Former constellations are old historical Western constellations that for various reasons are no longer widely recognised or are not officially recognised by the International Astronomical Union (IAU). Prior to 1930, many of these defunct const ...
named after it,
Turdus Solitarius Turdus Solitarius (Latin for ''solitary thrush'') was a constellation created by French astronomer Pierre Charles Le Monnier in 1776 from stars of Hydra's tail. It was named after the Rodrigues solitaire, an extinct flightless bird that was ende ...
.


Taxonomy

The French explorer
François Leguat François Leguat (1637/1639 – September 1735) was a French explorer and naturalist. He was one of a small group of male French Protestant refugees who in 1691 settled on the then uninhabited island of Rodrigues in the western Indian Ocean. Th ...
was the first to refer to the bird as the "solitaire" (referring to its solitary habits), but it has been suggested that he borrowed the name from a 1689
tract Tract may refer to: Geography and real estate * Housing tract, an area of land that is subdivided into smaller individual lots * Land lot or tract, a section of land * Census tract, a geographic region defined for the purpose of taking a census ...
by his sponsor Marquis Henri Duquesne, which used the name "solitaire" in reference to the
Réunion ibis The Réunion ibis or Réunion sacred ibis (''Threskiornis solitarius'') is an list of extinct birds, extinct species of ibis that was endemic to the volcanic island of Réunion in the Indian Ocean. The first subfossil remains were found in 1974 ...
. The bird was first scientifically named in 1789 as a
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of dodo (''Didus solitarius'', based on Leguat's description) by the German naturalist
Johann Friedrich Gmelin Johann Friedrich Gmelin (8 August 1748 – 1 November 1804) was a German natural history, naturalist, chemist, botanist, entomologist, herpetologist, and malacologist. Education Johann Friedrich Gmelin was born as the eldest son of Philipp F ...
in the thirteenth edition of ''
Systema Naturae ' (originally in Latin written ' with the Orthographic ligature, ligature æ) is one of the major works of the Sweden, Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the syste ...
''. In 1786, subfossil Rodrigues solitaire bones encrusted in
stalagmite A stalagmite (, ; ; ) is a type of rock formation that rises from the floor of a cave due to the accumulation of material deposited on the floor from ceiling drippings. Stalagmites are typically composed of calcium carbonate, but may consist ...
were discovered in a cave and sent to the French naturalist
Georges Cuvier Jean Léopold Nicolas Frédéric, baron Cuvier (23 August 1769 – 13 May 1832), known as Georges Cuvier (; ), was a French natural history, naturalist and zoology, zoologist, sometimes referred to as the "founding father of paleontology". Cuv ...
in about 1830. For unknown reasons, he stated they had recently been found on
Mauritius Mauritius, officially the Republic of Mauritius, is an island country in the Indian Ocean, about off the southeastern coast of East Africa, east of Madagascar. It includes the main island (also called Mauritius), as well as Rodrigues, Ag ...
, which caused confusion, until they were compared with other bones from Rodrigues that were found to belong to the same species. The English naturalists
Hugh Edwin Strickland Hugh Edwin Strickland (2 March 1811 – 14 September 1853) was an English geologist, ornithology, ornithologist, naturalist and systematist. Through the British Association, he proposed a series of rules for the nomenclature of organisms in zool ...
and Alexander Gordon Melville suggested the common descent of the Rodrigues solitaire and the
dodo The dodo (''Raphus cucullatus'') is an extinction, extinct flightless bird that was endemism, 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 flightles ...
in 1848. They dissected the only known dodo specimen with soft tissue, comparing it with the few Rodrigues solitaire remains then available. Strickland stated that, although not identical, these birds shared many distinguishing features in the leg bones otherwise only known in
pigeon Columbidae is a bird family consisting of doves and pigeons. It is the only family in the order Columbiformes. These are stout-bodied birds with small heads, relatively short necks and slender bills that in some species feature fleshy ceres. ...
s. The fact that the Rodrigues solitaire laid only one egg, fed on fruits, was
monogamous Monogamy ( ) is a relationship of two individuals in which they form a mutual and exclusive intimate partnership. Having only one partner at any one time, whether for life or serial monogamy, contrasts with various forms of non-monogamy (e.g. ...
and cared for its nestlings also supported this relationship. Strickland recognised its generic distinction and named the new
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
''Pezophaps'', from
ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
' ( 'pedestrian') and ' ( 'pigeon'). The differences between the sexes of the bird were so large that Strickland thought they belonged to two species, naming the smaller female bird ''Pezophaps minor''. Additional subfossils were recovered during the 1860s, but more complete remains were found during the 1874 transit of Venus, since an observation station was located on the island. Many of these excavations were requested by the English ornithologists (and brothers)
Alfred Alfred may refer to: Arts and entertainment *''Alfred J. Kwak'', Dutch-German-Japanese anime television series * ''Alfred'' (Arne opera), a 1740 masque by Thomas Arne * ''Alfred'' (Dvořák), an 1870 opera by Antonín Dvořák *"Alfred (Interlu ...
and
Edward Newton Sir Edward Newton (10 November 1832 – 25 April 1897) was a British colonial administrator and ornithologist. He was born at Elveden Hall, Suffolk the sixth and youngest son of William Newton (MP for Ipswich), William Newton, MP. He was the ...
, who used them to describe the
osteology Osteology () is the scientific study of bones, practiced by osteologists . A subdiscipline of anatomy, anthropology, archaeology and paleontology, osteology is the detailed study of the structure of bones, skeletal elements, teeth, microbone mo ...
of the bird in detail. Thousands of bones were excavated, and mounted skeletons were composed from the remains of several specimens. Study of skeletal features by the Newtons indicated that the solitaire was morphologically intermediate between the dodo and ordinary pigeons, but differed from them in its unique
carpal The carpal bones are the eight small bones that make up the wrist (carpus) that connects the hand to the forearm. The terms "carpus" and "carpal" are derived from the Latin carpus and the Greek καρπός (karpós), meaning "wrist". In huma ...
knob. Some scientists believed that
Réunion Réunion (; ; ; known as before 1848) is an island in the Indian Ocean that is an overseas departments and regions of France, overseas department and region of France. Part of the Mascarene Islands, it is located approximately east of the isl ...
was home not only to a white dodo, but also to a white bird similar to the Rodrigues solitaire, both of which are now believed to be misinterpretations of old reports of the Réunion ibis. An atypical 17th-century description of a dodo and bones found on
Rodrigues Rodrigues ( ; Mauritian Creole, Creole: ) is a Autonomous administrative division, autonomous Outer islands of Mauritius, outer island of the Republic of Mauritius in the Indian Ocean, about east of Mauritius. It is part of the Mascarene Isl ...
, now known to have belonged to the Rodrigues solitaire, led the British taxidermist
Abraham Dee Bartlett Abraham Dee Bartlett (27 October 1812 – 7 May 1897) was a British taxidermist and an expert on captive animals. A superintendent of the London Zoo, he was a prominent observer of animal life and a zoologist who became a popular authority on wi ...
to name a new species, ''Didus nazarenus''; it is now a
junior synonym In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...
of this species. At one point it was suggested that the skeleton of this species is the best described after that of
human Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...
s. In spite of the evidence, some later scholars doubted Leguat's story, and the existence of the Rodrigues solitaire. In 1921, the American linguist Geoffroy Atkinson claimed Leguat's memoir was merely a novel, and that the man had never even existed, and in 1955, the British ecologist George Evelyn Hutchinson doubted aspects of the bird's biology mentioned by Leguat. Today, it is widely accepted that Leguat's memoirs are credible observations of the bird in life. For many years the dodo and the Rodrigues solitaire were placed in a
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
of their own, the Raphidae (formerly Dididae), because their exact relationships with other pigeons were unresolved. Each was also placed in a
monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...
family (Raphidae and Pezophapidae, respectively), as it was thought that they had evolved their similarities independently. Osteological and
DNA analysis Genetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, or ...
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.


Evolution

In 2002, American geneticist Beth Shapiro and colleagues analysed the DNA of the dodo and the Rodrigues solitaire for the first time. Comparison of
mitochondria A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is us ...
l cytochrome ''b'' and 12S
rRNA Ribosomal ribonucleic acid (rRNA) is a type of non-coding RNA which is the primary component of ribosomes, essential to all cells. rRNA is a ribozyme which carries out protein synthesis in ribosomes. Ribosomal RNA is transcribed from ribosomal ...
sequences In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is call ...
isolated from the
femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...
of a Rodrigues solitaire and the tarsal of a dodo confirmed their close relationship and their placement within the
Columbidae Columbidae is a bird Family (biology), family consisting of doves and pigeons. It is the only family in the Order (biology), order Columbiformes. These are stout-bodied birds with small heads, relatively short necks and slender bills that in ...
. The genetic evidence was interpreted as showing the Southeast Asian
Nicobar pigeon The Nicobar pigeon or Nicobar dove (''Caloenas nicobarica'', Car: ') is a bird found on small islands and in coastal regions from the Andaman and Nicobar Islands, India, east through the Indonesian Archipelago, to the Solomons and Palau. It is ...
(''Caloenas nicobarica'') to be their closest living relative, followed by the crowned pigeons (''Goura'') of
New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; , fossilized , also known as Papua or historically ) is the List of islands by area, world's second-largest island, with an area of . Located in Melanesia in the southwestern Pacific Ocean, the island is ...
, and the superficially dodo-like
tooth-billed pigeon The tooth-billed pigeon (''Didunculus strigirostris''), also known as the ''manumea'', is a large pigeon found only in Samoa. It is the only living species of genus '' Didunculus''. A related extinct species, the Tongan tooth-billed pigeon ('' ...
(''Didunculus strigirostris'') from
Samoa Samoa, officially the Independent State of Samoa and known until 1997 as Western Samoa, is an island country in Polynesia, part of Oceania, in the South Pacific Ocean. It consists of two main islands (Savai'i and Upolu), two smaller, inhabited ...
. This
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
consists of generally ground-dwelling island endemic pigeons. The following
cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
shows the closest relationships of the dodo and the Rodrigues solitaire within Columbidae, based on Shapiro et al., 2002:Supplementary information
/ref> 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. Based on behavioural and morphological evidence, Jolyon C. Parish proposed that the dodo and Rodrigues solitaire should be placed in the Gourinae subfamily along with the ''Goura'' pigeons and others, in agreement with the genetic evidence In 2014, DNA of the only known specimen of the recently extinct
spotted green pigeon The spotted green pigeon or Liverpool pigeon (''Caloenas maculata'') is a species of pigeon which is most likely extinct. It was first mentioned and described in 1783 by John Latham, who had seen two specimens of unknown provenance and a drawin ...
(''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. The 2002 study indicated that the ancestors of the Rodrigues solitaire and the dodo diverged around the
Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...
Neogene The Neogene ( ,) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period million years ago. It is the second period of th ...
boundary. The
Mascarene Islands The Mascarene Islands (, ) or Mascarenes or Mascarenhas Archipelago is a group of islands in the Indian Ocean east of Madagascar consisting of islands belonging to the Republic of Mauritius as well as the French department of Réunion. Their na ...
(Mauritius, Réunion, and Rodrigues), are of
volcanic A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often fo ...
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 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 Leapfrogging was an amphibious military strategy employed by the Allies in the Pacific War against the Empire of Japan during World War II. The key idea was to bypass heavily fortified enemy islands instead of trying to capture every island i ...
from South Asia. The lack of
mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
ian
herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...
s competing for resources on these islands allowed the solitaire and the dodo to attain very large sizes. 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 A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
material from
Fiji Fiji, officially the Republic of Fiji, is an island country in Melanesia, part of Oceania in the South Pacific Ocean. It lies about north-northeast of New Zealand. Fiji consists of an archipelago of more than 330 islands—of which about ...
. It was only slightly smaller than the Rodrigues solitaire and the dodo, and it too is thought to have been related to the crowned pigeons.


Description

The beak of the Rodrigues solitaire was slightly hooked, and its neck and legs were long. One observer described it as the size of a swan. The skull was long, flattened at the top with the fore and hind parts elevated into two bony ridges structured with
cancellous bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, an ...
. A black band (a contemporary description described it as a "frontlet") appeared on its head just behind the base of the beak. The
plumage Plumage () is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, there can b ...
of the Rodrigues solitaire was described as grey and brown. Females were paler than males and had elevations on the lower neck. Sexual size dimorphism in this species is perhaps the greatest in any
neognath Neognathae (; ) is an infraclass of birds, called neognaths, within the class Aves of the clade Archosauria. Neognathae includes the majority of living birds; the exceptions being the tinamous and the flightless ratites, which belong instead to ...
bird. Males were considerably larger than females, measuring in height and weighing up to , whereas females were and weighed . This is only 60% of the weight of a mature male. Their weight may have varied substantially due to fat cycles, meaning that individuals were fat during cool seasons, but slim during hot seasons, and may have been as low as 21 kg in males and 13 kg in females. Though male pigeons are usually larger than females, there is no direct evidence for the largest specimens actually being the males of the species, and this has only been assumed based on early works. Though the male was probably largest, this can only be confirmed by molecular sexing techniques, and not skeletal morphology alone. Members of both sexes possessed a large tuberous knob of bone
exostosis An exostosis, also known as a osteochondroma, is a benign chondrogenic lesions derived from aberrant cartilage from the perichondral ring. Exostoses can cause chronic pain ranging from mild to moderate, but rarely severe, depending on the shape, s ...
situated at the base of the
carpometacarpus The carpometacarpus is a bone found in the hands of birds. It results from the fusion of the carpal and metacarpal bone, and is essentially a single fused bone between the wrist and the knuckles. It is a smallish bone in most birds, generally fla ...
of each
wrist In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carpal ...
. Other wing bones also sometimes show similar structures. The knob was
cauliflower Cauliflower is one of several vegetables cultivated from the species '' Brassica oleracea'' in the genus '' Brassica'', which is in the Brassicaceae (or mustard) family. Cauliflower usually grows with one main stem that carries a large, rou ...
-like in appearance, and consisted of up to two or three lobes. The knobs were about half the length of the metacarpus, were larger in males than females, and described as the size of a
musket ball A musket is a muzzle-loaded long gun that appeared as a smoothbore weapon in the early 16th century, at first as a heavier variant of the arquebus, capable of penetrating plate armour. By the mid-16th century, this type of musket gradually d ...
. One study measured the largest knob to be in diameter. The knobs vary in size across individuals, and were entirely absent from 58% of specimens examined for the study. These are thought to be immature birds, or birds without territory. The carpometacarpi of males without the knobs were smaller on average than those with it, but there was little difference between the females. In life, the knobs would have been covered by tough
cartilaginous Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...
or
keratinous Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. It is the key structural material making up Scale (anatomy), scales, hair, Nail (anatomy), nails, feathers, horn (anatomy), horns, claws, Hoof, hoove ...
integument In biology, an integument is the tissue surrounding an organism's body or an organ within, such as skin, a husk, Exoskeleton, shell, germ or Peel (fruit), rind. Etymology The term is derived from ''integumentum'', which is Latin for "a coverin ...
, which would have made them appear even larger. Carpal spurs and knobs are also known from other extant as well as extinct birds. Within Columbidae, the crowned pigeons and the Viti Levu giant pigeon have outgrowths on the carpometacarpus which are similar to those of the female Rodrigues solitaire. Other well known examples are the steamer ducks, the torrent duck, sheathbills,
screamer The screamers are three South American bird species placed in Family (biology), family Anhimidae. They were thought to be related to the Galliformes because of similar beak, bills, but are more closely related to the family Anatidae, i.e. ducks ...
s, the
spur-winged goose The spur-winged goose (''Plectropterus gambensis'') is a large, Sub-Saharan African waterbird in the family Anatidae, which includes geese and shelducks. However, ''P. gambensis'' developed unique environmental adaptations, which resulted in t ...
, and the extinct Jamaican ibis, ''Xenicibis xympithecus''. The Rodrigues solitaire shared traits with the dodo, its closest relative, such as size and features in the skull,
pelvis The pelvis (: pelves or pelvises) is the lower part of an Anatomy, anatomical Trunk (anatomy), trunk, between the human abdomen, abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also c ...
, and
sternum The sternum (: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major bl ...
. It differed in other aspects; it was taller and more slender than the dodo and had a smaller skull and beak, a flatter
skull roof The skull roof or the roofing bones of the skull are a set of bones covering the brain, eyes and nostrils in bony fishes, including land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium. In com ...
, and larger
orbits In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an satellite, artificia ...
. Its neck and legs were proportionally longer, and the dodo did not possess an equivalent to the carpal knob of the Rodrigues solitaire. Many skeletal features of the Rodrigues solitaire and dodo that are unique among pigeons have evolved to adapt to flightlessness. Their pelvic elements were thicker than those of flighted birds (to support their greater weight), and their
pectoral Pectoral may refer to: * The chest region and anything relating to it. * Pectoral cross, a cross worn on the chest * a decorative, usually jeweled version of a gorget * Pectoral (Ancient Egypt), a type of jewelry worn in ancient Egypt * Pectora ...
region and wings were paedomorphic (underdeveloped, retaining juvenile features). However, the skull, trunk, and pelvic limbs were peramorphic, which means they changed considerably with maturity.


Contemporary descriptions

Apart from Leguat's rather simple depiction, the life appearance of the Rodrigues solitaire is only known from a handful of descriptions; no soft-tissue remains survive. Leguat devoted three pages of his memoirs to the Rodrigues solitaire, and was clearly impressed by the bird. He described its appearance as follows: Several of Leguat's observations were later confirmed through study of subfossil Rodrigues solitaire remains. The curved contour lines of the pelvis also support the roundness of its hind parts, which he compared to that of a horse. Also, a ridged surface appears at the base of the beak, indicating the position of the caruncular ridge, which Leguat described as a "
widow's peak A widow's peak is a V-shaped point in the hairline in the center of the forehead. Widow's Peak may also refer to: *'' Widows' Peak'', a 1994 British-Irish film *'' Widowspeak'', an American band ** ''Widowspeak'' (Widowspeak album), 2011 * ''Wido ...
". Before fossils of the carpal knob were found, Strickland noted that the keel of the sternum of the Rodrigues solitaire was so well-developed as to almost indicate it had possessed the power of flight; however, since the
humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...
was very short he inferred that this was instead related to Leguat's claim that they used their wings for defence. Leguat continued with an elaborate description of the female Rodrigues solitaire, which also appears to be the sex depicted in his illustration of the bird: It has been proposed that Leguat's comparison between the crop of the female Rodrigues solitaire and the "beautiful bosom of a woman" (changed to "fine neck" in some editions of his memoirs) was out of longing for female companionship. Leguat's statements were confirmed by another description by Julien Tafforet, who wrote in 1726:


Behaviour and ecology

Observations of the Rodrigues solitaire in life indicate that they were highly
territorial A territory is an area of land, sea, or space, belonging or connected to a particular country, person, or animal. In international politics, a territory is usually a geographic area which has not been granted the powers of self-government, ...
. They presumably settled disputes by striking each other with their wings; to aid this purpose, they used the knobs on their wrists. Fractures in their wing bones also indicate that they were used in combat. It has also been suggested that these fractures may have been the result of a hereditary bone disease rather than battle-injuries. But in all extant birds where carpal spurs and knobs are present, these are used as weapons without exceptions. Though some dodo bones have been found with healed fractures, it had weak pectoral muscles and more reduced wings in comparison with the Rodrigues solitaire. Since Rodrigues receives less rainfall and has more seasonal variation than Mauritius, which would have affected the availability of resources on the island, the Rodrigues solitaire would have more reason to evolve aggressive territorial behaviour. Several accounts state that they also defended themselves with a powerful bite. In addition to their use as weapons, both sexes of the Rodrigues solitaire also used their wings for communication. The wings could create low-frequency sounds for communicating with mates, or to warn rivals, but it is unknown exactly how this sound was created. The sound could be heard 200 yards (182 m) away, and this may therefore be the size of the territory of an individual. Other species of birds (e.g., club-winged manakin) are also known to use their wings to create sounds that attract mates or mark their territory. In 1869, the Newton brothers suggested that the carpal knobs may have been formed through continuous injuries, as they resemble diseased bone. It has also been claimed that the carpal knobs were instead formed due to a hereditary disease caused by inbreeding. This was dismissed in a 2013 study, since such lesions would likely not occur only in a specific part of the skeleton, but would appear in any growing bone tissue. If such a disease was due to inbreeding, it would also be present in other isolated island bird populations, but it is not. The authors instead suggested that the wing bones contained metaplastic tissue able to form the knob. This development was either in response to continuous impacts during combat, or to hormones released when individuals paired up and acquired territories. It appears a male which had long held a territory would possess especially large carpal knobs, and that their mates would have such developments as well, only smaller. Some evidence, including their large size and the fact that tropical and
frugivorous A frugivore ( ) is an animal that thrives mostly on raw fruits or succulent fruit-like produce of plants such as roots, shoots, nuts and seeds. Approximately 20% of mammalian herbivores eat fruit. Frugivores are highly dependent on the abundance ...
birds have slower growth rates, indicates that the Rodrigues solitaire may have had a protracted development period. Based on mass estimates, it has been suggested the male could reach the age of 28, and the female 17. The French economist Pierre-André d'Héguerty, writing about his time on the island around 1735, stated that a captive Rodrigues solitaire (which he described as having a melancholic appearance) would always walk in the same line until running out of space, and then return. The species may have lived primarily in the island's woodlands, rather than on the shores. Many other of the endemic species of Rodrigues became extinct after the arrival of humans, so the
ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
of the island is heavily damaged. Before humans arrived, forests covered the island entirely, but very little remains today due to deforestation. The Rodrigues solitaire lived alongside other recently extinct birds such as the Rodrigues rail, the Rodrigues parrot,
Newton's parakeet Newton's parakeet (''Psittacula exsul''), also known as the Rodrigues parakeet or Rodrigues ring-necked parakeet, is an extinction, extinct species of parrot that was Endemism in birds, endemic to the Mascarene island of Rodrigues in the wester ...
, the Rodrigues starling, the Rodrigues scops owl, the Rodrigues night heron, and the
Rodrigues pigeon The Rodrigues pigeon or Rodrigues dove (''Nesoenas rodericanus'') is an extinct species of pigeon formerly endemic to the Mascarene island of Rodrigues (island), Rodrigues. It is known from a subfossil sternum and some other bones, and the descri ...
. Extinct reptiles include the domed Rodrigues giant tortoise, the saddle-backed Rodrigues giant tortoise, and the
Rodrigues day gecko The Rodrigues day gecko (''Phelsuma edwardnewtoni''), also known commonly as the Rodrigues blue-dotted day gecko, is an extinct species of day gecko, a lizard in the family Gekkonidae. The species was endemic to the island of Rodrigues, where it ...
.


Diet

Leguat stated that the Rodrigues solitaire fed on dates, whereas Tafforet mentioned seeds and leaves. No other accounts mention diet. It has been suggested it ate latan palm fruits, for which it competed with the now extinct '' Cylindraspis'' tortoises. It is not known how the young were fed, but related pigeons provide
crop milk Crop milk is a secretion from the lining of the crop of parent birds in some species that is regurgitated to young birds. It is found among all pigeons and doves where it is also referred to as pigeon milk. Crop milk is also secreted from the c ...
. The risings on the crop of the female may have covered glands that produced the crop milk. If the theory is correct, the birds may have practiced a division of labour, where the female stayed and fed the young crop milk, while the male collected food in the crop and delivered it to the female. It has been suggested that the maximum size attained by the solitaire and the dodo was limited by the amount of crop milk they were able to produce for their young during early growth. Several contemporary accounts state that the Rodrigues solitaire used gizzard stones. Dodos also did this, which may imply a similar diet. Leguat described the stones in the following passage, mentioning that Rodrigues solitaires refused to feed in captivity: In 1877 three stones were found in a cavern on Rodrigues, each near a Rodrigues solitaire skeleton, and were inferred to be the gizzard stones mentioned by Leguat. One of the stones was examined and found to be
dolerite Diabase (), also called dolerite () or microgabbro, is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine-grain ...
: somewhat rough, hard and heavy, , but hardly flat on one side as described by Leguat. This could be due to its association with a young individual. Although Leguat asserted that the bird hatched with the gizzard stone already inside, in reality adults most likely fed the stones to their hatchlings.


Reproduction

The most detailed account of the reproductive habits of the Rodrigues solitaire is Leguat's. He described mating and nesting as follows: The
clutch A clutch is a mechanical device that allows an output shaft to be disconnected from a rotating input shaft. The clutch's input shaft is typically attached to a motor, while the clutch's output shaft is connected to the mechanism that does th ...
was described as consisting of a single egg; given the bird's large size, this led to proposals that the solitaire was
K-selected In ecology, selection theory relates to the natural selection, selection of combinations of Trait (biological), traits in an organism that trade off between quantity and quality of offspring. The focus on either an increased quantity of offsprin ...
, which means it produced a low number of
altricial Precocial species in birds and mammals are those in which the young are relatively mature and mobile from the moment of birth or hatching. They are normally nidifugous, meaning that they leave the nest shortly after birth or hatching. Altricial ...
offspring, which required extensive parental care until maturity. The gathering of unrelated juveniles suggests that they formed crèches, which may have followed foraging adults as part of the learning process. A study of subfossil remains found that the carpal knob only developed after the bird reached skeletal maturity. Tafforet's account confirms Leguat's description of reproductive behaviour, adding that Rodrigues solitaires would even attack humans approaching their chicks: The size difference between sexes has led to the suggestion that the Rodrigues solitaire was not monogamous as stated by Leguat, and that this deeply religious man attributed the trait to the bird for moral reasons. It has been proposed that it was instead
polygynous Polygyny () is a form of polygamy entailing the marriage of a man to several women. The term polygyny is from Neoclassical Greek πολυγυνία (); . Incidence Polygyny is more widespread in Africa than in any other continent. Some scholar ...
, and the wing-rattling behaviour described for males suggests lek-mating, where males gather for competitive mating display. However, size dimorphism does occur in some monogamous birds; most other pigeons are monogamous as well. A 2015 article proposed that males invited females into their territories as secondary mates, which would result in the resident female acting aggressively towards the newcomer. Similar behaviour is seen in species that practice resource-defence polygyny. The territories probably provided all the food the birds needed in addition to acting as breeding-areas, and there was probably intense competition for favourable territories. The fact that Rodrigues island shrank by 90% at the end of the
Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
may also have contributed to such competition over territories, and thereby furthered sexual dimorphism.


Relationship with humans

The Dutch viceadmiral Hans Hendricksz Bouwer was the first to list "dodos", most likely referring to the Rodrigues solitaire, as part of the fauna of Rodrigues in 1601. The English traveller Sir Thomas Herbert mentioned "dodos" on Rodrigues again in 1634, and they were also mentioned in 1700. The next account, which was the first referring to the bird as the "solitaire", was published in François Leguat's 1708 memoir, ''A New Voyage to the East Indies''. Leguat was the leader of a group of nine French
Huguenot The Huguenots ( , ; ) are a Religious denomination, religious group of French people, French Protestants who held to the Reformed (Calvinist) tradition of Protestantism. The term, which may be derived from the name of a Swiss political leader, ...
refugees, who were the first to colonise the island from 1691 to 1693, after they were marooned there by their captain. His description of the Rodrigues solitaire and its behaviour is the most detailed account of the bird in life, and he also described other species that are now extinct. Leguat's observations are considered some of the first cohesive accounts of animal behaviour in the wild. He later left for Mauritius, but was too late to observe dodos there. The Huguenots praised the Rodrigues solitaires for their flavour, especially that of the young, and used their gizzard stones as
knife sharpener Knife sharpening is the process of making a knife or similar tool sharp by grinding against a hard, rough surface, typically a stone, or a flexible surface with hard particles, such as sandpaper. Additionally, a leather razor strop, or st ...
s. D'Héguerty later claimed these were also useful in
medicine Medicine is the science and Praxis (process), practice of caring for patients, managing the Medical diagnosis, diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment, Palliative care, palliation of their injury or disease, ...
, and referred to them as
bezoar A bezoar stone ( ) is a mass often found trapped in the gastrointestinal system, though it can occur in other locations. A pseudobezoar is an indigestible object introduced intentionally into the digestive system. There are several varieties o ...
s. The second most detailed description of the bird was found in an anonymous document rediscovered in 1874 called ''Relation de l'Ile Rodrigue'', which has been attributed to Julien Tafforet, a mariner marooned on Rodrigues in 1726. His observations are considered credible, though it is known he had a copy of Leguat's memoirs with him during his stay. Many old accounts mention that Rodrigues solitaires were hunted by humans. The Danish zoologist
Japetus Steenstrup Johannes Japetus Smith Steenstrup FRS(For) HFRSE (8 March 1813 – 20 June 1897) was a Danish zoologist, biologist, and professor. Life Born in Vang, Thy on 8 March 1813, he held a lectorate in mineralogy in Sorø until 1845 when he became a ...
noted that some Rodrigues solitaire remains bore traces of having been broken by a human or perhaps another large predator, to extract
bone marrow Bone marrow is a semi-solid biological tissue, tissue found within the Spongy bone, spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It i ...
. Writing in 1735, the French lieutenant Gennes de la Chancelière described the capture and consumption of two specimens as follows: Unlike the dodo, no Rodrigues solitaires are known to have been sent to Europe alive. However, it has been claimed that the French naval officer
Bertrand-François Mahé de La Bourdonnais Bertrand-François Mahé, comte de La Bourdonnais (11 February 169910 November 1753) was a French Navy navy officer, officer and colonial administrator who was employed by the Louis XIV's East India Company, French East India Company. Biography ...
sent a "solitaire" to France from the nearby island of Réunion around 1740. Since the Réunion solitaire is believed to have become extinct by this date, the bird may actually have been a Rodrigues solitaire.


Extinction

The Rodrigues solitaire probably became
extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
sometime between the 1730s and 1760s; the exact date is unknown. Its disappearance coincided with the
tortoise Tortoises ( ) are reptiles of the family Testudinidae of the order Testudines (Latin for "tortoise"). Like other turtles, tortoises have a shell to protect from predation and other threats. The shell in tortoises is generally hard, and like o ...
trade between 1730 and 1750; traders burnt off vegetation, hunted solitaires and imported cats and pigs that preyed on eggs and chicks. In 1755, the French engineer Joseph-François Charpentier de Cossigny attempted to obtain a live specimen, as he had been assured the Rodrigues solitaire still survived in remote areas of the island. Though trying for 18 months, and offering large rewards, none could be found. He noted that cats were blamed for decimating the species, but suspected that it was due to hunting by humans instead. The French astronomer Alexandre Guy Pingré did not encounter any solitaires when he visited Rodrigues to observe the 1761 transit of Venus, although he had been assured they survived. His friend, the French astronomer
Pierre Charles Le Monnier Pierre Charles Le Monnier (; 20 November 1715 – 31 May 1799) was a French astronomer. His name is sometimes given as Lemonnier. Biography Le Monnier was born in Paris, where his father Pierre Lemonnier (physicist), Pierre (1675–1757), also ...
named the constellation
Turdus Solitarius Turdus Solitarius (Latin for ''solitary thrush'') was a constellation created by French astronomer Pierre Charles Le Monnier in 1776 from stars of Hydra's tail. It was named after the Rodrigues solitaire, an extinct flightless bird that was ende ...
after the bird to commemorate the journey. Although the Rodrigues solitaire is the only extinct bird to have a
former constellation Former constellations are old historical Western constellations that for various reasons are no longer widely recognised or are not officially recognised by the International Astronomical Union (IAU). Prior to 1930, many of these defunct const ...
named for it, celestial mapmakers did not know what it looked like and
star map A star chart is a celestial map of the night sky with astronomical objects laid out on a grid system. They are used to identify and locate constellations, stars, nebulae, galaxies, and planets. They have been used for human navigation since tim ...
s depicted other birds. By the time the discovery of subfossil Rodrigues solitaire bones from 1786 onwards confirmed Leguat's descriptions, no living residents of Rodrigues remembered having seen live specimens. In 1831, a man who had lived on Rodrigues for 40 years said that he had never seen birds large enough to be Rodrigues solitaires. Rodrigues covers only , making it implausible that the bird would have survived undetected.


References


External links

* * {{Featured article Extinct birds of Indian Ocean islands Extinct flightless birds Fauna of Rodrigues
Rodrigues solitaire The Rodrigues solitaire (''Pezophaps solitaria'') is an extinct flightless bird that was endemism, endemic to the island of Rodrigues, east of Madagascar in the Indian Ocean. Genetically within the family of Columbidae, pigeons and doves, it wa ...
Bird extinctions since 1500
Rodrigues solitaire The Rodrigues solitaire (''Pezophaps solitaria'') is an extinct flightless bird that was endemism, endemic to the island of Rodrigues, east of Madagascar in the Indian Ocean. Genetically within the family of Columbidae, pigeons and doves, it wa ...
Rodrigues solitaire The Rodrigues solitaire (''Pezophaps solitaria'') is an extinct flightless bird that was endemism, endemic to the island of Rodrigues, east of Madagascar in the Indian Ocean. Genetically within the family of Columbidae, pigeons and doves, it wa ...
A dagger, obelisk, or obelus is a typographical mark that usually indicates a footnote if an asterisk has already been used. The symbol is also used to indicate death (of people) or extinction (of species or languages). It is one of the mo ...