Horse jumper
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Horse Jumper ( Allactaga ) |
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| F. Cuvier , 1836 |
The horse jumpers ( Allactaga ) are a genus of jerboa that are named for their size and jumping ability.
features
The largest of all jerboa belong to this genus, but some species are rather small. Depending on the species, the fur is gray, sandy brown or reddish brown on top; the underside is white.
With the exception of one species, all horse jumpers have five toes. The two outer toes are stunted, so that there are only three fully developed and functional toes. There is a comparable arrangement in the deviating species, the four-toed jerboa, which also has three strong toes, with only one stunted toe at their side.
The eyes are enlarged, as is typical for night animals. The rabbit-like ears, which stand upright and are almost as long as the head, are also noticeably large.
distribution and habitat
Two types of horse jumpers occur on European soil: the small horse jumper, whose western limit of distribution is in the Volga region , and the large horse jumper, which is distributed eastwards from Moscow and Kiev today. These two are the smallest and the largest species in the genus. The main area of distribution of the genus is Central Asia. There are horse jumpers in Anatolia , Syria , Iraq , Iran , Pakistan and Afghanistan , in the Asian part of Russia , in the Central Asian states of the former Soviet Union, in Mongolia , Manchuria and in Xinjiang . They inhabit deserts, semi-deserts and steppes with little vegetation.
The deviant four-toed jerboa is the only species that lives in Africa. Their habitat are coastal salt marshes in Egypt and Libya .
Way of life
construction
The Eurasian horse jumpers dig large building systems for various purposes. Four different types of construction have been demonstrated for the Great Horse Jumper: a residential building for the summer, a temporary second building, an escape tunnel for emergencies, and a winter building for hibernation . The residential building has a central chamber, which is about 70 to 150 cm below the surface and is connected to the outside via a 3 m long tunnel. The females pad this chamber with nesting material when they are expecting offspring. Next to the main entrance there is often another escape tunnel to the outside. The winter building has a central chamber at a depth of up to two and a half meters.
Most of the smaller species dig similar burrows. The burrows of the Little Horse Jumper are also deep, although the mounds of earth at the entrances are hardly bigger than the burrowing beetles. The most complex is the construction of the Severtzov jerboa, which connects several chambers with each other via tunnels up to 5 m long.
The four-toed jerboa also digs burrows, but these are only created for a short time and only consist of blind tunnels no longer than 150 cm.
Activity and diet
Like all jerboa, horse jumpers are nocturnal . They then leave their burrows and slowly wander around. Only when they are startled do they use their full bounce and flee in a zigzag. They perform sentences over a meter. The little horse jumper can escape speeds of 48 km / h, which is extraordinary for a rodent. The search for food leads the great horse jumper to plants whose seeds he prefers to eat. It never seems to eat insects, while the Mongolian horse jumper feeds mainly on insects. The little horse jumper has a balanced diet of insects and plant material.
Hibernation
Not all horse jumpers hibernate. Lowland populations living far in the south have no reason for this. The Central and North Asian species, on the other hand, are all winter sleepers. The rest period lasts from September to April at the longest.
Reproduction
Usually horse jumpers are loners who only come together to mate. The females can have offspring two or three times a year. There are one to eight cubs in the litter, but usually three or four. In the little horse jumper, these remain with the mother for about 30 days and are sexually mature at three and a half months. It is therefore possible for a little horse jumper born in spring to give birth to their own kittens before their first hibernation. The great horse jumper has a longer development time and does not mate until it is two years old. The life expectancy of a horse jumper is only in rare exceptional cases more than four years.
Systematics
The horse jumpers are classified in the subfamily Allactaginae within the jerbo . There are eleven species, which are divided into three sub-genera. The first two sub-genera are collectively referred to as five-toed jerboa.
- Subgenus Allactaga
- Little horse jumper , Allactaga elater , West and Central Asia
- Euphrates jerboa , Allactaga euphratica , Western Asia
- Iranian horse jumper , Allactaga firouzi , southwest. Iran
- Hotson jerboa , Allactaga hotsoni , south-east. Iran, Afghanistan, Pakistan
- Great horse jumper , Allactaga major , western and central Russia, Ukraine
- Severtzov jerboa , Allactaga severtzovi , Central Asia
- Turkey Horse Jumper , Allactaga williamsi , Anatolia
- Subgenus Orientallactaga
- Balikun jerboa , Allactaga balikunica , Mongolia
- Gobi jerboa , Allactaga bullata , Mongolia
- Mongolian horse jumper , Allactaga sibirica , Central Asia
- Subgenus Scarturus
- Four-toed jerboa , Allactaga tetradactyla , Egypt, Libya
The name Allactaga jaculus is very often found for the great horse jumper, but it is an invalid wrong combination. Occasionally the Bobrinski jerboa ( Allactodipus bobrinskii ) is assigned to this genus.
In the 2017 rodent volume of the Handbook of the Mammals of the World , Scarturus becomes an independent genus with the following species: Syrian horse jumper ( Scarturus aulacotis ), small horse jumper ( S. elater ), Euphrates horse jumper ( S. euphraticus ), Hotson's jerboa ( S. hotsoni ), four- toed jerboa ( S. tetradactylus ), Vinogradow's horse jumper ( S. vinogradovi ) and Turkey horse jumper ( S. williamsi ).
Man and horse jumper
The great horse diver is considered a pest in many places because it attacks grain fields or opens pumpkins and melons to get at their kernels. Many of the other species, on the other hand, are too rare to cause harm. The Iranian horse jumper is even listed as severely threatened by the IUCN . It is known only from a tiny area in southwestern Iran, and its total population is estimated to be less than 250 individuals. The four-toed jerboa is not considered threatened, but it also has a very small distribution area. Drainage of the salt marshes that provide its habitat could quickly doom the species to extinction. The nominate form of the Euphrates jerboa, the subspecies Allactaga euphratica euphratica , which is only widespread in Saudi Arabia and is almost extinct there , is also to be regarded as threatened .
literature
- Ronald M. Nowak: Walker's Mammals of the World. 2 volumes. 6th edition. Johns Hopkins University Press, Baltimore MD et al. 1999, ISBN 0-8018-5789-9 .
supporting documents
- ↑ Don E. Wilson, Thomas E. Lacher Jr., Russell A. Mittermeier (eds.): Handbook of the Mammals of the World. Volume 7 - Rodents II. Lynx Edicions, 2017, ISBN 978-84-16728-04-6 , p. 97.
