Monticolomys
Encyclopedia
Monticolomys is a genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of rodents within the subfamily Nesomyinae
Nesomyinae
The Malagasy rats and mice are the sole members of the subfamily Nesomyinae. These animals are the only native rodents of Madagascar, come in many shapes and sizes, and occupy a wide variety of ecological niches. There are nesomyines that resemble gerbils, rats, mice, voles, and even rabbits...

 of the family Nesomyidae
Nesomyidae
Nesomyidae is a family of African rodents in the large and complex superfamily Muroidea. It includes several subfamilies, all of which are native to either continental Africa or to Madagascar...

, and is closely related to Macrotarsomys
Macrotarsomys
Macrotarsomys is a genus of rodent in the family Nesomyidae.It contains the following species:Genus Macrotarsomys - Big-footed mice*Bastard Big-Footed Mouse, Macrotarsomys bastardi Milne-Edwards and G. Grandidier, 1898...

. The only species, Monticolomys koopmani, also known as the Malagasy Mountain Mouse or Koopman's Montane Voalavo, is found in the highlands of eastern Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...

. A small mouse-like rodent, M. koopmani is dark brown on the upperparts and dark gray below. It has small, rounded, densely haired ears and broad feet with well-developed pads. The long tail lacks a tuft at the tip. The skull is delicate and lacks crests and ridges on its roof.

First collected in 1929, Monticolomys koopmani was not formally described until 1996, but it is now known to have a broad distribution. Active during the night, it occurs in both montane forest
Cloud forest
A cloud forest, also called a fog forest, is a generally tropical or subtropical evergreen montane moist forest characterized by a persistent, frequent or seasonal low-level cloud cover, usually at the canopy level. Cloud forests often exhibit an abundance of mosses covering the ground and...

 and human-disturbed grasslands and feeds on fruits and seeds. A scansorial animal, it climbs trees but also lives on the ground. Although 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...

 may pose a threat, it is classified as "Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...

" on the IUCN Red List
IUCN 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...

.

Taxonomy

A specimen of Monticolomys koopmani was captured in 1929 during the Mission Zoologique Franco-Anglo-Américaine to Madagascar, but the rodents obtained by the expedition were never studied in detail. It was not until the 1970s that Karl Koopman
Karl Koopman
Karl Koopman was a zoologist with a special interest in bats. He worked for many years in the Mammalogy Department of the American Museum of Natural History in New York. Species named after him include Monticolomys koopmani, Rattus koopmani, and Sturnira koopmanhilli.-Further reading:...

 and 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...

 recognized that the animal—whose skin had landed at the American Museum of Natural History
American Museum of Natural History
The American Museum of Natural History , located on the Upper West Side of Manhattan in New York City, United States, is one of the largest and most celebrated museums in the world...

 in New York, while the skull was at the Muséum national d'histoire naturelle
Muséum national d'histoire naturelle
The Muséum national d'Histoire naturelle is the National Museum of Natural History in Paris, France.- History :The museum was formally founded on 10 June 1793, during the French Revolution...

 in Paris—represented an otherwise unknown species. However, they never published their results. In 1993, Steven Goodman
Steven Goodman
Steven Goodman is an American Conservation Biologist, and field biologist on staff in the Department of Zoology at the Field Museum of Natural History....

 rediscovered the species on Madagascar and in 1996 he and Michael Carleton finally published a formal description. They named the animal Monticolomys koopmani, as the sole member of a new genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

. The generic name Monticolomys means "mountain-dwelling mouse" and refers to the animal's montane habitat, and the specific name koopmani honors Karl Koopman for his many contributions to mammalian systematics. Common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...

s in use for the animal include "Koopman's Montane Voalavo" and "Malagasy Mountain Mouse".

The indigenous rodents of Madagascar, the Nesomyinae
Nesomyinae
The Malagasy rats and mice are the sole members of the subfamily Nesomyinae. These animals are the only native rodents of Madagascar, come in many shapes and sizes, and occupy a wide variety of ecological niches. There are nesomyines that resemble gerbils, rats, mice, voles, and even rabbits...

, prior to the discovery of Monticolomys comprised seven very distinctive genera—so distinct from each other that some have found it difficult to accept that they are closely related. Monticolomys, however, does not follow this pattern, in that it is similar and closely related to the gerbil
Gerbil
A gerbil is a small mammal of the order Rodentia. Once known simply as "desert rats", the gerbil subfamily includes about 110 species of African, Indian, and Asian rodents, including sand rats and jirds, all of which are adapted to arid habitats...

-like genus Macrotarsomys
Macrotarsomys
Macrotarsomys is a genus of rodent in the family Nesomyidae.It contains the following species:Genus Macrotarsomys - Big-footed mice*Bastard Big-Footed Mouse, Macrotarsomys bastardi Milne-Edwards and G. Grandidier, 1898...

of western Madagascar. This relationship was originally proposed by Goodman and Carleton based on morphology, and was strongly supported by a DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...

 analysis (based on the cytochrome b
Cytochrome b
Cytochrome b/b6 is the main subunit of transmembrane cytochrome bc1 and b6f complexes. In addition, it commonly refers to a region of mtDNA used for population genetics and phylogenetics.- Function :...

 gene) published in 1999. While this study provided some weak support for a relationship between the Macrotarsomys–Monticolomys clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 and the giant jumping rat, Hypogeomys, a later study based on the IRBP
RBP3
Retinol-binding protein 3, interstitial , also known as IRBP is a protein that in humans is encoded by the RBP3 gene. RBP3 orthologs have been identified in most eutherians except tenrecs and armadillos.- Function :...

 gene instead placed Macrotarsomys–Monticolomys sister to a clade containing four other nesomyine genera—Eliurus
Eliurus
Eliurus is a genus of rodent in the family Nesomyidae.It contains the following species:* Tsingy Tufted-tailed Rat * Ankarana Special Reserve Tufted-tailed Rat...

, Voalavo
Voalavo
Voalavo is a genus of rodent in the subfamily Nesomyinae, found only in Madagascar. Two species are known, both of which occur in mountain forest above 1250 m altitude; Voalavo gymnocaudus lives in northern Madagascar and Voalavo antsahabensis is restricted to a small area in the central part...

, Gymnuromys, and Brachytarsomys
Brachytarsomys
Brachytarsomys is a genus of rodent in the family Nesomyidae.It contains the following species:* White-tailed Antsangy * Brachytarsomys mahajambaensis * Hairy-tailed Antsangy...

.

Description

Monticolomys koopmani is a small, mouse-like rodent, and quite different in appearance from most other nesomyines. It has a thick, soft fur, which appears dark brown on the upperparts. The cover hairs (which comprise most of the fur) are tricolored: for the basal two thirds of their length, they are plumbeous gray; the middle is ochraceous; and the tip is dark brown to black. The longer guard hair
Guard hair
Guard hairs are the longest, coarsest hairs in a mammal's coat, forming the topcoat . They taper to a point and protect the undercoat from the elements. They are often water repellent and stick out above the rest of the coat...

s, which are most common towards the middle of the back, are completely black. The fur of the underparts appears dark gray, and is not sharply demarcated from the upperparts. There, the hairs are also plumbeous at the bases, but the tips range from white to yellowish-brown. The mystacial vibrissae—whiskers above the mouth—are medium-sized. The short, rounded ears are densely covered with grayish hairs. Monticolomys has broad hindfeet bearing prominent pads and long outer digits. There are white hairs on the upper sides of the metapodial
Metapodial
Metapodials are long bones of the hand and feet which connect the digits to the centers. In humans, five are present in each hand and foot....

s and digits, and long ungual tuft
Ungual tuft
In mammals, ungual tufts are tufts of hairs at the base of claws of the fore- and hindfeet. Their presence has been used as a character in cladistic studies of Cricetidae....

s—tufts of hair surrounding the bases of the claws—are present. The thumb of the forefeet bears a nail, but claws are present on the other digits. The long tail is covered with small scales and light brown hairs. The tail lacks a distinct tuft at the tip, as is present in Eliurus and Macrotarsomys. Females have six mammae. Head and body length is 84 to 101 mm (3.3 to 4 in), tail length is 116 to 143 mm (4.6 to 5.6 in), hindfoot length is 23 to 25 mm (0.9 to 1 in), ear length is 15 to 20 mm (0.6 to 0.8 in), and body mass is 18.5 to 27.5 g (0.7 to 1 oz).

The skull is small and delicate. The front part, the rostrum, is narrow and relatively long. 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 are rounded at the front, but blunt at the back. The zygomatic plate
Zygomatic plate
In rodent anatomy, the zygomatic plate is a bony plate derived from the flattened front part of the zygomatic arch . At the back, it connects to the front root of the zygomatic arch, and at the top it is connected to the rest of the skull via the antorbital bridge. It is part of the maxillary...

—a bony plate at the side of the skull—is narrow and extends back to the front margin of the first upper molar
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....

 (M1). The jugal bones constitute much of the thin 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). 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....

, between the eyes, is narrow and hourglass-shaped. There are no crests or ridges on the interorbital region or on the braincase. The incisive foramina, openings in 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...

, extend back to a point between the front roots of the M1s. The bony palate itself is broad and lacks many indentations and protuberances present in other species. Its posterior margin is at the level of the upper third molars (M3s). There is no alisphenoid strut
Alisphenoid strut
In some rodents, the alisphenoid strut is an extension of the alisphenoid bone that separates two foramina in the skull, the masticatory–buccinator foramen and the foramen ovale accessorius...

, so that the masticatory-buccinator foramen and the foramen ovale accessorius, two openings on the underside of the skull, are fused. There are 13 thoracic (chest), 7 lumbar (abdomen), 4 sacral (hip), and 38 caudal (tail) vertebrae.

The upper incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...

s have orange enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...

 and are opisthodont, with the cutting edge of the tooth inclined backwards. The root of the lower incisors extends though the mandible (lower jaw) to a low capsular process
Capsular process
In rodents, the capsular process or projection is a bony capsule that contains the root of the lower incisor. It is visible on the labial side of the mandible as a raising in the bone...

 at the back of the jawbone. The molars are brachyodont (low-crowned) and bear distinct cusps
Cusp (dentistry)
A cusp is an occlusal or incisal eminence on a tooth.Canine teeth, otherwise known as cuspids, each possess a single cusp, while premolars, otherwise known as bicuspids, possess two each. Molars normally possess either four or five cusps...

. The second molars, although decidedly smaller than the first, are similar in their crown morphology, but the much smaller third molars are reduced and more distinct from the first molars in morphology. The molars lack accessory crests and other features. Each of the upper molars is three-rooted, whereas the lowers have two roots. The molars are quite similar to those of Macrotarsomys, and differ only in minor details.

Distribution and ecology

The range of Monticolomys is now known to extend across the mountain ranges of eastern Madagascar from the Tsaratanana Massif south to Andohahela, at 800 to 2200 m (2600 to 7200 ft) above sea level. It occurs in montane forest, but also in degraded grassland, where it is among the first species to return after fires. At Ankaratra
Ankaratra
Ankaratra is an extinct/dormant volcano range located about 50 kilometers southwest of Antananarivo, the capital city of Madagascar. It lies between the towns of Arivonimamo to the North, Ambatolampy to the East, Faratsiho to the West and Betafo to the South...

, where the species was recorded in 1929, it occurred in such grassland, where the nesomyine Brachyuromys betsileoensis was also found. The animal was again recorded at Ankaratra in 1996, this time in a heavily disturbed forest, where it occurred with Eliurus minor and the introduced black rat
Black 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). At Andringitra
Andringitra Massif
The Andringitra Massif is a granite massif located within Andringitra National Park in Madagascar. Pic Boby, the highest peak, is at 2658 meters high. Today, it is mainly occupied by herders and shepherds who are constantly moving in order to find the freshest grazing grounds for their livestock...

, the animal was recorded in high montane forest together with six other nesomyines—Brachyuromys ramirohitra, Eliurus minor, Eliurus tanala, Eliurus webbi, Gymnuromys roberti, and Nesomys rufus—as well as the black rat. At Andohahela, Monticolomys was found at an altitude of 1875 m (6151.6 ft) in sclerophyllous forest. Its distribution corresponds to the High Mountain Domain, a region defined on the basis of plant distributions. This region is now discontinuous, but the High Mountain Domain habitat was continuous from mountain to mountain as recently as the early 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"...

. 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....

 remains of Monticolomys have been found in Mahajanga Province
Mahajanga Province
Mahajanga is a former province of Madagascar with an area of 150,023 km². It had a population of 1,896,000 . Its capital was Mahajanga.Except for Fianarantsoa, Mahajanga Province bordered all of the country's other provinces:...

 (northwestern Madagascar). Monticolomys koopmani is morphologically uniform across its wide distribution.

Monticolomys is nocturnal and solitary and produces litters of up to three offspring. It is scansorial, spending time on the ground but also climbing in vegetation. In Andringitra, two specimens were captured on a liana
Liana
A liana is any of various long-stemmed, woody vines that are rooted in the soil at ground level and use trees, as well as other means of vertical support, to climb up to the canopy to get access to well-lit areas of the forest. Lianas are especially characteristic of tropical moist deciduous...

 2 m (7 ft) over the ground, and a third was caught on the ground together with two shrew tenrecs (Microgale taiva). All five specimens from Andohahela were trapped on the ground, as was the specimen caught in Ankaratra in 1996. Its diet includes fruits and seeds; in captivity, it eats Agauria fruits.

Conservation status

As Monticolomys koopmani is now known to be a widespread, common species occurring in at least one protected area
Protected area
Protected areas are locations which receive protection because of their recognised natural, ecological and/or cultural values. There are several kinds of protected areas, which vary by level of protection depending on the enabling laws of each country or the regulations of the international...

 (Andringitra National Park
Andringitra National Park
Andringitra National Park is National Park in the Haute Matsiatra Region of Madagascar, 47 km south of Ambalavao. Approximately 140 km of the Tropic of Capricorn crosses the park....

; it may also occur in Ankarana Special Reserve), it is listed on the IUCN Red List
IUCN 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...

 as "Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...

". However, fires pose a threat in montane forest and, at lower elevations, its habitat is being converted into agricultural land.

Literature cited

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