Koopman's Montane Voalavo

The Malagasy mountain mouse or Koopman's montane voalavo (''Monticolomys koopmani'') is a rodent within the subfamily Nesomyinae of the family Nesomyidae. It is monotypic within the genus ''Monticolomys'', and is closely related to the big-footed mouse ''(Macrotarsomys)''. It is found in the highlands of eastern Madagascar. A small mouse-like rodent, it 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, the Malagasy mountain mouse 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 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 may pose a threat, it is classified as "Least Concern" on the IUCN Red List.

Taxonomy

A specimen 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 and Guy Musser recognized that the animal—whose skin had landed at the American Museum of Natural History in New York, while the skull was at the Muséum national d'histoire naturelle in Paris—represented an otherwise unknown species. However, they never published their results. In 1993, Steven Goodman rediscovered the species on Madagascar and in 1996 he and Michael Carleton finally published a formal description.Carleton and Goodman, 1996, p. 232 They named the animal ''Monticolomys koopmani'', as the sole member of a new genus.Carleton and Goodman, 1996, p. 233 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.Carleton and Goodman, 1996, p. 242 Common names in use for the animal also include "Koopman's montane voalavo"Musser and Carleton, 2005, p. 952 and "Malagasy mountain mouse".

The indigenous rodents of Madagascar, the Nesomyinae, 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.Carleton and Goodman, 1996, p. 249 ''Monticolomys'', however, does not follow this pattern, in that it is similar and closely related to the gerbil-like genus '' Macrotarsomys'' of western Madagascar. This relationship was originally proposed by Goodman and Carleton based on morphology,Carleton and Goodman, 1996, p. 250 and was strongly supported by a DNA sequence analysis (based on the cytochrome ''b'' gene) published in 1999. While this study provided some weak support for a relationship between the ''Macrotarsomys–Monticolomys'' clade and the giant jumping rat, ''Hypogeomys'',Jansa et al., 1999, p. 263 a later study based on the IRBP gene instead placed ''Macrotarsomys–Monticolomys'' sister to a clade containing four other nesomyine genera—''Eliurus'', ''Voalavo'', ''Gymnuromys'', and ''Brachytarsomys''.

Description

The Malagasy mountain mouse is a small, mouse-like rodent, and quite different in appearance from most other nesomyines.Carleton and Goodman, 1996, p. 243 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 hairs, 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 metapodials and digits, and long ungual tufts—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 tailCarleton and Goodman, 1996, p. 235 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.Carleton and Goodman, 1996, p. 236 Head and body length is , tail length is , hindfoot length is , ear length is , and body mass is .

The skull is small and delicate. The front part, the rostrum, is narrow and relatively long. The nasal bones are rounded at the front, but blunt at the back. The zygomatic plate—a bony plate at the side of the skull—is narrow and extends back to the front margin of the first upper molar (M1). The jugal bones constitute much of the thin zygomatic arches (cheekbones). The interorbital region, between the eyes, is narrow and hourglass-shaped. There are no crests or ridges on the interorbital region or on the braincase.Carleton and Goodman, 1996, p. 237 The incisive foramina, openings in the front part of the palate, 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, so that the masticatory-buccinator foramen and the foramen ovale accessorium, 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.Carleton and Goodman, 1996, p. 238

The upper incisors have orange enamel 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 at the back of the jawbone. The molars are brachyodont (low-crowned) and bear distinct 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.Carleton and Goodman, 1996, p. 239 The molars are quite similar to those of ''Macrotarsomys'', and differ only in minor details.Carleton and Goodman, 1996, p. 245

Distribution and ecology

The species' range is now known to extend across the mountain ranges of eastern Madagascar from the Tsaratanana MassifMaminirina et al., 2008, p. 716 south to Andohahela, at 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, 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 (''Rattus rattus''). At Andringitra, 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.Carleton and Goodman, 1996, p. 240 At Andohahela, ''Monticolomys'' was found at an altitude of in sclerophyllous forest.Goodman et al., 1999, p. 231 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.Goodman et al., 1999, p. 232 Subfossil remains have been found in Mahajanga Province (northwestern Madagascar). Malagasy mountain mouse is morphologically uniform across its wide distribution.

The Malagasy mountain mouse is nocturnal and solitary and produces litters of up to three offspring.Goodman et al., 2003, table 13.4 It is scansorial, spending time on the ground but also climbing in vegetation. In Andringitra, two specimens were captured on a liana 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 '' Agarista'' fruits.Rasolonondrasana and Goodman, 2006, p. 80

Conservation status

As Malagasy mountain mouse is now known to be a widespread, common species occurring in at least one protected area ( Andringitra National Park; it may also occur in Ankarana Special Reserve), it is listed on the IUCN Red List as "Least Concern". However, fires pose a threat in montane forest and, at lower elevations, its habitat is being converted into agricultural land.

References

Literature cited

* Carleton, M.D. and Goodman, S.M. (1996)
"Systematic studies of Madagascar's endemic rodents (Muroidea: Nesomyinae): A new genus and species from the Central Highlands"
''Fieldiana Zoology'' 85:231–250
* Goodman, S.M., Rakotondravony, D., Schatz, G. and Wilmé, L. (1996)
"Species richness of forest-dwelling birds, rodents and insectivores in a planted forest of native trees: a test case from the Ankaratra, Madagascar"
''Ecotropica'' 2:109–120
* Goodman, S.M., Carleton, M.D. and Pidgeon, M. (1999)
"Rodents of the Réserve Naturelle Intégrale d'Andohahela, Madagascar"
''Fieldiana Zoology'' 94:217–249
* Goodman, S.M., Ganzhorn, J.U. and Rakotondravony, D. (2003). "Introduction to the mammals". pp. 1159–1186 in Goodman, S.M. and Benstead, J.P. (eds.). ''The Natural History of Madagascar''. University of Chicago Press, 1728 pp.
* Jansa, S.A., Goodman, S.M. and Tucker, P.K. (1999)
"Molecular phylogeny and biogeography of the native rodents of Madagascar (Muridae: Nesomyinae): A test of the single-origin hypothesis"
''Cladistics'' 15:253–270
* Jansa, S.A. and Weksler, M. (2004)
"Phylogeny of muroid rodents: relationships within and among major lineages as determined by IRBP gene sequences"
''Molecular Phylogenetics and Evolution'' 31:256–276
*
* Maminirina, C.P., Goodman, S.M. and Raxworthy, C.J. (2008)
"Les micro-mammifères (Mammalia, Rodentia, Afrosoricida et Soricomorpha) du massif du Tsaratanana et biogéographie des forêts de montagne de Madagascar"
''Zoosystema'' 30(3):695–721 (in French)
* Mein, P., Sénégas, F., Gommery, D., Ramanivosoa, B., Randrianantenaina, H. and Kerloc'h, P. (2010)
"Nouvelles espèces subfossiles de rongeurs du Nord-Ouest de Madagascar"
''Comptes Rendus Palevol'' 9(3):101–112 (in French, with abridged English version).
*
* Rasolonondrasana, B.P.N. and Goodman, S.M. (2006). "The influence of fire on mountain sclerophyllous forests and their small-mammal communities in Madagascar". pp. 77–87 in Spehn, E.M., Liberman, M. and Körner, C. (eds.). ''Land Use Change and Mountain Biodiversity''. Boca Raton, Florida: CRC Press, 361 pp.

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Nesomyinae
Mammals of Madagascar
Rodent genera
Taxa named by Michael D. Carleton
Taxa named by Steven M. Goodman
Mammals described in 1996
Endemic fauna of Madagascar
Fauna of the Madagascar subhumid forests