Jamaican Rice Rat
Encyclopedia
Oryzomys antillarum, also known as the Jamaican rice rat, is an extinct
rodent
of Jamaica
. A member of the genus Oryzomys
within the family Cricetidae
, it is similar to O. couesi of mainland Central America, from where it may have dispersed to its island during the last glacial period. O. antillarum is common in subfossil
cave faunas and is also known from three specimens collected live in the 19th century. Some historical records of Jamaican rats may pertain to it. The species probably became extinct late in the 19th century, perhaps due to the introduction
of the small Asian mongoose, competition with introduced rodents such as the brown rat
, and habitat destruction
.
Oryzomys antillarum was a medium-sized rat, similar in most respects to Oryzomys couesi. The head and body length was 120 to 132 mm (4.7 to 5.2 in) and the skull was about 30 mm (1.2 in) long. The upperparts were reddish and graded into the yellowish underparts. The tail was about as long as the head and body, sparsely haired, and darker above than below. The species differed from O. couesi in having longer nasal bone
s, shorter incisive foramina
(perforations of the front part of the palate
), and more robust zygomatic arch
es (cheekbones).
on North American rodents, Elliott Coues
mentioned two specimens of Oryzomys from Jamaica in the collections of the United States National Museum (USNM). According to Coues, the specimens were similar to the marsh rice rat
(Oryzomys palustris) of the United States, but different in color. Although he wrote that they probably represented a separate form, he refrained from giving a scientific name to them because of the possibility that the form had already received a name he did not know of. The species was first formally described by Oldfield Thomas
in 1898 based on a specimen that had been in the British Museum of Natural History since 1845. He recognized it as a separate species of Oryzomys
, Oryzomys antillarum, but wrote that it was related to the mainland Central American O. couesi. Thomas suspected that the species was already extinct on Jamaica, but that it or a similar rice rat could still be found in the unexplored interior of Cuba
or Hispaniola
.
Revising North American Oryzomys in 1918, Edward Alphonso Goldman
retained O. antillarum as a separate species, but conceded that it was so similar to mainland O. couesi that it may have been introduced on Jamaica. In 1920, Harold Anthony reported that remains of O. antillarum were common in coastal caves, suggesting that the species had previously been an important part of the diet of the barn owl
(Tyto alba). In 1942, Glover Morrill Allen
doubted that it was even a distinct species and in his 1962 Ph.D. thesis, Clayton Ray, who examined numerous cave specimens, agreed and retained it as only a "weakly differentiated subspecies" of Oryzomys palustris (which by then included O. couesi and other Mexican and Central American forms), Oryzomys palustris antillarum. Philip Hershkovitz
came to the same conclusion in a 1966 paper. After O. couesi of Mexico and Central America was again classified as a species distinct from the marsh rice rat (O. palustris) of the United States, the Jamaican form came to be regarded as a subspecies of the former, Oryzomys couesi antillarum.
In a 1993 review, Gary Morgan reinstated the animal as a distinct species closely related to O. couesi, citing an unpublished paper by Humphrey, Setzer, and himself. Guy Musser
and Michael Carleton, writing for the 2005 third edition of Mammal Species of the World
, continued to classify the Jamaican form as part of O. couesi, but did not reference Morgan. However, in a 2006 review of the contents of Oryzomys, Marcelo Weksler and colleagues listed O. antillarum as a separate species, citing Morgan, and in a 2009 paper on western Mexican Oryzomys Carleton and Joaquín Arroyo-Cabrales did the same.
According to the classification by Carleton and Arroyo-Cabrales, Oryzomys antillarum is one of eight species in the genus Oryzomys, which occurs from the eastern United States (O. palustris) into northwestern South America (O. gorgasi
). O. antillarum is further part of the O. couesi section, which is centered around the widespread Central American O. couesi and also includes various other species with more limited and peripheral distributions. Many aspects of the systematics
of the O. couesi section remain unclear and it is likely that the current classification underestimates the true diversity of the group. Oryzomys previously included many other species, which were progressively removed in various studies culminating in the 2006 paper by Weksler and colleagues, which excluded more than forty species from the genus. All are classified in the tribe Oryzomyini
("rice rats"), a diverse assemblage of American rodents of over a hundred species, and on higher taxonomic levels in the subfamily Sigmodontinae
of family Cricetidae
, along with hundreds of other species of mainly small rodents.
The skull was generally similar to that of Oryzomys couesi, as were the teeth. It was robust and bore well-developed supraorbital ridge
s (located above the eyes) on the braincase. The interparietal bone, part of the roof of the braincase, was small and narrow. The bony palate
extended beyond the third molars. The nasal bone
s extended further back than the premaxillaries, whereas these bones are usually about coterminous in O. couesi. On average, the incisive foramina
, which perforate the front part of the palate, were shorter than in O. couesi. The zygomatic arch
(cheekbone) appears to have been better developed in O. antillarum.
In the three modern and numerous cave specimens, condylobasal length (a measure of skull length) varies from 28.9 to 31.2 mm (1.14 to 1.23 in) (one modern and two cave specimens only), length of the bony palate from 13.0 to 17.8 mm (0.51 to 0.70 in), width of the interorbital region
(located between the eyes) from 4.78 to 6.33 mm (0.188 to 0.249 in), length of the incisive foramina from 5.1 to 6.6 mm (0.20 to 0.26 in), crown length of the upper molars from 4.36 to 5.20 mm (0.172 to 0.205 in), and crown length of the lower molars from 4.80 to 5.39 mm (0.189 to 0.212 in).
system, where it was found in a stratum radiocarbon dated
to between 10,250 and 11,260 years before present
according to a 2002 study. It is present in several other undated sites that predate the human colonization of the island, around 1,400 years before present. However, a site (Wallingford Roadside Cave) from the last interglacial, the Eemian, contains only the hystricognath rodents Clidomys and Geocapromys browni and lacks Oryzomys. The presence of the rice rat on Jamaica before the arrival of humans disproves the hypothesis that it was introduced; instead, it must have reached the island by overwater dispersal
through a rafting event
, probably less than 125,000 years ago. During the last glacial period, low sea levels would have exposed much land between Jamaica and Central America, substantially decreasing the distance needed for the ancestor of O. antillarum to arrive on the island and probably influencing sea currents so that rafts of vegetation from Central America would be more likely to reach Jamaica. Species of Oryzomys are semiaquatic and closely associated with water, which may help to explain the occurrence of the genus on Jamaica. The rice rat has been found in many superficial, late Holocene
cave deposits, some of which have been radiocarbon dated to within the last 1,100 years. Its remains also occur in some Amerindian archeological sites. From its common and widespread occurrence in caves, Ray suggested that the rice rat occurred in many different habitats before European contact. O. antillarum was the only sigmodontine
rodent on any of the Greater Antilles
, where the rodent fauna otherwise consists solely of hystricognaths and introduced rodents.
, Rattus rattus; brown rat
, Rattus norvegicus; and house mouse
, Mus musculus). Patrick Browne
, in the 1756 Civil and Natural History of Jamaica, described a "House and Cane-Rat", a "Mouse", and a large "Water-Rat", which he said had been introduced to the island and become very common there.
In his History of Jamaica (1774), Edward Long
recognized four Jamaican rats: Browne's "Water-Rat", termed the "Charles-price rat", which Long regarded as identical with the European water vole
(Arvicola); the "black house-rat", said to have been brought from England; and two he said were indigenous. The larger of those was a grayish "cane-rat" and the smaller was a reddish "field-rat" as large as the English mole (the European mole
, Talpa europaea). Ray considered that the last may simply have been the house mouse, since the size of an English mole would be too small for Oryzomys.
In A Naturalist's Sojourn in Jamaica (1851), Philip Henry Gosse
listed the black and brown rat and the house mouse, as well as the "Cane-piece Rat", which he described as Mus saccharivorus and regarded as probably identical with Browne's "Water-Rat" and Long's "Charles-price Rat". He also mentioned the two species Long had listed as indigenous. Thomas and Ray both asserted that this "Cane-piece Rat" was most likely a brown rat, as judged from its measurements. Gosse wrote that an early explorer, Anthony Robinson, had described and pictured this species in an unpublished manuscript, on the basis of a specimen 20 in (50 cm) long, half of which consisted of the tail. Ray was unable to examine Robinson's manuscript, but suggested that Robinson's rat could not have been the brown rat, because that species did not reach the Americas until about 1800, and may instead have been O. antillarum.
Gosse had collected the British Museum specimen of Oryzomys antillarum in 1845, but may not have separated it from introduced rats found with it. Coues noted that the two USNM specimens he examined were received after he had written the preceding part of his monograph; later, Thomas and others wrote that these specimens were obtained around 1877, but Ray asserted that they were taken before 1874. No specimens have been collected since.
. Its disappearance is usually attributed to the small Asian mongoose (Herpestes javanicus), which was introduced to Jamaica in 1872, and sometimes also to introduced Rattus species. Ray, on the other hand, argued that the significance of the mongoose had been overrated. Instead, he suggested that Oryzomys antillarum may have been affected by the massive environmental changes that occurred on the island after the British takeover in 1655. In that period, the bulk of the island came to be used for cultivation, so that the native habitat of Oryzomys was destroyed. Thus, Oryzomys was reduced to competition with introduced rats in man-made habitats, to which the latter are well adapted. Perhaps, Ray wrote, the black rat may not have been able to extirpate Oryzomys, but the brown rat, a later and more assertive invader, brought it to extinction. Cats and dogs preying on Oryzomys may also have contributed to its demise.
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
of Jamaica
Jamaica
Jamaica is an island nation of the Greater Antilles, in length, up to in width and 10,990 square kilometres in area. It is situated in the Caribbean Sea, about south of Cuba, and west of Hispaniola, the island harbouring the nation-states Haiti and the Dominican Republic...
. A member of the genus Oryzomys
Oryzomys
Oryzomys is a genus of semiaquatic rodents in the tribe Oryzomyini living in southern North America and far northern South America. It includes eight species, two of which—the marsh rice rat of the United States and O. couesi of Mexico and Central America—are widespread; the six others have...
within the family Cricetidae
Cricetidae
The Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, and New World rats and mice...
, it is similar to O. couesi of mainland Central America, from where it may have dispersed to its island during the last glacial period. O. antillarum is common in subfossil
Subfossil
Subfossil refers to remains whose fossilization process is not complete, either for lack of time or because the conditions in which they were buried were not optimal for fossilization....
cave faunas and is also known from three specimens collected live in the 19th century. Some historical records of Jamaican rats may pertain to it. The species probably became extinct late in the 19th century, perhaps due to the introduction
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
of the small Asian mongoose, competition with introduced rodents such as the brown rat
Brown Rat
The brown rat, common rat, sewer rat, Hanover rat, Norway rat, Brown Norway rat, Norwegian rat, or wharf rat is one of the best known and most common rats....
, and habitat destruction
Habitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...
.
Oryzomys antillarum was a medium-sized rat, similar in most respects to Oryzomys couesi. The head and body length was 120 to 132 mm (4.7 to 5.2 in) and the skull was about 30 mm (1.2 in) long. The upperparts were reddish and graded into the yellowish underparts. The tail was about as long as the head and body, sparsely haired, and darker above than below. The species differed from O. couesi in having longer nasal bone
Nasal bone
The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, and form, by their junction, "the bridge" of the nose.Each has two surfaces and four borders....
s, shorter incisive foramina
Incisive foramen
The fossa incisiva is an opening in the bone of the oral hard palate where blood vessels and nerves may pass. There are four of these openings in the incisive fossa.-Formation:...
(perforations of the front part of the palate
Palate
The palate is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but, in most other tetrapods, the oral and nasal cavities are not truly separate. The palate is divided into two parts, the anterior...
), and more robust zygomatic arch
Zygomatic arch
The zygomatic arch or cheek bone is formed by the zygomatic process of temporal bone and the temporal process of the zygomatic bone , the two being united by an oblique suture; the tendon of the Temporalis passes medial to the arch to gain insertion into the coronoid process...
es (cheekbones).
Taxonomy
In his 1877 monographMonograph
A monograph is a work of writing upon a single subject, usually by a single author.It is often a scholarly essay or learned treatise, and may be released in the manner of a book or journal article. It is by definition a single document that forms a complete text in itself...
on North American rodents, Elliott Coues
Elliott Coues
Elliott Coues was an American army surgeon, historian, ornithologist and author.Coues was born in Portsmouth, New Hampshire. He graduated at Columbian University, Washington, D.C., in 1861, and at the Medical school of that institution in 1863...
mentioned two specimens of Oryzomys from Jamaica in the collections of the United States National Museum (USNM). According to Coues, the specimens were similar to the marsh rice rat
Marsh Rice Rat
The marsh rice rat is a semiaquatic North American rodent in the family Cricetidae. It is found mostly in the eastern and southern United States, from New Jersey and Kansas south to Florida and northeasternmost Tamaulipas, Mexico; its range previously extended further west and north, where it may...
(Oryzomys palustris) of the United States, but different in color. Although he wrote that they probably represented a separate form, he refrained from giving a scientific name to them because of the possibility that the form had already received a name he did not know of. The species was first formally described by Oldfield Thomas
Oldfield Thomas
Oldfield Thomas FRS was a British zoologist.Thomas worked at the Natural History Museum on mammals, describing about 2,000 new species and sub-species for the first time. He was appointed to the Museum Secretary's office in 1876, transferring to the Zoological Department in 1878...
in 1898 based on a specimen that had been in the British Museum of Natural History since 1845. He recognized it as a separate species of Oryzomys
Oryzomys
Oryzomys is a genus of semiaquatic rodents in the tribe Oryzomyini living in southern North America and far northern South America. It includes eight species, two of which—the marsh rice rat of the United States and O. couesi of Mexico and Central America—are widespread; the six others have...
, Oryzomys antillarum, but wrote that it was related to the mainland Central American O. couesi. Thomas suspected that the species was already extinct on Jamaica, but that it or a similar rice rat could still be found in the unexplored interior of Cuba
Cuba
The Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...
or Hispaniola
Hispaniola
Hispaniola is a major island in the Caribbean, containing the two sovereign states of the Dominican Republic and Haiti. The island is located between the islands of Cuba to the west and Puerto Rico to the east, within the hurricane belt...
.
Revising North American Oryzomys in 1918, Edward Alphonso Goldman
Edward Alphonso Goldman
Edward Alphonso Goldman was an American zoologist. He worked extensively in Mexico with Edward William Nelson and described and revised many groups of mammals....
retained O. antillarum as a separate species, but conceded that it was so similar to mainland O. couesi that it may have been introduced on Jamaica. In 1920, Harold Anthony reported that remains of O. antillarum were common in coastal caves, suggesting that the species had previously been an important part of the diet of the barn owl
Barn Owl
The Barn Owl is the most widely distributed species of owl, and one of the most widespread of all birds. It is also referred to as Common Barn Owl, to distinguish it from other species in the barn-owl family Tytonidae. These form one of two main lineages of living owls, the other being the typical...
(Tyto alba). In 1942, Glover Morrill Allen
Glover Morrill Allen
Glover Morrill Allen was an American zoologist.He was born at Walpole, New Hampshire, the son of Reverend Nathaniel Glover Allen and Harriet Ann Allen, and studied at Harvard University,...
doubted that it was even a distinct species and in his 1962 Ph.D. thesis, Clayton Ray, who examined numerous cave specimens, agreed and retained it as only a "weakly differentiated subspecies" of Oryzomys palustris (which by then included O. couesi and other Mexican and Central American forms), Oryzomys palustris antillarum. Philip Hershkovitz
Philip Hershkovitz
Philip Hershkovitz was an American mammalogist. Born in Pittsburgh, he attended the Universities of Pittsburgh and Michigan and lived in South America collecting mammals. In 1947, he was appointed a curator at the Field Museum of Natural History in Chicago and he continued to work there until his...
came to the same conclusion in a 1966 paper. After O. couesi of Mexico and Central America was again classified as a species distinct from the marsh rice rat (O. palustris) of the United States, the Jamaican form came to be regarded as a subspecies of the former, Oryzomys couesi antillarum.
In a 1993 review, Gary Morgan reinstated the animal as a distinct species closely related to O. couesi, citing an unpublished paper by Humphrey, Setzer, and himself. Guy Musser
Guy Musser
Guy Graham Musser is an American zoologist. His main research field is the subfamily Murinae, in which he has described many new species.Musser was born in Salt Lake City, Utah...
and Michael Carleton, writing for the 2005 third edition of Mammal Species of the World
Mammal Species of the World
Mammal Species of the World, now in its 3rd edition, is a standard reference work in zoology giving descriptions and bibliographic data for the known species of mammals.An updated Third Edition of Mammal Species of the World was published late in 2005:...
, continued to classify the Jamaican form as part of O. couesi, but did not reference Morgan. However, in a 2006 review of the contents of Oryzomys, Marcelo Weksler and colleagues listed O. antillarum as a separate species, citing Morgan, and in a 2009 paper on western Mexican Oryzomys Carleton and Joaquín Arroyo-Cabrales did the same.
According to the classification by Carleton and Arroyo-Cabrales, Oryzomys antillarum is one of eight species in the genus Oryzomys, which occurs from the eastern United States (O. palustris) into northwestern South America (O. gorgasi
Oryzomys gorgasi
Oryzomys gorgasi, also known as Gorgas's Oryzomys or Gorgas's Rice Rat, is a rodent in the genus Oryzomys of family Cricetidae. First collected as a living animal in 1967, it is known from only a few localities, including a freshwater swamp in the lowlands of northwestern Colombia and a mangrove...
). O. antillarum is further part of the O. couesi section, which is centered around the widespread Central American O. couesi and also includes various other species with more limited and peripheral distributions. Many aspects of the systematics
Systematics
Biological systematics is the study of the diversification of terrestrial life, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees...
of the O. couesi section remain unclear and it is likely that the current classification underestimates the true diversity of the group. Oryzomys previously included many other species, which were progressively removed in various studies culminating in the 2006 paper by Weksler and colleagues, which excluded more than forty species from the genus. All are classified in the tribe Oryzomyini
Oryzomyini
Oryzomyini is a tribe of rodents in the subfamily Sigmodontinae of family Cricetidae. It includes about 120 species in about thirty genera, distributed from the eastern United States to the southernmost parts of South America, including many offshore islands...
("rice rats"), a diverse assemblage of American rodents of over a hundred species, and on higher taxonomic levels in the subfamily Sigmodontinae
Sigmodontinae
The subfamily Sigmodontinae is one of the most diverse groups of mammals. It includes New World rats and mice, with at least 376 species. Many authorities include the Neotominae and Tylomyinae as part of a larger definition of Sigmodontinae. When those genera are included, the species count...
of family Cricetidae
Cricetidae
The Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, and New World rats and mice...
, along with hundreds of other species of mainly small rodents.
Description
Oryzomys antillarum was a medium-sized rodent, about as large as O. couesi. According to Thomas's description, the upperparts were reddish, slightly brighter on the rump and more grayish on the head. The color of the upperparts graded into that of the underparts, which were yellowish. The hairs of the underparts were grayish at the bases. The small ears were black on the outer and yellow on the inner side and the upper surfaces of the hands and feet were whitish. The tail was nearly naked and was light brownish above and lighter below. Goldman wrote that the specimens in the USNM were rather more reddish, but their color may have been altered because they had been preserved in alcohol. Coues had described these as rusty brown above and washed with the same color below. Andrew Arata compared the USNM specimens with examples of the reddish Florida subspecies of the marsh rice rat, Oryzomys palustris natator, for Ray and found that they were more reddish than even the most strongly colored animals from Florida.The skull was generally similar to that of Oryzomys couesi, as were the teeth. It was robust and bore well-developed supraorbital ridge
Supraorbital ridge
The supraorbital ridge, or brow ridge, refer to a bony ridge located above the eye sockets of all primates. In Homo sapiens sapiens the eyebrows are located on their lower margin.Other terms in use are:* supraorbital arch...
s (located above the eyes) on the braincase. The interparietal bone, part of the roof of the braincase, was small and narrow. The bony palate
Palate
The palate is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but, in most other tetrapods, the oral and nasal cavities are not truly separate. The palate is divided into two parts, the anterior...
extended beyond the third molars. The nasal bone
Nasal bone
The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, and form, by their junction, "the bridge" of the nose.Each has two surfaces and four borders....
s extended further back than the premaxillaries, whereas these bones are usually about coterminous in O. couesi. On average, the incisive foramina
Incisive foramen
The fossa incisiva is an opening in the bone of the oral hard palate where blood vessels and nerves may pass. There are four of these openings in the incisive fossa.-Formation:...
, which perforate the front part of the palate, were shorter than in O. couesi. The zygomatic arch
Zygomatic arch
The zygomatic arch or cheek bone is formed by the zygomatic process of temporal bone and the temporal process of the zygomatic bone , the two being united by an oblique suture; the tendon of the Temporalis passes medial to the arch to gain insertion into the coronoid process...
(cheekbone) appears to have been better developed in O. antillarum.
In the three modern and numerous cave specimens, condylobasal length (a measure of skull length) varies from 28.9 to 31.2 mm (1.14 to 1.23 in) (one modern and two cave specimens only), length of the bony palate from 13.0 to 17.8 mm (0.51 to 0.70 in), width of the interorbital region
Interorbital region
The interorbital region of the skull is located between the eyes, anterior to the braincase. The form of the interorbital region may exhibit significant variation between taxonomic groups....
(located between the eyes) from 4.78 to 6.33 mm (0.188 to 0.249 in), length of the incisive foramina from 5.1 to 6.6 mm (0.20 to 0.26 in), crown length of the upper molars from 4.36 to 5.20 mm (0.172 to 0.205 in), and crown length of the lower molars from 4.80 to 5.39 mm (0.189 to 0.212 in).
Origin and subfossil records
The oldest well-dated record of Oryzomys antillarum is at Drum Cave in the Jacksons Bay CavesJackson's Bay Cave
Jackson's Bay Cave is a very large cave system on the Portland Ridge in Clarendon near the south coast of Jamaica. It is considered to be one of the most beautiful in the Caribbean...
system, where it was found in a stratum radiocarbon dated
Radiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
to between 10,250 and 11,260 years before present
Before Present
Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...
according to a 2002 study. It is present in several other undated sites that predate the human colonization of the island, around 1,400 years before present. However, a site (Wallingford Roadside Cave) from the last interglacial, the Eemian, contains only the hystricognath rodents Clidomys and Geocapromys browni and lacks Oryzomys. The presence of the rice rat on Jamaica before the arrival of humans disproves the hypothesis that it was introduced; instead, it must have reached the island by overwater dispersal
Biological dispersal
Biological dispersal refers to species movement away from an existing population or away from the parent organism. Through simply moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but also for population dynamics, population...
through a rafting event
Rafting event
Oceanic dispersal is a type of biological dispersal that occurs when organisms transfer from one land mass to another by way of a sea crossing on large clumps of floating vegetation. Such matted clumps of vegetation are often seen floating down major rivers in the tropics and washing out to sea,...
, probably less than 125,000 years ago. During the last glacial period, low sea levels would have exposed much land between Jamaica and Central America, substantially decreasing the distance needed for the ancestor of O. antillarum to arrive on the island and probably influencing sea currents so that rafts of vegetation from Central America would be more likely to reach Jamaica. Species of Oryzomys are semiaquatic and closely associated with water, which may help to explain the occurrence of the genus on Jamaica. The rice rat has been found in many superficial, late Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
cave deposits, some of which have been radiocarbon dated to within the last 1,100 years. Its remains also occur in some Amerindian archeological sites. From its common and widespread occurrence in caves, Ray suggested that the rice rat occurred in many different habitats before European contact. O. antillarum was the only sigmodontine
Sigmodontinae
The subfamily Sigmodontinae is one of the most diverse groups of mammals. It includes New World rats and mice, with at least 376 species. Many authorities include the Neotominae and Tylomyinae as part of a larger definition of Sigmodontinae. When those genera are included, the species count...
rodent on any of the Greater Antilles
Greater Antilles
The Greater Antilles are one of three island groups in the Caribbean. Comprising Cuba, Jamaica, Hispaniola , and Puerto Rico, the Greater Antilles constitute almost 90% of the land mass of the entire West Indies.-Greater Antilles in context :The islands of the Caribbean Sea, collectively known as...
, where the rodent fauna otherwise consists solely of hystricognaths and introduced rodents.
Historical records
Although there are some early historical records of the rats of Jamaica, very little is to be found in them regarding Oryzomys antillarum, perhaps because the species declined rapidly following the European colonization of the island and because early authors failed to distinguish it from introduced rodents (the black ratBlack Rat
The black rat is a common long-tailed rodent of the genus Rattus in the subfamily Murinae . The species originated in tropical Asia and spread through the Near East in Roman times before reaching Europe by the 1st century and spreading with Europeans across the world.-Taxonomy:The black rat was...
, Rattus rattus; brown rat
Brown Rat
The brown rat, common rat, sewer rat, Hanover rat, Norway rat, Brown Norway rat, Norwegian rat, or wharf rat is one of the best known and most common rats....
, Rattus norvegicus; and house mouse
House mouse
The house mouse is a small rodent, a mouse, one of the most numerous species of the genus Mus.As a wild animal the house mouse mainly lives associated with humans, causing damage to crops and stored food....
, Mus musculus). Patrick Browne
Patrick Browne
Patrick Browne was an Irish physician and botanist.-Career:Browne was born in Woodstock, County Mayo, sent to relatives on Antigua in 1737 and returned to Europe due to ill health after two years. He studied medicine, natural history and especially botany at Reims, Paris and Leyden, qualifying...
, in the 1756 Civil and Natural History of Jamaica, described a "House and Cane-Rat", a "Mouse", and a large "Water-Rat", which he said had been introduced to the island and become very common there.
In his History of Jamaica (1774), Edward Long
Edward Long
Edward Long was a British colonial administrator and historian, and author of an influential work, The History of Jamaica .-Life:...
recognized four Jamaican rats: Browne's "Water-Rat", termed the "Charles-price rat", which Long regarded as identical with the European water vole
Arvicola
The water voles are large voles in the genus Arvicola. They are found in both aquatic and dry habitat through Europe and much of northern Asia...
(Arvicola); the "black house-rat", said to have been brought from England; and two he said were indigenous. The larger of those was a grayish "cane-rat" and the smaller was a reddish "field-rat" as large as the English mole (the European mole
European Mole
The European Mole, Talpa europaea, is a mammal of the order Soricomorpha. It is also known as the Common Mole and the Northern Mole....
, Talpa europaea). Ray considered that the last may simply have been the house mouse, since the size of an English mole would be too small for Oryzomys.
In A Naturalist's Sojourn in Jamaica (1851), Philip Henry Gosse
Philip Henry Gosse
Philip Henry Gosse was an English naturalist and popularizer of natural science, virtually the inventor of the seawater aquarium, and a painstaking innovator in the study of marine biology...
listed the black and brown rat and the house mouse, as well as the "Cane-piece Rat", which he described as Mus saccharivorus and regarded as probably identical with Browne's "Water-Rat" and Long's "Charles-price Rat". He also mentioned the two species Long had listed as indigenous. Thomas and Ray both asserted that this "Cane-piece Rat" was most likely a brown rat, as judged from its measurements. Gosse wrote that an early explorer, Anthony Robinson, had described and pictured this species in an unpublished manuscript, on the basis of a specimen 20 in (50 cm) long, half of which consisted of the tail. Ray was unable to examine Robinson's manuscript, but suggested that Robinson's rat could not have been the brown rat, because that species did not reach the Americas until about 1800, and may instead have been O. antillarum.
Gosse had collected the British Museum specimen of Oryzomys antillarum in 1845, but may not have separated it from introduced rats found with it. Coues noted that the two USNM specimens he examined were received after he had written the preceding part of his monograph; later, Thomas and others wrote that these specimens were obtained around 1877, but Ray asserted that they were taken before 1874. No specimens have been collected since.
Extinction
Oryzomys antillarum probably became extinct about the 1870s and is currently listed as such by the IUCN Red ListIUCN Red List
The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...
. Its disappearance is usually attributed to the small Asian mongoose (Herpestes javanicus), which was introduced to Jamaica in 1872, and sometimes also to introduced Rattus species. Ray, on the other hand, argued that the significance of the mongoose had been overrated. Instead, he suggested that Oryzomys antillarum may have been affected by the massive environmental changes that occurred on the island after the British takeover in 1655. In that period, the bulk of the island came to be used for cultivation, so that the native habitat of Oryzomys was destroyed. Thus, Oryzomys was reduced to competition with introduced rats in man-made habitats, to which the latter are well adapted. Perhaps, Ray wrote, the black rat may not have been able to extirpate Oryzomys, but the brown rat, a later and more assertive invader, brought it to extinction. Cats and dogs preying on Oryzomys may also have contributed to its demise.
Literature cited
- Allen, G.M. 1942. Extinct and vanishing mammals of the Western Hemisphere with the marine species of all the oceans. American Committee for International Wildlife Protection, Special Publications 11:1–620.
- Anthony, H.E. 1920. A zoologist in Jamaica. Natural History 20:157–168.
- Browne, P. 1756. The Civil and Natural History of Jamaica. In Three Parts. London, viii + 503 pp.
- Carleton, M.D. and Arroyo-Cabrales, J. 2009. Review of the Oryzomys couesi complex (Rodentia: Cricetidae: Sigmodontinae) in western Mexico. Bulletin of the American Museum of Natural History 331:94–127.
- Coues, E. 1877. Muridae. Pp. x+264 in Coues, E. and Allen, J.A. Monographs of North American Rodentia. Report of the United States Geological Survey of the Territories 11:xii+x+1091 pp.
- Fincham, A., Draper, G. and MacPhee, R. 2000. Jamaica Underground: The Caves, Sinkholes and Underground Rivers of the Island. 2nd ed. University of the West Indies Press, 447 pp. ISBN 978-976-640-036-1
- Goldman, E.A. 1918. The rice rats of North America. North American Fauna 43:1–100.
- Gosse, P.H. 1851. A naturalist's sojourn in Jamaica. London: Longman, Brown, Green, and Longmans, xxiv + 508 pp.
- Hershkovitz, P. 1966. Mice, land bridges, and Latin American faunal interchange. Pp. 725–795 in Wenzel, R.L. and Tipton, V.J. (eds.). Ectoparasites of Panama. Chicago: Field Museum of Natural History.
- Honacki, J.H., Kinman, K.E. and Koeppl, J.W. (eds.). 1982. Mammal Species of the World: A Taxonomic and Geographic Reference. 1st ed. Lawrence, Kansas: Allen Press, Inc., and The Association of Systematics Collections, 694 pp. ISBN 978-0-942924-00-8
- Long, E. 1774. The History of Jamaica. Volume 3. London: printed for T. Lowndes, pp. i–viii + 596–976.
- McFarlane, D.A., Lundberg, J. and Fincham, A.G. 2002. A late Quaternary paleoecological record from caves of southern Jamaica, West Indies. Journal of Cave and Karst Studies 64(2):117–125.
- Morgan, G.S. 1993. Quaternary land vertebrates of Jamaica. Geological Society of America Memoir 182:417–442.
- Musser, G.G. and Carleton, M.D. 2005. Superfamily Muroidea. Pp. 894–1531 in Wilson, D.E. and Reeder, D.M. (eds.). Mammal Species of the World: a taxonomic and geographic reference. 3rd ed. Baltimore: The Johns Hopkins University Press, 2 vols., 2142 pp. ISBN 978-0-8018-8221-0
- Ray, C.E. 1962. The Oryzomyine Rodents of the Antillean Subregion. Doctor of Philosophy thesis, Harvard University, 211 pp.
- Thomas, O. 1898. On indigenous Muridæ in the West Indies; with the description of a new Mexican Oryzomys. Annals and Magazine of Natural History (7)1:176–180.
- Turvey, S. and Helgen, K. 2008. . In IUCN. IUCN Red List of Threatened Species. Version 2009.2. <www.iucnredlist.org>. Downloaded on November 30, 2009.
- Weksler, M., Percequillo, A.R. and Voss, R.S. 2006. Ten new genera of oryzomyine rodents (Cricetidae: Sigmodontinae). American Museum Novitates 3537:1–29.