NesomyidaeAfrican and Malagasy endemic rats and mice

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Diversity

The family Nesomyidae is a diverse group of African rodents that has recently proven to be even more diverse than originally thought, with the discovery of two new genera and species since 1995 (Carleton and Goodman 1996, 1998). Overall, this family encompasses 61 species and 21 genera in six subfamilies: the Cricetomyinae (African pouched rats), the Delanymyinae (swamp mice), the Dendromurinae (climbing mice), the Mystromyinae (white-tailed rat), the Nesomyinae (Malagasy rats and mice), and the Petromyscinae (African rock mice). (Carleton and Goodman, 1996; Carleton and Goodman, 1998; Musser and Carleton, 2005)

Geographic Range

Nesomyid rodents range throughout sub-Saharan Africa and Madagascar. (Corbert, 1984)

Habitat

Nesomyids occupy a wide range of habitats, including forests, shrublands, grasslands, savanna, agricultural fields, and wetlands. They live in both moist and dry habitats and span the tropical, subtropical, and temperate zones. Some are found in montane habitats at altitudes up to 4,300 meters. (Corbert, 1984; IUCN, 2004; Kingdon, 1974; Nowak, 1999)

Physical Description

A survey of the physical characteristics of nesomyid species gives an idea of just how diverse this group is. The wide array of physical characteristics in this group reflects the wide array of habitats and lifestyles to which they have become adapted. Nesomyids are rat-like, vole-like or gerbil-like in overall appearance. Tail lengths range from more than twice the length of the head and body to less than half the length of the head and body, and ear lengths vary as well, from very long relative to the head to very short. In overall size, nesomyids range from the tiny Delany's swamp mouse, with a head and body length of 50 to 63 mm and a weight of 5.2 to 6.5 g, to the hefty African giant pouched rats, which can grow to 450 mm in length and weigh up to 2.8 kg. In some species, males weigh more than females, and in others, there is no detectable sexual dimorphism. Most nesomyids are thickly furred and they span a range of colors, including various shades of browns and grays. Some have nearly naked prehensile tails, and others have well-furred tails that may appear almost bushy and have tufted tips. One subfamily, the Cricetomyinae, has cheek pouches; the others do not. (Kingdon, 1974; Nowak, 1999)

  • Sexual Dimorphism
  • sexes alike
  • male larger

Reproduction

The mating system of nesomyids is largely a mystery, although some species have been reported to live in pairs, suggesting a monogamous mating system, and others are solitary or live in small colonies, suggesting a polygynous or polygynandrous mating system. (Nowak, 1999)

Nesomyids vary widely in their reproductive habits, as they do in all of their life-history characteristics. Many live in areas that experience marked dry seasons and breed only during the wet season, when food is readily available. Others breed at any time of the year. Litter sizes may be as small as one and as large as ten young. (Kingdon, 1974; Nowak, 1999)

Most female nesomyids build nests in which they raise their young. In some species, males live with their mates and help build nests and protect their offspring. Characteristics such as time to weaning and independence are highly variable within this group. Those nesomyid species that have been reared in captivity have altricial young, with relatively slow development. One species, the Malagasy giant rat (Hypogeomys antimena), has young that stay with the parents for more than one breeding season. (Kingdon, 1974; Nowak, 1999; Sommer, 2000)

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

Lifespan/Longevity

As is the case with many rodents, nesomyids have short lifespans in the wild. Most probably do not live more than two years, but lifespan may be considerably longer in captivity. (Kingdon, 1974; Nowak, 1999)

Behavior

Nesomyids range from exclusively arboreal species to exclusively terrestrial species. Many are adept climbers, and even those that are mainly terrestrial may forage in shrubs or small trees. Some are exlusively nocturnal, some are exclusively diurnal, and some are active for at least part of the night and day. They either dig burrows or use burrows made by other animals or tree cavities in which they often build nests and store food. None are reported as being highly social, although some may live in pairs or small family groups, and many are solitary. Degree of territoriality varies, as does degree of sedentariness: some have been reported to migrate between different habitats with the changing of the seasons. Others cope with hot, dry seasons by aestivating in their burrows. (Kingdon, 1974; Nowak, 1999)

Communication and Perception

All nesomyids perceive the world using vision, hearing, smell, and touch, but the relative importance and the acuteness of each of these senses varies among species. The evolution of certain modes of communication is closely tied with sensory abilities, and thus, communication among nesomyids is probably highly variable as well, with different species depending to varying degrees on visual, acoustic, chemical, and tactile cues. (Kingdon, 1974; Nowak, 1999)

Food Habits

The food habits within this family range from strictly herbivorous to strictly insectivorous, with varying degrees of omnivory in between. Foods eaten by nesomyid species include seeds, roots, stems, nuts, berries, fruit, leaves, insects, small reptiles, bird eggs, bird nestlings, crabs, and snails. Many nesomyid species, especially those that are primarily granivorous, create food caches in their burrows. (Kingdon, 1974; Nowak, 1999)

Predation

As small to medium-sized rodents, nesomyids are potential prey for a large array of predators, including mammalian carnivores, snakes, eagles, and owls. Many nesomyid species avoid predation by building nests in inaccessible burrows and relying on their speed and agility to escape. (Kingdon, 1974; Nowak, 1999)

Ecosystem Roles

Given their range of food habits, it is apparent that nesomyids as a group, and in some cases even individual nesomyid species, occupy several trophic levels, including those of primary, secondary, and tertiary consumer. Also, as mentioned above, they are prey for a variety of mammalian, reptilian, and avian predators. Because many nesomyid species include seeds and fruits as a primary component of their diet, these rodents may be important seed dispersers. Finally, nesomyids are parasitized by fleas, ticks, earwigs, and nematodes. (Durette-Desset, et al., 2002; Hubbard, 1972; Kingdon, 1974; Nowak, 1999)

  • Ecosystem Impact
  • disperses seeds
Commensal/Parasitic Species

Economic Importance for Humans: Positive

Some nesomyid species, including those in the genus Steatomys and the Gambian rat, Cricetomys gambianus, are prized as food items by local peoples. Gambian rats are also kept as pets by rodent enthusiasts. Additionally, the species Mystromys albicaudatus is bred in captivity and used for disease research. (Hallett and Meester, 1971; Kingdon, 1974; Nowak, 1999)

Economic Importance for Humans: Negative

One nesomyid species, Cricetomys gambianus, is a pest in urban areas, where it inhabits sewers alongside Rattus. A few species carry the plague. (Hubbard, 1972; Kingdon, 1974; Nowak, 1999)

  • Negative Impacts
  • injures humans
    • carries human disease

Conservation Status

The IUCN lists three species in this family as critically endangered (Eliurus penicillatus, Macrotarsomys ingens, and Dendromus kahuziensis), four as endangered (Eliurus majori, Hypogeomys antimena, Delanymys brooksi, and Mystromys albicaudatus), four as vulnerable (Gymnuromys roberti, Dendromus lovati, Dendromus oreas, and Steatomys jacksoni), two as near threatened (Beamys major and Beamys hindei), three as lower risk (Brachyuromys betsileoensis, Brachyuromys ramirohitra, and Eliurus webbi), and five as having deficient data (Dendromus vernayi, Dendroprionomys rousseloti, Leimacomys b\\u00fcttneri, Prionomys batesi, and Megadendromus nikolausi). The major threat to most of these species is habitat destruction and fragmentation caused by human activities such as agriculture and logging. Although the range of the family as a whole is broad, many of the individual species in the family are endemic to particular locations, which makes them especially vulnerable to habitat loss. This is especially true of the Malagasy rodents, the nesomyines, as they are all endemic and all subjected to extreme habitat pressures. Research on the ecology of many nesomyid species is ongoing, in the hopes of preserving suitable habitat where these rodents can persist. (IUCN, 2004; Kingdon, 1974; Nowak, 1999)

  • IUCN Red List [Link]
    Not Evaluated

Contributors

Allison Poor (author), University of Michigan-Ann Arbor, Tanya Dewey (editor), Animal Diversity Web.

Glossary

Ethiopian

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

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

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.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

crepuscular

active at dawn and dusk

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

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.

fertilization

union of egg and spermatozoan

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

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.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

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).

marsh

marshes are wetland areas often dominated by grasses and reeds.

migratory

makes seasonal movements between breeding and wintering grounds

molluscivore

eats mollusks, members of Phylum Mollusca

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

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

nocturnal

active during the night

omnivore

an animal that mainly eats all kinds of things, including plants and animals

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

polygynous

having more than one female as a mate at one time

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.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

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.

solitary

lives alone

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

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.

year-round breeding

breeding takes place throughout the year

References

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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.

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Musser, G., M. Carleton. 2005. Superfamily Muroidea. D Wilson, D Reeder, eds. Mammal Species of the World. Washington, DC: Smithsonian Institution Press.

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