Elephant shrew

Elephant shrews Fossil range: Early Oligocene–Recent PreЄ Є O S D C P T J K Pg N
Short-eared elephant shrew (Macroscelides proboscideus)
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Infraclass: Eutheria (unranked) Afroinsectiphilia Superorder: Afrotheria Order: Macroscelidea Butler, 1956 Family: Macroscelididae Bonaparte, 1838
Genera
Rhynchocyon Petrodromus Macroscelides Elephantulus

Elephant shrew (or elephant-shrew) is the common name for any of the small insectivorous mammals comprising the order Macroscelidea, whose living members are characterized by a rodent- or opossum-like appearance, with hind limbs longer than forelimbs, elongated snouts, relatively large eyes and ears, complete auditory bullae, and upper canines with two roots. Also known by the common name of sengis, which helps disassociate them from the true shrews (order Soricomorpha, family Soricidae) and the treeshrews (order Scandentia), extant elephant shrews comprise only one family, Macroscelididae, with four genera and less than 20 species. Elephant shrews are restricted to Africa and, with the notable exception of western Africa and the Sahara region, are found throughout the continent.

Description

Rhynchocyon petersi

Elephant shrews are small, quadrupedal, insectivorous mammals resembling rodents or opossums, with scaly tails, elongated snouts, and rather long legs for their size, which are used to move in a hopping fashion like rabbits. The hind limbs are much longer than the forelimbs, and they have relatively large eyes and ears. they have complete auditory bullae, complete zygomatic arches, and relatively small olfactory lobes in the brain (Myers 2014). Some elephant shrews are brightly colored, with the genus Rhynchocyon including the most colorful elephant shrews (Rathbun 2014). The small species tend to be shades of gray and brown (Rathbun 2014).

Sengis range in size from that of a mouse to that of a large rat or squirrel, from about 10 centimeters to more than 30 centimeters and from 25 grams to 700 grams. The larger adult members of the Rhynchocyon genus range from 350 to 700 grams, with head/body lengths of up to 31 centimeters and tail lengths of up to 25 centimeters (Rathburn 2014). Adults of the Macroscelides may be about 25 grams, while members of Petrodromus may range up to 200 grams. The short-eared elephant shrew has an average size of 150 mm (5.9 in).

Elephant shrews have large canine teeth, and also high-crowned cheek teeth like those of ungulates (Rathbun 1984). The upper canine has two roots (Myers 2014). Their dental formula is ${\tfrac {1-3.1.4.2}{3.1.4.2-3}}$

Elephant shrews have a relatively long digestive tract with a caecum.

Distribution and habitat

Elephant shrews are widely distributed in Africa, with the exception of western Africa and the Sahara region. The Macroscelides genus is found only in southwestern Africa, while most Elephantuuls species are found in southern Africa and eastern Africa. Members of Rhynchocyon are found in eastern and central Africa. Members of Petrodromus are widespread (Rathbun 2014).

Although elephant shrews are not common anywhere, they can be found in almost any type of habitat, from the Namib Desert to boulder-strewn outcrops in South Africa to thick forest. One species, the North African elephant shrew, remains in the semiarid, mountainous country in the far northwest of the continent. Short-eared elephant shrews inhabit the dry steppes and stone deserts of southwestern Africa and even in the Namib Desert, one of the driest regions of the earth.

Behavior, feeding, and life cycle

Although mostly diurnal and very active, they are difficult to trap and very seldom seen; elephant shrews are wary, well camouflaged, and adept at dashing away from threats. Several species make a series of cleared pathways through the undergrowth and spend their day patrolling them for insect life. If disturbed, the pathway provides an obstacle-free escape route.

Elephant shrews are not highly social animals, but many live in monogamous pairs, which share and defend a home territory they mark using scent glands. Rhynchocyon species also dig small conical holes in the soil, bandicoot-style, but others may use of natural crevices, or make leaf nests.

Elephant shrews mainly eat invertebrates, such as insects, spiders, centipedes, millipedes, and earthworms. An elephant shrew uses its nose to find prey and uses its tongue to flick small food into its mouth, much like an anteater. Eating large prey can pose somewhat of a challenge for an elephant shrew. For example, a giant elephant shrew struggling with an earthworm must first pin its prey to the ground with a forefoot. Then, turning its head to one side, it chews pieces off with its cheek teeth, much like a dog chewing a bone. This is a sloppy process, and many small pieces of worm drop to the ground; these are simply flicked up with the tongue. Some elephant shrews also feed on small amounts of plant matter when available, especially new leaves, seeds, and small fruits.

Females drive away other females, while males try to ward off other males. Although they live in pairs, the partners do not care much for each other and their sole purpose of even associating with the opposite sex is for reproduction. Social behaviors are not very common and they even have separate nests. The one or two young are well developed at birth; they are able to run around just a few hours after birth.

Female elephant shrews undergo a menstrual cycle similar to that of human females^{[citation needed]} and the species is one of the very few nonprimate mammals to do so. The elephant shrew mating period lasts for several days. After mating, the pair will return to their solitary habits. After a gestation period varying from 45 to 60 days, the female will give birth to litters of one to three young several times a year. The young are born relatively well developed, but remain in the nest for several days before venturing outside.

After five days, the young's milk diet is supplemented with mashed insects, which are collected and transported in the cheek pouches of the female. The young then slowly start to explore their environment and hunt for insects. After about 15 days, the young will begin the migratory phase of their lives, which lessens the dependency of the young on their mother. The young will then establish their own home ranges (about 1 km²) and will become sexually active within 41–46 days.

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Classification

In the past, elephant shrews have been classified with the shrews and hedgehogs as part of the Insectivora; regarded as distant relatives of the ungulates; grouped with the treeshrews; and lumped in with the hares and rabbits in the Lagomorpha. Recent molecular evidence, however, strongly supports a superorder Afrotheria that unites tenrecs, and golden moles with certain mammals previously presumed to be ungulates, including hyraxes, sirenians, aardvarks and elephants, as well as the elephant shrews.

An elephant shrew from Frankfurt Zoo

A male black and rufous elephant shrew at the National Zoo in Washington, DC

The 17 species of elephant shrew are placed in four genera, two of which are monotypic:

• ORDER MACROSCELIDEA
  • Family Macroscelididae
    • Genus Elephantulus
      • Short-snouted elephant shrew, E. brachyrhynchus
      • Cape elephant shrew, E. edwardii
      • Dusky-footed elephant shrew, E. fuscipes
      • Dusky elephant shrew, E. fuscus
      • Bushveld elephant shrew, E. intufi
      • Eastern rock elephant shrew, E. myurus
      • Karoo rock elephant shrew, E. pilicaudus
      • Somali elephant shrew, E. revoili
      • North African elephant shrew, E. rozeti
      • Rufous elephant shrew, E. rufescens
      • Western rock elephant shrew, E. rupestris
    • Genus Macroscelides
      • Short-eared elephant shrew, M. proboscideus
    • Genus Petrodromus
      • Four-toed elephant shrew, P. tetradactylus
    • Genus Rhynchocyon
      • Golden-rumped elephant shrew, R. chrysopygus
      • Checkered elephant shrew, R. cirnei
      • Black and rufous elephant shrew, R. petersi
      • Grey-faced sengi , R. udzungwensis

A number of fossil species are known, all of them from Africa. They were separate from the similar-appearing order Leptictida. A considerable diversification of macroscelids occurred in the Paleogene. Some, such as Myohyrax, were so similar to hyraxes, they were initially misidentified as belonging to that group, while others, such as Mylomygale, were relatively rodent-like. These unusual forms all died out by the Pleistocene. Although macroscelids have been classified with many groups, often on the basis of superficial characteristics, considerable morphological and molecular evidence now indicates placing them within Afrotheria, probably close to the base of Paenungulata.

External links

• Elephant Shrew. African Wildlife Foundation. Retrieved February 2010.
• Sengis (Elephant-Shrews). California Academy of Sciences. Retrieved October 2012.
• New Species Of Giant Elephant-shrew Discovered. Science Daily (February 2008). Retrieved February 2010.

, in the order Macroscelidea, whose traditional common English name comes from a fancied resemblance between their long noses and the trunk of an elephant, and an assumed relationship with the shrews (family Soricidae) in the order Insectivora. It has become plain that the elephant shrews are not to be classified with the superficially similar true shrews, but ironically are rather more closely related to elephants and their kin within the newly recognized Afrotheria; the biologist Jonathan Kingdon has proposed they instead be called sengis, a term derived from the Bantu languages of Africa.

References

ISBN links support NWE through referral fees

• Murata Y, Nikaido M, Sasaki T, Cao Y, Fukumoto Y, Hasegawa M, Okada N. Afrotherian phylogeny as inferred from complete mitochondrial genomes. Mol Phylogenet Evol. 2003 Aug;28(2):253-60.
• Murphy WJ, Eizirik E, Johnson WE, Zhang YP, Ryder OA, O'Brien SJ. Molecular phylogenetics and the origins of placental mammals. Nature. 2001 February 1;409(6820):614-8.
• Tabuce R, Marivaux L, Adaci M, Bensalah M, Hartenberger JL, Mahboubi M, Mebrouk F, Tafforeau P, Jaeger JJ. Early Tertiary mammals from North Africa reinforce the molecular Afrotheria clade. Proc Biol Sci. 2007 May 7;274(1614):1159-66.

• Myers, P. http://animaldiversity.ummz.umich.edu/accounts/Macroscelidea/ Macroscelidea: Elephant-shrews)]. Animal Diversity Web. Retrieved April 21, 2014.

• Rathbun, G. B. 2014. Sengis (elephant-shrews). Sengis.org. Retrieved April 21, 2014.

• Rathbun, G. B. 1984. Elephant-shrews. In D. Macdonald (ed.), The Encyclopedia of Mammals. New York: Facts on File. ISBN 0871968711.

• Simons, E. L., P. a. Holroyd, and T. M. Bown. 1991. Early tertiary elephant-shrews from Egypt and the origin of the Macroscelidea. Proc. Natl. Acad. Sci. USA 88: 9734-9737.

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