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Myosorex variusforest shrew

By Jency Joseph

Geographic Range

Myosorex varius is a forest shrew that is native to the Ethiopian region of the world. The shrew is endemic to the southern portion of Africa. Of all the 15 different species of South African forest shrews, M. varius is one of the most widely distributed species. It can be found in Limopopo Province, Gauteng, Mpumalanga, the north-eastern Free State, throughout KwaZulu-Natal, Eastern and Western Cape, where M. varius is found inland to Murraysberg and Beaufort West, as well as coastally from Western Cape to the northwestern parts of North Cape. They are found as far north as Pot Nolloth. This species is also found in Lesotho and the Highveld and Middleveld regions of Swaziland. The areas encompass much of the southern region of Africa. Myosorex varius is sympatric throughout much of its geographic range with Myosorex cafer. (Apps, 2000; Rowe-Rowe and Meester, 1982; Skinner and Chimimba, 2005)

Habitat

Myosorex varius is a terrestrial mammal that can be found at elevations ranging from sea level to 1,740 m of elevation. It is called the forest shrew because it is most often found in forest habitats. Myosorex varius can be found in moist, densely vegetated areas, ranging from primary forest to montane grassland to the Highveld, which is a high plateau region of inland South Africa. It is often the first small animal to appear after a burn. (Apps, 2000; Rowe-Rowe and Meester, 1982; Skinner and Chimimba, 2005)

  • Range elevation
    0 to 1,740 m
    0.00 to ft

Physical Description

Myosorex varius ranges from dark grey to a brown. Venter hair tends to be grey with white tips and its feet are an off-white color. Its tail is dark-brown dorsally and pale underneath. Total body length averages 12.6 cm, with an average tail length of 4.3 cm, which is about 46% of its entire body length. Mysorex varius is sexually dimorphic in the KwaZulu-Natal/Drankensberg region, with males being significantly larger than females in regards to total mass as well as head and body size; however, populations in other regions, such as Eastern Cape, exhibit little to no sexual dimorphism. Body-size is correlated to habitat altitude, as higher altitude individuals tend to be much smaller than those resident to lower altitudes. Myosorex varius is endothermic and bilaterally symmetric. It has a basal metabolic rate of 38.9 J/g hr. The forest shrew’s body temperature is highly variable, ranging from 33.2 to 38.3 degrees C. It can withstand temperatures as low as 6 degrees C by increasing heat production. (Apps, 2000; Brown, et al., 1997; Skinner and Chimimba, 2005)

  • Sexual Dimorphism
  • sexes alike
  • male larger
  • Average mass
    12 g
    0.42 oz
  • Average length
    12.6 cm
    4.96 in

Reproduction

The mating system of Myosorex varius has not been documented. Single breeding pairs are often found in nests. Many species of shrew (e.g., least shrews) are promiscuous. Myosorex varius has never been successfully bred in captivity. (Apps, 2000; Bedford, et al., 1998; Bedford, et al., 2004)

Myosorex varius breeds seasonally from September to March, which correlates to the wet seasons of spring and summer. Although it is known to be a seasonal breeder, pregnant females are found year round, with the exception of December. At higher altitudes, breeding season may be delayed for a month due to lower ambient temperatures. Males court female by chasing and grabbing potential mates by the loose skin surrounding the neck. Litters range in size from 2 to 5 pups, with an average of 3. Neonates weigh about 1g at birth. For the first 5 days after parturition, offspring nipple cling. Then, they begin caravanning, which initially consists of the offspring grabbing the mother’s fur with their teeth in a cluster. At about 10 to 13 days old, young form a chain by grabbing ahold of one another, while the lead pup grabs ahold of the mother. Weaning is complete by 20 to 25 days after birth. Females exhibit post-partum estrus and often comes into heat within hours after giving birth. (Apps, 2000; Bedford, et al., 1998; Bedford, et al., 2004)

  • Breeding season
    Myosorex varius breeds during the wet season of spring and summer.
  • Range number of offspring
    2 to 5
  • Average number of offspring
    3
  • Range weaning age
    20 to 25 days
  • Average weaning age
    24 days

Prior to weaning, Myosorex varius females provide food and protection for their offspring. Once pups are fully weaned, they become independent of their mother's care. (Apps, 2000)

  • Parental Investment
  • female parental care
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

This African forest shrew has a lifespan ranging from 12-16 months in the wild. (Apps, 2000; Rowe-Rowe and Meester, 1982)

  • Range lifespan
    Status: wild
    12 to 16 hours
  • Typical lifespan
    Status: wild
    12 to 16 months

Behavior

African forest shrews are predominantly nocturnal, showing a sharp rise in activity at dusk and sharp decline at dawn. However, diurnal activities have also been documented occasionally active during the daytime. Evidence suggests that African forest shrews are nocturnal during the summer months but becomes diurnal during mid-winter. This allows the shrew to be in its warm nest during the coldest hours of the night. During the day, they stay in their nests for only a couple hours at a time, leaving for brief periods to find food and defecate. The feces of the forest shrews is highly pungent. When the shrew does leave its nest, it is extremely cautious and remarkably aggressive. African forest shrews are active burrowers, using their front claws and their long pointed snout. The insides of their burrows and nests are spherical. Forest shrews often modify abandoned burrows of mole rats, rather than excavate their own. If they do create their own nest, it is typically a shallow nest. Nests are constructed from grass, and contain two to four entrances. Typically, nests contain a single breeding pair of shrews. In general, shrews sleep on their bellies with their head tucked under their chest and their feet and tail tucked in under the body. Forest shrews, like most soricids is territorial and aggressive. (Apps, 2000)

Home Range

There is no information available regarding the average home range size of African forest shrews. (Apps, 2000; Wirminghaus and Perrin, 1992)

Communication and Perception

Communication in African Forest shrews is limited. Nesting pairs chatter to each other, and when alarmed or fighting, they may produce a sharp squeak. Forest shrews rely on acoustic, visual, tactile, and chemical cues to perceive their environment. Courting behavior between potential mates consists of a males chasing and catching mates by the nape. Males rely on their sense of smell to determine whether a female is in estrus or not. (Apps, 2000; Skinner and Chimimba, 2005)

Food Habits

Myosorex varius is insectivorous. It is considered an opportunistic feeders and eats most invertebrates it encounters. Evidence suggests that it feeds on at least 7 different types of arthropods including crustaceans, millipedes and centipedes, and arachnids. It frequently drinks small amounts of water. When eating small prey, it first beheads the arthropod and then rapidly bites the insect down the abdomen before beginning to actually eat the animal. When consuming large prey, M. varius throws the insect into the air and breaks off any legs or hind limbs by jerking or twisting them off and then beheads and bites the insect. Cannibalism has been documented in M varius and occasionally consumes carrion of conspecifics or rodents. In captivity, it has been known to eat plants, however, this has never been observed in wild populations. (Apps, 2000; Bedford, et al., 2004; Wirminghaus and Perrin, 1992)

  • Animal Foods
  • mammals
  • insects
  • terrestrial non-insect arthropods
  • aquatic crustaceans
  • Plant Foods
  • leaves

Predation

The main predator of forest shrews is barn owls. However, water mongooses, striped weasels and striped polecats are also significant predators as well. To avoid predation, they only leave their nest to obtain food and to defecate. When they do leave their nest, it only leaves for small amounts of time to avoid contact with predators. When in danger, they let out a sharp squeak to alert their nest mate of the potential threat. (Apps, 2000)

  • Known Predators
    • barn owls, water mongooses, striped weasels, and striped polecats

Ecosystem Roles

Myosorex varius acts as prey to numerous larger mammals. It also serves as a predator to insects and other invertebrates, and as a result, may help control insect pest species. It also acts as a scavenger and eats carrion from dead rodents and conspecifics. It creates creates habitat via shallow burrows in the soil and under rocks. Disturbing soil helps to release nitrogen contents to the surface of the soil, allowing for a diversity of plants to grow. Parasites of this species have not been documented. (Apps, 2000; Wirminghaus and Perrin, 1992)

  • Ecosystem Impact
  • creates habitat

Economic Importance for Humans: Positive

As an insectivore, Myosorex varius likely helps control insect pest species throughout its geographic range. (Apps, 2000)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

There are no known adverse effects of Myosorex varius on humans.

Conservation Status

Myosorex varius is categorized as a species of least concern by the IUCN's Red List of Threatened Species and all other known conservation organizations. Population trends are stable, and there are no major threats to the long-term persistence of this species.

Contributors

Jency Joseph (author), The College of New Jersey, Matthew Wund (editor), The College of New Jersey, John Berini (editor), Animal Diversity Web Staff.

Glossary

Ethiopian

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

World Map

acoustic

uses sound to communicate

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.

carnivore

an animal that mainly eats meat

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

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.

insectivore

An animal that eats mainly insects or spiders.

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

scavenger

an animal that mainly eats dead animals

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

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 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

Apps, P. 2000. Smither's Mammals of Southern Africa: A Field Guide. Cape Town, South Africa: Struik Publishers.

Bedford, J., R. Bernard, R. Baxter. 1998. The 'hybrid' character of the gametes and reproductive tracts of the African shrew, Myosorex varius, supports its classification in the Crocidosoricinae. Journal of Reproduction and Fertility, 112(1): 165-173.

Bedford, J., O. Mock, S. Goodman. 2004. Novelties of conception in insectivorous mammals (Lipotyphla), particularly shrews.. Biological Reviews, 79-4: 891–909.

Brown, C., E. Hunter, R. Baxter. 1997. Metabolism and thermoregulation in the forest shrew Myosorex varius (Soricidae: Crocidurinae). Comparative Biochemistry and Physiology Part A: Physiology, 118(4): 1285-1290.

Rowe-Rowe, D., J. Meester. 1982. Population dynamics of small mammals in the Drakensberg of Natal, South Africa.. Z. Saugetierkunde, 47(6): 347-356.

Skinner, J., C. Chimimba. 2005. The mammals of the southern African subregion. Cambridge: Cambridge University Press.

Wirminghaus, J., M. Perrin. 1992. Diets of small mammals in a southern African temperate forest.. Israel Journal of Zoology, (38)3-4: 353-361.

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