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Petrodromus tetradactylusfour-toed elephant-shrew(Also: four-toed sengi)

By Mary Alice Smith

Geographic Range

The 15 species of Elephant shrews are restricted to Africa (Nicoll and Rathbun 1990). The four toed elephant shrew is found in Central and East Africa from Northern Natal to Kenya and Northwest to the Congo river (Grizmeck 1990). It is also found on the Zanzibar and Mafia Islands (Nowak 1999).

Habitat

Sometimes this animal is found in rocky areas, but usually it prefers thickets and dense forest undergrowth in caesalpinoid forests and woodlands (Kingdon 1997).

Physical Description

This elephant shrew has four toes on the hind foot as opposed to five, hence its common name. The animal is quite beautiful. Its grey to sandy fur is rather long and soft, and it has a touch of orange and yellow hues, sometimes with a wide dark strip on its back and white rings around the eyes. It is named, along with its relatives, for its long trunklike flexible nose used to find a variety of invertebrate prey hiding among the vegetation. However, unique to this species are the long skinny legs that hold the body 3 to 4 cm from the ground.

Elephant shrews are small mammals ranging in weight from 45 to 540 grams. However, the four-toed elephant shrew is one of the largest of the elephant shrews weighing 160 to 280 grams. Its body length ranges from 19 to 23 cm and its tail ranges from 15.5 to 17 cm (Grizmek 1990).

  • Range mass
    160 to 280 g
    5.64 to 9.87 oz
  • Average mass
    205 g
    7.22 oz
  • Range length
    19 to 23 cm
    7.48 to 9.06 in
  • Average basal metabolic rate
    0.852 W
    AnAge

Reproduction

Monogamy is rare in mammals, but is well represented in this order. Most likely an abundance of resources and a monagamous mating sysem suggests a year round mating system.

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Average number of offspring
    1.2
    AnAge

The actual gestation period for this species is unknown but the range for other elephant shrews is 42 to 65 days. What is known for the four-toed elphant shrew is that there is one, sometimes two, young at birth that weigh about 32 grams (Grizmek 1990).The young are born in a highly precocial state, which allows them to run as fast as adults soon after birth (Nicoll and Rathbun 1990). Timing of weaning and sexual maturity is also unknown for this species but the range for weaning is 14 to 25 days and sexual maturity is 35 to 50 days for other elephant shrews (Grizmek 1990).

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

Lifespan/Longevity

It is not known specifically for this species, but the average life span of elephant shrews in general in the wild is up to 4 years (Grizmek's 1990).

Behavior

This species is mostly diurnal but major activity peaks occur just prior to daybreak and and just after nightfall (Rathbun 1979).It makes extensive runways through brush. It usually scurries, but when alarmed it progresses to long jumps (Nowak 1999). It may take refuge in burrows and hollow tree trunks when pursued (Rathbun 1979). When it runs, its tail is pointed upward and it makes rapping sounds with its hind feet. Ants have been noted to respond to this with their own noise enabling this elephant shrew to locate them (Nowak 1999). These elephant shrews sleep outside under the brush rather than in nests. The animal always appear alert (Rathbun 1979). Field studies have shown that monogamous pairs defend territories, female against female and male against male (Rathbun 1979).

Communication and Perception

Food Habits

The long elephant-like snout enables these mammals to find insects within the dense forests of Africa. Termites and ants are preferred. In general, insects make up the largest portion of the diet of this elephant shrew but they eat some plant material as well (Rathbun 1979).

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

Predation

This species is probably hunted by small carnivores, hawks owls and snakes. Avoidance of predators is most likely the reason for their choice of habitat. They are preyed upon by humans, who seek them to eat

Economic Importance for Humans: Positive

Insects being the main portion of the diet of these animals, they are probably important in helping to control pest populations. This may in turn help neighboring farm crops.

  • Positive Impacts
  • controls pest population

Conservation Status

There is little known about the threats facing this elephant shrew, unlike the cases of 7 other macroscelidid species ranging from vulnerable to endangered listed by the IUCN as of 2001. However, habitat modification in their areas of the forests of Africa may be a problem in the future. The good news for this particular elephant shrew is that, since its geographic range is greater than some of its relatives, the risks of becoming endangered are not as high at this time. However, in order to preserve the species deforestation must be minimized, directly affecting the local people of the region and their need to make room for more agricultural lands. The future depends on the establishment of protected areas within these integrated rural land developments, which aim to be beneficial to both the biological diversity and the needs of the local people (Nicoll and Rathbun 1990).

Other Comments

Elephant shrews, a group of about 15 species, small in comparison to other orders of mammals, has always posed a problem for taxonomists. They take their common name from their elephant-like snout and their resemblance to a shrew. Originally they were placed in the order Insectivora in the family Macroscelididae even though the main trait they shared in common with Insectivores is diet. They have been grouped with tree shrews, hares, rabbits, hyraxes and primates in the past. Now it is recognized that this small group constitutes its own order, the Macroscelidea, based on its early split from other mammalian groups and an unusal unique set of features (Grizmeck's 1990).

Contributors

Mary Alice Smith (author), University of Michigan-Ann Arbor, Bret Weinstein (editor), University of Michigan-Ann Arbor.

Glossary

Ethiopian

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

World Map

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.

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

crepuscular

active at dawn and dusk

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.

insectivore

An animal that eats mainly insects or spiders.

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.

scrub forest

scrub forests develop in areas that experience dry seasons.

sexual

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

solitary

lives alone

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).

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.

References

1990. Grizmecks Encyclopedia of Mammals Vol. 1. Mcgraw-Hill Publishing Co..

"Elephant Shrews or Sengis" (On-line). Accessed October 8 ,2001 at http://www.calacademy.org/RESEARCH/bmammals/eshrews/index.html.

"Macroscelidae" (On-line). Accessed October 8, 2001 at http://www.gisbau.uniroma1.it/amd/amd241b.html.

ICUN, 2001. "ICUN redlist" (On-line). Accessed October 10,2001 at http:www.redlist.org/.

Kingdon, J. 1996. East African Mammals an Allan of Evolution in Africa Vol. 2 part A. Chicago: University of Chicago Press.

Kingdon, J. 1997. Kingdon field Guide to African Mammals. San Diego, London, Boston, NY, Sydney, Tokyo, Toronto: Academic Press, Hancourt Brace and Company Publishers.

Nicoll, M., G. Rathbun. 1990. African Insectivora and Elephant Shrews. Gland, Switzerland: IUCN.

Nowak, 1999. Walker's Mammals of the World 6th Edition. Baltimore, Maryland: Johns Hopkins University Press.

Rathbun, G. 1979. The Social Structure and Ecology of Elephant-Shrews. Berlin and Hamburg: Verlag Paul Parey.

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