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Graphiurus surdussilent dormouse

By Thomas Berry

Geographic Range

Silent dormice are found in western Africa, including southern Cameroon, Equatorial Guinea, Gabon, and north-eastern and south-central portions of the Democratic Republic of the Congo. The full extent of their geographic range remains unknown. (Schlitter, 2008)

Habitat

Silent dormice prefer moist lowland forests, specifically those classified by White (1983) as the wetter variety of the Guineo-Congolian rainforest. Only one specimen has been found in the drier type of Guineo-Congolian rainforest. They are agile climbers and largely arboreal. (Holden, 1996; White, 1983)

  • Range elevation
    0 to 560 m
    0.00 to 1837.27 ft
  • Average elevation
    347 m
    1138.45 ft

Physical Description

Silent dormice have compact bodies, and their relatively short, furred tails are frosted brown. Their coat is short and silky. The dorsal pelage is grayish-brown and composed of overhairs and short, fine guard hairs with no intermixed layer of underhairs. The hairs of the ventral pelage are dark gray and tipped with a white buff. Silent dormice have short, wide arboreal feet with six plantar pads. Compared to other species of Graphiurus, silent dormice have small ears, about 5 mm shorter than those of other South African dormice. Their faces are distinctive, with dark, mask-like markings around the muzzle and dark rings around the eyes. Silent dormice are not particularly sexually dimorphic. Females have four pairs of mammae: one pectoral, one postaxillary, and two inguinal. (Dollman, 1912; Holden, 1996)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    18 to 34 g
    0.63 to 1.20 oz
  • Average mass
    25 g
    0.88 oz
  • Range length
    87 to 110 mm
    3.43 to 4.33 in
  • Average length
    99 mm
    3.90 in

Reproduction

Little information is available concerning the reproductive behavior of silent dormice, as their behavior has rarely been observed in the wild. Members of the genus Graphiurus, however, are territorial and solitary in general. When the summer breeding season begins, male African dormice become highly aggressive toward other males, suggesting polygyny. (Nowak, 1999; Webb and Skinner, 1994)

In African dormice, most breeding occurs during the wet summer months (October through February). Normal litter size is between 3 and 4, but female rock dormice and woodland dormice give birth to as many as 6. (Webb and Skinner, 1994)

Average gestation length in woodland dormice, the closest relative of silent dormice, is about 24 days. At birth, woodland dormice weigh about 3.5 g. They reach sexual maturity the summer after their first hibernation. (Lodel, 2011; Webb and Skinner, 1994)

  • Breeding interval
    African dormice breed one or two times each year, usually during the summer months
  • Breeding season
    Breeding occurs in summer, from October through February.
  • Range number of offspring
    1 to 6
  • Average number of offspring
    3

Little information is available regarding the parental investment of silent dormice. Newborns are altricial and, in most African dormice, they become independent after 4 to 6 weeks. Mothers provide protection and nursing in nests in shrubs and among the branches of trees. Paternal investment of African dormice is likely low to nonexistent, but no information is available on the subject. (Lodel, 2011; Nowak, 1999)

  • Parental Investment
  • altricial
  • female parental care
  • 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 specifically regarding the lifespan of silent dormice in the wild. It is likely they have a lifespan similar to that of other dormice, averaging just over 4 years. Silent dormice been recorded to live 5 years and 9 months in captivity. (Lodel, 2011; Nowak, 1999; Webb and Skinner, 1994)

  • Range lifespan
    Status: captivity
    69 (high) months

Behavior

Silent dormice are primarily nocturnal and arboreal, although they can often be found on the ground. In some particularly dense forests, African dormice exhibit diurnal behavior. African dormice create globular nests in the branches of trees and shrubs made of grass, leaves, or lichen. No information is available regarding the specific hibernation patterns of silent dormice. Individuals found in southern or central parts of Africa, hibernate during the winter, but individuals collected from western Africa did not enter states of torpor when exposed to low temperatures. (Lodel, 2011; Stuart and Stuart, 2001; Webb and Skinner, 1994)

Home Range

Little information is available regarding the size of the average home range of silent dormice. A close relative, spectacled dormice, occupies 13.9 hectares (males) and 8.5 hectares (females) on average. In spectacled dormice, adult pairs occupy the most favorable parts of the territory and their young, once independent, disperse to the less ideal parts of the home range. (Nowak, 1999)

Communication and Perception

Silent dormice have excellent visual, auditory, and tactile senses. Typical vocalizations include whistles, chirping noises, various other twittering sounds, and a "surprisingly loud shriek" (Nowak, 1999). Woodland dormice, the closest relative of silent dormice, use scent marks to indicate territories and makes warning vocalizations to defend territories. Territorial encounters between male spectacled dormice involve loud vocalizations, raised claws, and threatening displays with their bushy tails. (Lodel, 2011; Nowak, 1999; Webb and Skinner, 1994)

Food Habits

Silent dormice are omnivores. They eat grains, seeds, nuts, fruits, insects, eggs, and even other small rodents. (Nowak, 1999; Webb and Skinner, 1994)

  • Animal Foods
  • mammals
  • eggs
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • leaves
  • seeds, grains, and nuts
  • fruit
  • flowers

Predation

No information is available specifically regarding predators of silent dormice. However, owls are the primary predators of woodland dormice and at least 19 species of owl are endemic in the geographic range of silent dormice. In general, African dormice tend to have few predators because of their nocturnal and arboreal natures. (Fenton and Fleming, 1976; Lodel, 2011)

When attacked, silent dormice bite with sharp incisors, vocalize loudly, and make threatening displays with bushy tails. Dormice are able to regrow their tails when lost. (Nowak, 1999; Vaughan, et al., 2000)

Ecosystem Roles

Given their dietary habits, silent dormice likely function as seed dispersers. They also probably play an important role in insect population dynamics and perhaps in owl population dynamics, if owls are in fact the primary predator of silent dormice as they are for the woodland dormice. Silent dormice are primary, secondary, and sometimes even higher-level consumers. (Nowak, 1999; Webb and Skinner, 1994)

  • Ecosystem Impact
  • disperses seeds

Economic Importance for Humans: Positive

Because of their small size, African dormice in general have a relatively minor economic impact on humans. However, the human consumption of dormice for food is well-documented in Africa. (Grzimek, 2004)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

Dormice sometimes make themselves a nuisance by raiding poultry yards for food. African dormice can sometimes be found living in human habitations, especially in the upholstery of old furniture, but this occurs less frequently now because of competition with introduced rats. (Nowak, 1999)

Woodland dormice are vectors for bubonic plague and monkeypox. Given the extremely close relationship between woodland dormice and silent dormice, it seems likely that silent dormice may also be carriers of those diseases. (Lodel, 2011)

  • Negative Impacts
  • injures humans
    • carries human disease
  • crop pest
  • household pest

Conservation Status

Not enough data are available to assign G. surdus a conservation status, they are considered data deficient according to the IUCN Red List. (Schlitter, 2008)

Other Comments

Silent dormice are not actually silent, they make quite a few vocalizations. When Dollman discovered the species in 1912, he chose the name to emphasize the small size of its ears. Although Dollman (1912) and Allen (1939) listed silent dormice as their own species, Misonne (1974) combined Graphiurus surdus and Graphiurus murinus into a single species. In 1981 Robbins and Schlitter (1981) listed Graphiurus surdus as its own species once again in a report on Cameroonian dormice, and Holden (1996) revised Graphiurus surdus in a report on Sub-Saharan dormice. (Allen, 1939; Dollman, 1912; Holden, 1996; Misonne, 1974; Robbins and Schlitter, 1981)

Contributors

Thomas Berry (author), Yale University, Eric Sargis (editor), Yale University, Rachel Racicot (editor), Yale University, Tanya Dewey (editor), 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

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.

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.

female parental care

parental care is carried out by females

food

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

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).

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

omnivore

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

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.

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

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

solitary

lives alone

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.

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

Allen, G. 1939. A checklist of African mammals. Bulletin of the Museum of Comparative Zoology, 83: 1-763.

Dollman, J. 1912. Seven new African dormice. Journal of Natural History, 9(51): 312-320.

Fenton, M., T. Fleming. 1976. Ecological Interactions between Bats and Nocturnal Birds. Biotropica, 8(2): 104-110.

Grzimek, B. 2004. Grzimek's Encyclopedia of Mammals. Farmington Hills, MI: Gale.

Holden, M. 1996. Systematic Revision of Sub-Saharan African Dormice (Rodentia: Myoxidae: Graphiurus) Part 1: An Introduction to the Generic Revision, and a Revision of Graphiurus Surdus. American Museum Novitates, 3157: 1-44.

Lodel, J. 2011. "Graphiurus murinus" (On-line). Animal Diversity Web. Accessed April 30, 2012 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Graphiurus%20murinus.html.

Misonne, X. 1974. Part 6: Order Rodentia. Pp. 1-39 in J Meester, W Setzer, eds. The Mammals of African: An Identification Manual. Washington, D.C.: Smithsonian Institution Press.

Nowak, R. 1999. Walker's Mammals of the World. Baltimore, MD: The Johns Hopkins University Press.

Robbins, L., D. Schlitter. 1981. Systematic status of dormice (Rodentia: Gliridae) from southern Cameroon, Africa. Annals of Carnegie Museum, 50: 271-288.

Schlitter, D. 2008. "Graphiurus surdus" (On-line). IUCN Red List of Threatened Species. Version 2011.2. Accessed February 15, 2012 at www.iucnredlist.org.

Stuart, C., T. Stuart. 2001. Field Guide to Mammals of Southern Africa. Cape Town, South Africa: Struik.

Vaughan, T., J. Ryan, N. Czaplewski. 2000. Mammalogy. Stamford, CT: Thomson Learning, Inc.

Webb, P., J. Skinner. 1994. The Dormice (Myoxidae) of southern Africa. Hystrix, the Italian Journal of Mammalogy, 6: 287-293.

White, F. 1983. The vegetation of Africa, a descriptive memoir to accompany the UNESCO/AETFAT/UNSO vexation map of Africa. UNESCO, Natural Resour. Res., 20: 1-356.

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