DelanymyinaeDelany's swamp mice

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Diversity

Delanymyinae is an Old World nesomyid subfamily consisting of just a single genus and species, Delany's swamp mice (Delanymys brooksi). (Musser and Carleton, 2005)

Geographic Range

Delany's swamp mice are native to east central Africa, including southwestern Uganda, Zaire, Rwanda, and the eastern portion of the Democratic Republic of the Congo. (Nowak, 1999)

Habitat

The preferred habitat of Delany's swamp mice is sedge marsh in montane and bamboo forests, at elevations from 1,700 to 2,625 meters. (Carleton and Musser, 1984; Nowak, 1999)

Physical Description

Delany's swamp mice are small nesomyid rodents. The head and body length ranges from 50 to 63 mm, the tail length ranges from 87 to 111 mm, and the body weight is about 6 grams. The tail is about twice as long as the head and body. Delany's swamp mice have delicate, gracile bodies with long hind feet and digits. The tail is semiprehensile, and the fifth toe is semiopposable. Four of the digits on the front feet bear claws, and the hind feet have claws on all five digits. The fur on the back is russet, the chin is whitish, and the belly is a warm, buff color. The bases of the hairs are grayish. The coat is thick, soft, and woolly. The scaly, bicolored tail is covered in thin hairs, and the soles of the feet lack fur except near the bases.

The delanymyine dental formula is 1/1, 0/0, 0/0, 3/3 = 16. The upper incisors are orthodont and the upper molars lie in parallel rows. The brachydont molars have three roots in the upper jaw and two roots in the lower jaw. The first two molars are about the same size, and the third molar is about a third the size of the others. The molar surface is marked by a series of alternating cusps, and the anterior crests of the first upper molars are large and not bicuspid. The first and second upper molars have distinct mesolophs and mesostyles. There is a labial cusp on the cingulum of the first and second molars of the lower jaw, and there is no posterior cingulum of the molars of the upper jaw. The small mandible has thin coronoid processes. The rostrum is short, and the delicate skull has a high, rounded braincase. The area between the orbits is narrow to moderately wide and has smooth edges. There are no temporal ridges. The zygomatic arches are narrow and delicate, and the infraorbital foramina are relatively large. The zygomatic plates are narrow and do not extend anterior to the dorsal zygomatic roots. The incisive foramina terminate before the anterior borders of the molar rows, and the bony palate terminates in a deep V-shape before the posterior borders of the molar rows. The mesopterygoid fossa is narrow and the anterior portion is constricted, and the pterygoid fossae are long, wide, and almost flat. There are small sphenopalatine vacuities. The middle lacerate foramina are small. There is no alisphenoid strut, and the accessory foramen ovale, masticatory foramen, and buccinator foramen are all merged into a single opening. There is no stapedial foramen, and the internal maxillary artery is a branch of the internal carotid artery. The auditory bullae are relatively inflated, and there is a large opening in the lateral surface of each mastoid bulla. The soft palate has three ridges in the premolar region and four ridges in the molar region. (Carleton and Musser, 1984; Nowak, 1999)

Reproduction

The mating system of Delany's swamp mice has not been reported.

Not much information is available on reproduction in Delanymyinae. Two females were collected with three embryos each, and a nest was found containing four young. (Nowak, 1999)

Delany's swamp mice rear their young inside of globular nests that they make out of grass and place in low shrubs. Being mammals, females nurse their offspring, but no further information is available on the investment of these mice in their young. (Nowak, 1999)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

No information is available on the lifespan of delanymyines.

Behavior

Delany's swamp mice build small, round nests out of grass. Each nest has one or two entrances and is situated in a low shrub. They are nocturnal, and, as their common name would suggest, they are well-adapted for climbing, with semi-prehensile tails, long digits, and semi-opposable toes. (Carleton and Musser, 1984; Nowak, 1999)

Communication and Perception

Delanymyines have eyes and ears, so they no doubt perceive the world through vision and hearing. They probably also receive tactile and chemical signals, as do all mammals. No information is available on how these rodents communicate.

Food Habits

Delany's swamp mice feed exclusively on seeds. (Nowak, 1999)

Predation

There have been no reports of predation on delanymyines, nor have any anti-predator adaptations been reported. However, these mice probably remain vigilant and use their agility to escape predation. Likely predators include raptors, snakes, and small to medium-sized mammalian carnivores.

Ecosystem Roles

Delanymyines are primary consumers, and they are no doubt consumed by other animals, although no one has reported predation on climbing swamp mice.

Economic Importance for Humans: Positive

There are no known positive impacts of these rodents on humans, although these mice are undoubtedly integral parts of healthy ecosystems in areas they inhabit.

Economic Importance for Humans: Negative

There are no known negative impacts of these rodents on humans.

Conservation Status

Delanymys brooksi is listed as endangered by the IUCN due to the destruction of habitat in its already small geographic range. (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

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

forest

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

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

internal fertilization

fertilization takes place within the female's body

marsh

marshes are wetland areas often dominated by grasses and reeds.

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

sexual

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

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

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

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., 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.

Hayman, R. 1962. A new genus and species of African rodent. Revue de Zoologie et de Botanique Africaines, 65: 129-138.

IUCN, 2004. "2004 IUCN Red List of Threatened Species" (On-line). Accessed June 02, 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.

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. Family Muridae. D Wilson, D Reeder, eds. Mammal Species of the World. Washington, D.C.: Smithsonian Institution Press.

Nowak, R. 1999. Walker's Mammals of the World, vol. 2. Baltimore and London: The Johns Hopkins University Press.

Petter, F. 1967. Particularities dentaires des Petromyscinae Roberts 1951 (Rongeurs, Cricetides). Mammalia, 31: 217-224.

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.