Definitions

jerboa

jerboa

[jer-boh-uh, jer-]
jerboa, name for the small, jumping rodents of the family Dipodidae, found in arid parts of Asia, N Africa, and SE Europe. Jerboas have extremely long hind feet and short forelegs; they always walk upright or hop like kangaroos. A jerboa can hop faster than a person can run, and a single leap may carry it more than 6 ft (1.8 m). Jerboas have long silky fur, buff colored above and pale below; members of most species have a black face mask and tail tuft. They have large eyes and long ears. The combined head and body length is between 2 and 8 in. (5-20 cm), depending on the species; the tail is usually somewhat longer than the body. When the animal sits, the tail is used as a prop. Solitary, nocturnal animals, with a low tolerance for heat, jerboas spend the day in individual burrows with plugged entrances. In the northern parts of their range they hibernate; some jerboas of the true deserts aestivate. They feed on plant matter, especially seeds, and insects. They do not drink, but survive on water obtained from food or produced by their own metabolism. The similar appearing kangaroo rat and jumping mouse of North America are not of the same family as the jerboa. There are about 25 jerboa species, 22 of them in Asia. They are classified in 10 genera of the phylum Chordata, subphylum Vertebrata, class Mammalia, order Rodentia, family Dipodidae.

Jerboas are the bulk of the membership of the family Dipodidae; they are small jumping desert rodents of Asia and northern Africa that resemble mice with a long tufted tail and very long hind legs. The small forelegs are not used for locomotion. In general, Asiatic jerboas have five toes on their hind feet and African jerboas have three; the shapes of their ears vary widely between species. Jerboa fur is long, soft and silky. Diet varies considerably: some are specialist seed, insect, or plant eaters, others are omnivores. Jerboas obtain energy by eating plants.

The English word jerboa may have been derived from the similar sounding Arabic word jerbu'a or Garbu'a (جربوع) or the Hebrew word yarboa (יַרְבּוֹעַ) which denote this animal.

The ancestors of the modern jerboas probably separated from the more generalised rodents about 8 million years ago on the arid plains of Turkmenistan, Kazakhstan and Mongolia, and then spread to Europe and northern Africa. With the exception of Europe, where they died out, this remains their current range.

Their ability to hop is presumed to be an adaptation to help them escape from predators, and perhaps to assist with the longer journeys a desert-living animal must make to find food. Although jerboas are not closely related to the hopping mice of Australia or the kangaroo rats of North America, all three groups have evolved a similar set of adaptations to life in the deep desert.

Jerboas are nocturnal. During the heat of the day, they shelter in burrows. They create four separate types of burrow: two temporary, and two permanent. The temporary burrows are plain tubes: those used to escape from predators during the night are just deep, unsealed and not camouflaged; the permanent daytime burrows are well-hidden and sealed with a plug of sand to keep heat out and moisture in, and are long.

Permanent burrows often have multiple entrances. They are much more elaborate structures with a nesting chamber. The winter burrows have food storage chambers below ground level, and a hibernation chamber an astonishing down.

Perhaps the best-known species is the Lesser Egyptian Jerboa (Jaculus jaculus) which occupies some of the most hostile deserts on the planet. It does not drink at all, relying on its food to provide enough moisture for survival. Found in both the sandy and stony deserts of north Africa, Arabia and Iran, this small creature aestivates (analogous to hibernation) during the hottest summer months, and has the ability to leap a full metre to escape a predator.

Three species are considered threatened: the Five-toed Pygmy Jerboa (classed 'VU' vulnerable), the Thick-tailed Pygmy Jerboa (classed 'VU' vulnerable), and a rare species only recently captured on film in the deserts of Mongolia and China, the Long-eared Jerboa (classed 'EN' endangered). Many other species have been placed in a "lower risk" category, and one species (Thomas's Pygmy Jerboa) lacks the data for assessment.

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