NesomyinaeMalagasy rats

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Diversity

The subfamily Nesomyinae is a diverse group of muroid rodents endemic to Madagascar. There are 23 nesomyine species in nine genera. (Musser and Carleton, 2005)

Geographic Range

Nesomyine rodents are only found on Madagascar. (Carleton and Musser, 1984; Nowak, 1999)

Habitat

Nesomyines live in a wide variety of habitats, including grasslands, wet meadows, sandy coastal forests, dry scrublands, and wet or dry inland forests. They range from sea level to 2,400 meters in elevation. (Carleton and Musser, 1984; Nowak, 1999)

Physical Description

Nesomyines are characterized by their morphological and ecological diversity. Typically they are medium to large gerbil-like, vole-like, or rat-like rodents. They measure 80 to 350 mm in head and body length and their tails range from 60 to 250 mm. Nesomyines weigh 21 to 1,500 grams. In some species, females weigh less than males, in other species, there is no sexual dimorphism. Nesomyine tails are short to long, naked to moderately furred, and sometimes tufted. Some have prehensile tails. The hind feet range from wide and short to narrow and long, and most have no hair on the soles. The pelage is long and soft or thick and woolly. It is sandy brown, reddish, or gray on the dorsum and yellowish white, white, or gray on the venter. Most nesomyines have large eyes and prominent ears and whiskers.

The nesomyine dental formula is 1/1, 0/0, 0/0, 3/3 = 16. The incisors are opisthodont. The molars are rooted, have a biserial cusp arrangement, and range from brachydont to hypsodont. In most species, the third molar is equal in size to the first two molars. Nesomyines have strong zygomatic arches with large jugals. Most species have ventrally constricted infraorbital foramina. There is a prominent interparietal bone. The bony palate is wide and smooth and bears one pair of posterior palatine foramina. The pterygoid fossae are flat and level with the bony palate. Most species have a large postglenoid foramen, and all species have an accessory tympanum and malleus of parallel construction. Nesomyines have 13 thoracic and 7 lumbar vertebrae. There are three circumvallate papillae on the tongue, and the stomach consists of a single chamber. The soft palate bears three premolar and five intermolar ridges. (Carleton and Musser, 1984; Nowak, 1999)

  • Sexual Dimorphism
  • sexes alike
  • male larger

Reproduction

The mating system has not been studied for all nesomyine species, but at least one species, the Malagasy giant rat (Hypogeomys antimena), is known to be monogamous and mate for life. (Sommer, 2000)

The reproductive behavior of some nesomyine species is entirely unknown. Therefore, the following may or may not apply to the entire group. Nesomyines reproduce during the wet season, and some species have just a single litter per year. Gestation lasts up to 138 days and there are one to four young per litter. Sexual maturity is not reached until the age of two years in some species. (Nowak, 1999; Sommer, 2000)

Female nesomyines nurse their offspring for up to six weeks in a sheltered spot such as a tree cavity or underground nest chamber. In monogamous species, males may risk predation themselves by keeping watch for danger and protecting their offspring. Also, in those species that live in family groups, such as Hypogeomys antimena, young females remain with their parents for more than a year, not dispersing until after their parents have a new litter. (Sommer, 2000)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • male
  • pre-independence
    • protecting
      • male
  • post-independence association with parents

Lifespan/Longevity

The lifespan of nesomyines has not been reported.

Behavior

Nesomyines are a diverse group, including terrestrial and arboreal rodents. They are modified for cursorial, scansorial, and saltatorial locomotion. They build nests in tree cavities or in underground burrows. These burrows may be quite complex with multiple entrances and chambers. Some nesomyines live in small family groups, with an adult pair and their offspring inhabiting one burrow system. These family groups are territorial, excluding strangers from their home ranges. Other species have permanent home ranges that overlap with one another. Most nesomyines are nocturnal, though a few species are diurnal, crepuscular, or active any time of the night or day. (Carleton and Musser, 1984; Nowak, 1999; Sommer, 2000)

Communication and Perception

Nesomyines probably sense their environment through vision, hearing, touch, smell, and taste, as do most mammals. Many have large eyes and ears and long vibrissae, suggesting keen visual, auditory, and tactile abilities. Some nesomyine species live in small family groups and give alarm calls to warn their offspring when predators approach. (Nowak, 1999; Sommer, 2000)

Food Habits

These rodents are herbivores that feed on fruit, seeds, berries, roots, and stems. They are not known to cache their food. (Nowak, 1999)

Predation

Nesomyines are preyed upon by snakes, raptors, and mammalian carnivores. Some species give alarm calls and quickly retreat into underground burrows when danger threatens. (Sommer, 2000)

Ecosystem Roles

Nesomyines are primary consumers that provide food for upper level consumers such as carnivorous mammals and snakes. They are parasitized by nematodes and ticks. (Durette-Desset, et al., 2002; Hoogstraal, et al., 1967; Sommer, 2000)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

There are no known positive effects of nesomyines on humans.

Economic Importance for Humans: Negative

There are no known negative effects of nesomyines on humans.

Conservation Status

This subfamily consists of endemic species with restricted ranges that are highly vulnerable to habitat loss. As a result, 8 of the 23 species in this group are on the IUCN's Red List of Threatened Species. Two of these species are critically endangered (Eliurus penicillatus and Macrotarsomys ingens), two are endangered (Eliurus majori and Hypogeomys antimena), one is vulnerable (Gymnuromys roberti), and three are lower risk (Brachyuromys betsileoensis, Brachyuromys ramirohitra, and Eliurus webbi). One species, the endangered Malagasy giant rat (Hypogeomys antimena), is being bred and studied in captivity at the Jersey Zoo by the Durrell Wildlife Conservation Trust. (Durrell Wildlife Conservation Trust, 2005; IUCN, 2004)

  • IUCN Red List [Link]
    Not Evaluated

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Allison Poor (author), University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

acoustic

uses sound to communicate

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

crepuscular

active at dawn and dusk

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

frugivore

an animal that mainly eats fruit

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

island endemic

animals that live only on an island or set of islands.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

saltatorial

specialized for leaping or bounding locomotion; jumps or hops.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Carleton, M., S. Goodman. 1998. New taxa of nesomyine rodents (Muroidea: Muridae) from Madagascar's northern highlands, with taxonomic comments on previously described forms. Pp. 163-200 in S Goodman, ed. A Floral and Faunal Inventory of the Eastern Slopes of the Reserve Speciale d'Anjanaharibe-Sud, Madagascar: With Reference to Elevational Variation. Fieldiana: Zoology, 90: 1-246.

Carleton, M., S. Goodman. 1996. Systematic studies of Madagascar's endemic rodents (Muroidea: Nesomyinae): a new genus and species from the central highlands. Pp. 231-256 in S Goodman, ed. A Floral and Faunal Inventory of the Eastern Slopes of the Reserve Naturelle Integrale d'Andringitra, Madagascar: With Reference to Elevational Variation. Fieldiana: Zoology, 85: 1-319.

Carleton, M., G. Musser. 1984. Muroid rodents. Pp. 289-379 in S Anderson, J Jones Jr., eds. Orders and Families of Recent Mammals of the World. New York: John Wiley and Sons.

Chaline, J., P. Mein, F. Petter. 1977. Les grandes lignes d'une classification évolutive des Muroidea. Mammalia, 41: 245-252.

Durette-Desset, M., J. Lehtonen, V. Haukisalmi. 2002. Trichostrongylina (Nematoda) from Malagasy Muridae. II. Description of two new species of Heligmonina (Heligmonellidae) in Nesomys rufus and Eliurus tanala. Parasite, 9 (2): 127-133.

Durrell Wildlife Conservation Trust, 2005. "Malagasy giant jumping rat" (On-line). Accessed July 05, 2005 at www.durrellwildlife.org.

Ellerman, J. 1940. The Families and Genera of Living Rodents, vol. I. London: British Museum (Natural History).

Ellerman, J. 1941. The Families and Genera of Living Rodents, vol. II. London: British Museum (Natural History).

Hoogstraal, H., G. Uilenberg, J. Klein. 1967. Haemaphysalis (Rhipistoma) anoplos. New species. A spurless tick of the elongata group (Ixodoidea Ixodidae) parasitizing Nesomys rufus (Rodentia) in Madagascar. Journal of Parasitology, 53 (5): 1103-1105.

IUCN, 2004. "2004 IUCN Red List of Threatened Species" (On-line). Accessed July 05, 2005 at www.redlist.org.

Jansa, S., M. Weksler. 2004. Phylogeny of muroid rodents: relationships within and among major lineages as determined by IRBP gene sequences. Molecular Phylogenetics and Evolution, 31: 256-276.

Michaux, J., A. Reyes, F. Catzeflis. 2001. Evolutionary history of the most speciose mammals: Molecular phylogeny of muroid rodents. Molecular Biology and Evolution, 18(11): 2017-2031.

Miller, G., J. Gidley. 1918. Synopsis of supergeneric groups of rodents. Journal of the Washington Academy of Science, 8: 431-448.

Musser, G., M. Carleton. 1993. Family Muridae. Pp. 501-753 in D Wilson, D Reeder, eds. Mammal Species of the World. Washington, D. C.: Smithsonian Institution Press.

Musser, G., M. Carleton. 2005. Superfamily Muroidea. D Wilson, D Reeder, eds. Mammal Species of the World. Baltimore and London: The Johns Hopkins University Press.

Nowak, R. 1999. Walker's Mammals of the World, vol. II. Baltimore and London: The Johns Hopkins University Press.

Simpson, G. 1945. The principles of classification and a classification of mammals. Bulletin of the American Museum of Natural History, 85: 1-350.

Sommer, S. 2000. Sex-specific predation on a monogamous rat, Hypogeomys antimena (Muridae: Nesomyinae). Animal Behavior, 59: 1087-1094.

Steppan, S., R. Adkins, J. Anderson. 2004. Phylogeny and divergence-date estimates of rapid radiations in Muroid rodents based on multiple nuclear genes. Systematic Biology, 53(4): 533-553.