Elephant shrew

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

Elephant shrews, or jumping shrews, are small insectivorous mammals native to Africa, belonging to the family Macroscelididae, 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. Nonetheless, elephant shrews are not classified with the superficially similar true shrews, but are ironically 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.

They are widely distributed across the southern part of Africa, and although common nowhere, 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.

Characteristics

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. They vary in size from about 10 cm to almost 30 cm, from just under 50 g to over 500 g. The short-eared elephant shrew has an average size of 150 mm (5.9 in). Although the size of the trunk varies from one species to another, all are able to twist it about in search of food. Their lifespans are about two and a half to four years in the wild. They have large canine teeth, and also high-crowned cheek teeth like those of ungulates. Their dental formula is 1-3.1.4.23.1.4.2-3

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 make use of natural crevices, or make leaf nests.

Short-eared elephant shrews inhabit the dry steppes and stone deserts of southwestern Africa. They can even be found in the Namib Desert, one of the driest regions of the earth. 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 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.

Feeding habits

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.

Evolution

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.

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 elephant shrews with tenrecs and golden moles as well as certain mammals previously presumed to be ungulates, including hyraxes, sirenians, aardvarks and elephants.

Elephantulus sp., Frankfurt Zoo

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

The 19 species of elephant shrew are placed in four genera, one of which is 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
      • Namib round-eared sengi, M. flavicaudatus
      • Etendaka round-eared sengi, M. micus
      • Round-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

References

• 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.