Class Mammalia Order Rodentia Suborder Sciurognathi Family Dipodidae
Pygmy to medium-sized quadrupedal or bipedal rodents with hind limbs slightly or much longer than forelimbs; long tails and eyes and external ears ranging in size; coarse or soft brown, brownish-yellow or jonquil fur; a dichromatic, black-and-white banner tail tip characteristic of many jerboa species specialized for the fast bipedal gallop
Number of genera, species:
15 genera, 49-51 species
Inhabitants of forests, meadows, steppe and desert plains and mountain regions
Endangered: 4 species; Vulnerable: 4 species; Lower Risk/Near Threatened: 6 species; Data Deficient: 4 species
North America, Northern Africa, Arabian Peninsula, Europe, and Asia
North America, Northern Africa, Arabian Peninsula, Europe, and Asia
Traditional classifications based mostly on morphological similarities consider two related families: Dipodidae, including all jerboas, and Zapodidae, including jumping mice and birch mice. The family of jerboas include three subfamilies (Euchoreutinae, Cardiocraniinae, and Dipodinae), and the family of jumping and birch mice include two subfamilies (Zapodinae and Smintinae = Sicistinae). Vorontsov et al. in 1971 divided jerboas into four subfamilies (Euchoreutinae, Cardiocraniinae, Allactaginae, and Dipodinae), and Gam-barianin in 1983 divided them into three families (Euchore-utidae, Cardiocraniidae, and Dipodidae with two subfamilies, Allactaginae and Dipodinae). The recent revision of plylo-genetic relationships of all groups of jerboas, jumping mice, and birch mice, based on palaeontological data and complex morphological comparisons, suggests one superfamily Dipodoidea with four families: Zapodidae, Smintidae (with subfamilies Euchoreutinae and Smintinae), Dipodidae (with subfamilies Cardiocraniinae, Paradipodinae, and Dipodinae), and Allactagidae. The position of Euchoreutes is not clearly defined, and there are reasonable arguments to consider long-eared jerboa to represent a separate family. Considering Dipodidae as an extended interpretation, one must be aware of long-term independent evolution of jumping mice, birch mice, and at least three lineages of jerboas. Formal resemblance of long-eared jerboa (subfamily Euchoreutinae), five-toed jerboas (subfamily Allactaginae), and three-toed jerboas (subfamilies Cardiocraniinae, Paradipodinae, Didodi-nae) is considered now to be a result of parallel evolution of bipedality in arid open and flat landscapes. Among three-toed jerboas very deep differences, signifying early divergence, exist between pygmy jerboas (Cardiocraniinae), genus Paradi-pus, and true three-toed jerboas (Dipodinae). Fossil remains of Dipodidae have been discovered from the Eocene in North America and from the Oligocene in Eurasia. Three-toed jerboa fossils from the middle Miocene were discovered in Asia, and five-toed jerboa fossils from the middle Miocene were unearthed in North Africa as well as upper Miocene specimens from Europe and Asia.
Birch mice and jumping mice are small, mouse-like quadrupedal rodents with fairly long semi-prehensile tails. Jumping mice hind limbs are moderately elongated, whereas birch mice have no elongation. Jerboas are small to medium-sized bipedal, nocturnal rodents adapted to run fast in sparse vegetation. Both birch and jumping mice have relatively small and narrow heads, and jerboas have relatively large heads with wide muzzles and flat snouts. Jerboas also have big eyes, long vibrissa, and auricles that vary in size from relatively short among three-toed jerboas to extremely long in long-eared jer-
boa (Euchoreutes naso). In pygmy jerboas (Cardiocraniinae), the auricle is tubular. Among jerboas, the neck is weakly pronounced or not pronounced at all; the neck vertebrae are fused in the Cardiocraniinae, Paradipodinae, and Dipodinae, but unfused in the other subfamilies.
All jerboas have short and compact bodies with short fore-limbs and long strong hind limbs. The tail is usually long, ending as a rule, but not always, with the dichromatic black-and-white banner. The brush of long hairs may resemble a bird feather. Among pygmy jerboas (Cardiocraniinae) and in Pygeretmus platyurus, a specialized representative of five-toed jerboas, the tail is relatively short, bannerless, and fat. Fore-limbs have five fingers. Claws are short and blunt in birch mice, jumping mice, and five-toed jerboas, or long and narrow in three-toed jerboas. Hind feet have five, four, or three toes. If toes are more than three, the first and the fifth toes are much shorter than three middle ones. In Allactaga tetradactyla the first toe is absent. The three central bones of the hind foot are fused to form a single cannon bone among all fast running jerboas (except in Cardiocraniinae). The pelage is coarse in the Smintinae and Zapodinae with light or dark brown or brownish yellow back hair and paler, lighter brown hair on the ventrum. Jerboas have dense, soft earthen-colored fur with lighter, sand-colored fur on the back and white on the belly. The dental formula of the Dipodidae is (I1/1 C0/0 P0-1/0 M3/3) X 2 = 16 or 18. The upper incisors are weakly grooved in the Zapodinae, but smooth in the other subfamilies. Premolar is intent for reduction. Molars are either low- (Smintinae) or high-crowned (other subfamilies) and have adult roots.
Thirteen birch mice species are endemic to Eurasia (from Austria in Europe to Sakhalin island in the Far East). Five species inhabit mostly plains. All others are present in moun tain terrains (Caucasus, Altai, Tien Shan, mountains of Central China, Pakistan, Kashmir). Jumping mice (genus Eoza-pus) occur in Central China (Quinghai, southern Gansu, Ningxia, Shaanxi, western Sichuan, northwestern Yunan provinces). Another two genera of jumping mice, Zapus (Z. hudsonius, Z. princeps, Z. trinotatus) inhabit North America from southern Alaska to southwestern United States, and Napaeozapus (N. insignis) from southeastern Manitoba to Labrador and Pennsylvania and south along Appalachian Mountains to northern Georgia. Jerboas are confined to open semi-arid and arid lands of the Palaeoarctic region. The range covers North Africa, Eastern Europe, Central, middle, and southwestern Asia, including Arabia.
Their origin is considered connected with Asia where they demonstrate the greatest species and genera diversity. By the middle Miocene, jerboas penetrated Africa but did not diverge. Ranges of nine genera are restricted to Eurasia and ranges of two genera are distributed in arid lands of both Eurasian and North African continents. Euchoreutinae and Cardiocraniinae are strictly Asian groups. Asia accounts for 30-31 species; Europe five species; Africa three species. Two centers of species diversity of jerboas in Asia, one connected with deserts of Middle Asia (Uzbekistan, Turkmenistan, and southwestern and southern portion of Kazakhstan), and the other with deserts of Mongolia and China. Euchoreutes naso, Salpingotus kozlovi, Stylodipus andrewsi, Allactaga bullata, and A. balicunica are endemic to Mongolian-Chinese deserts. Salpingotus heptneri, Paradipus ctenodactylus, Eremodipus lichtensteini, Allactodipus bobrinskii, and Allactaga severtzovi are endemic to desert middle Asia. Pygeretmus shitkovi and P. platyurus are endemic to cold deserts of Kazakhtan. Species diversity in Asia decreases from subzone of cold deserts to the south (subtropical deserts) and to the north (steppe). Jerboas did not cross the Indus River. Accordingly, there are no jerboas in the Thar Desert of India. Three species of jerboas (Allactaga tetradactyla, Jaculus jaculus, and J. orientalis)
common for tree-toed jerboas, whereas five-toed jerboas usually inhabit areas with hard clay soils. Jerboas that are adapted for locomotion on soft sandy substrate have brushes of long hard hairs on sides of their toes to stabilize the foot on the soft sand. When the three-toed jerboas run, the distal part (all toes) of their hind limbs contacts the substrate surface. In contrast, when five-toed jerboas run, they touch the hard substrate only by the tall compact callus on top of the central toe. The second and the fourth toes are shorter and mostly act as shock absorbers (bumpers).
are present in North Africa. Genus Jaculus are also common in deserts located in the Arabian Peninsula, Middle East, Iran, Iraq, and Afganistan.
Birch mice inhabit forests, thickets, moors, meadows, and steppe. In the mountain regions, they occur in the forest and subalpine belts. Jumping mice (genus Zapus) inhabit wooded areas, grassy fields, and alpine meadows. They are common in the thick vegetation bordering streams, ponds, and marshes. The woodland jumping mouse (N. insignis) inhabits spruce-fir and hemlock-hardwood forests where it prefers moist, cool places with dense vegetation. It is common along streams in bogs and swamps. The Chinese jumping mouse (E. setchuanus) is found near stream banks in cool forests at high mountain elevations of 9,840—13,120 ft (3,000-4,000 m). Jerboas occupy all type of desert habitats from moving sands to clay depressions and rocky-gravel plateau and dry mountain slopes. Up to five species can be seen in one habitat, and the local fauna can account for eight species.
Many species are habitat specific while others are less selective. Some selective species include Paradipus ctenodactylus that inhabits top ridges of moving sands (barkhans) in the deserts of Turkmenistan and Uzbekistan; Allactodipus bobrin-skii that inhabits clay and rocky-clay plains covered with the thin sandy-gravel wash; and Pygeretmus pumilio, an inhabitant of clay depressions with hard surface covered by sparse vegetation of succulents. In general, sandy habitats are more
Birch mice and jumping mice are quadrupeds. During ground travel, they often climb tussock grass, shrubs, and bushes, curling the tail for additional support around branches and twigs. Jumping mice hop up to 3.3 ft (1 m) high and 6 ft (1.8 m) long. They are also a good swimmers (Zapus, Na-paeozapus). All jerboas are bipedal, but differ in capacity to run fast for a long distance. The best runners among such five-toed jerboas as Allactaga major or A. severtzovi, can maintain a speed of 25 mph (40 kph). Pygmy jerboas do not increase their speed over 6 mph (9 kph). Normally, the birch mice and jumping mice use a quadrupedal walk when moving slowly. When startled, however, they often take several leaps, using their powerful hind legs for propulsion; the forelimbs are used just for support when the body contacts the substrate
(quadrupedal hop). The jumping mouse can make three to four jumps without touching the substrate with their fore-limbs. While the pygmy jerboa moves slowly with short hops, it also can touch the substrate with forelimbs. When it increases its speed, the hind feet work simultaneously, and the forelimbs never touch the substrate. Pygmy jerboas cannot run long distances. When chased they demonstrate cryptic behavior and stretch out on the substrate in a shadow of small shrub or hollow. They never use shelter burrows to escape danger.
When running quickly, five-toed and three-toed jerboas push off the substrate with one hind foot after another. Such non-synchronous propulsion provides additional acceleration to the bipedal gallop. Large-sized and fast species escape danger by running for a distance of hundreds of feet (meters) (Al-lactaga major, A. severtzovi, Paradipus ctenodactylus, Dipus sagitta). The large home range of Paradipus ctenodactylus in the Karakum desert of Turkmenistan may reach 1.2 mi (2 km) in diameter. Smaller forms with relatively weak hind feet range in a diameter often less than of 328 ft (100 m) (Pygeretmus pumilio, P. shitkovi, Stylodipus telum). When moving slowly with short jumps, jerboas are unable to keep position of the body axis stable. Shifts of the body's center of gravity force it to make deep bows after each jump. Because bipedal hopping at low speeds is considered energetically expensive, the best runners among five-toed jerboas and all three-toed jerboas use another gait for slow movements—when foraging, they walk on hind feet as humans do.
Birch mice and jumping mice rarely dig. For shelters they often use space under logs, boards, or roots, or even clumps of vegetation where they build nests of dry leaves and woven grass or moss. The birch mouse (Sicista betulina) often uses hollows in old wood. Sicista also can dig shallow burrows or use burrows built by other species. The woodland jumping mouse (Napaeozapus insignis) also can dig simple burrows, but prefers to occupy old burrows left by other rodents. All species of jerboas dig very well and construct three types of burrows: day (summer) burrows used to sleep during the day time, shelter burrows used to escape predatory attacks in the night time, and wintering burrows used for hibernation. The first and last burrow types, including day burrows where females bear their pups, are similarly constructed and differ mostly in depth and length. Five-toed jerboas dig in a hard soil with their incisors and excavate soil with the help of forelimbs, pulling soil out of the tunnel by the snout. Jerboas start with the digging of the main inclined tunnel. From a point close to the end of the main tunnel chamber it digs a second, steep and narrow tunnel up to the surface, sometimes with one to three cavities and only one outside opening. It is indistinct and usually closed by a plug when the jerboa is in the burrow. Jerboa closes the initial tunnel by the soil dug out from the second hole.
Day burrows of three-toed jerboas are more diverse in construction, but similar in building techniques. In contrast to five-toed jerboas, forelimbs play the predominant role in digging sandy soils by the three-toed jerboas. Three-toed jerboas can build simple daily burrows with only one tunnel in a soft sand. Shelter burrows of five-toed and some three-toed jerboas look like simple short tunnels with open holes used to escape predatory attacks. Burrows contain nest chambers
loosely constructed from dry vegetation or, in the case of the desert jerboa, camel hair.
Birch mice, jumping mice, and most species of jerboas hibernate. Duration of hibernation is taxon dependent and also dependent on geography. Birch mice hibernate up to six, or seven months. The weight loss during the half year hibernation in S. betulina reaches 50%. The body temperature in a hibernating birch mouse can drop to as low as 36°F (2°C). Among the jerboa species breeding only one time in a year, the five-toed pygmy jerboa (Cardiocraniusparadoxus) goes into winter sleep in Mongolia from the end of August up to May of the next year. Species with the spring and fall breeding cycle have shorter hibernation periods. Jerboas inhabiting subtropical deserts do not hibernate, but a state of torpor may continue for several days.
All groups of Dipodidae are nocturnal rodents, although the birch mice and jumping mice can be active in the day time (mostly in the morning or evening). Jerboas are strictly nocturnal and sleep in individual burrows with the entrance closed by a soil plug during the daytime. Pygmy jerboas build plugs with their tail, whereas all other jerboa species use the muzzle. Only in spring is it possible to observe jerboas feeding in dusk before sunrise or immediately after sunset.
Dipodidae are solitary—as a rule, each individual uses its own burrow to sleep in the daytime and to hibernate. At the same time, antagonistic behavior is taxon and dependent upon location. Very little is known about home ranges and social relationships among species of birch mice. In the woodland jumping mouse (Napaeozapus insignis) individuals are highly tolerant of one another. Their home ranges vary from 1 to 9 acres (0.4-3.6 ha), and overlap. For Zapusprinceps in the Colorado mountains, Stinson in 1977 reported very small home ranges (0.4 acres [0.17 ha] for males and 0.2 acres [0.1 ha] for females). Males had overlapping home ranges and were tolerant of one another, whereas females had more exclusive territories. Neighboring individuals tend to share the shelter burrows, although their home ranges can overlap considerably. In many jerboa species, individuals avoid contact with each other within overlapping areas. Only pygmy jerboas, especially Salpingotus crassicauda, seem to be aggressive and territorial.
Jerboas have no well-developed, specific skin glands for scent marking. Specific marking behavior (touching substrate by ano-genital area) is identified in the long-eared jerboa (Eu-choreutes naso). Pygmy jerboas often bathe in sand, and sites of sand bathing can play the role of chemical marks.
Birch mice and jumping mice feed on fungus, nuts, berries, fruits, and arthropods. They, as well jerboas, do not store food. Jerboas represent a diverse spectra of feeding adaptations from carnivory of Euchoreutes naso and Salpingotus ko-
zlovi to granivory-insectivory of Salpingotus crassicauda, granivory of Cardiocranius paradoxus, granivory-folivory of Di-pus sagitta and Stylodipus telum, Eremodipus lichtensteini, A. elater and folivory of Paradipus ctenodactylus and of jerboas of genus Pygeretmus. Some species are omnivorous, feeding on green parts of plants, roots, bulbs, seeds, fruits, and arthropods (Allactaga major, A. sibirica, A. severtzovi, etc.). Based on the data on feeding of birch mice, jumping mice, and pygmy jerboas as well as on the data on teeth structure of extinct and recent Dipodidae, it is plausible that distribution of feeding resources and predation risk are predominant factors in the evolution of bipedal locomotion. In the open, desert-like habitat, the rodent that looks for sparsely distributed energy-rich food items becomes exposed to the predator much more often than in a sheltered, densely vegetated habitat. In such situations, natural selection may support an increase in acceleration of the escape flight at its initial stage, determining the vector of morphological innovations.
Foraging strategies among jerboas are intriguing, particularly among food specialists. For instance, the long-eared jerboa (Euchoreutes naso) can actively locate flying insects by their extremely large, flexible auricles that are close in size to the body length. The long-eared jerboa catches moths by making vertical rushes quick as lightning. The pygmy jerboa (Salpingotus kozlovi) forages at sand dune slopes. Its muzzle has a snout surrounded by a field of dense, long vibrissa oriented to the side. Digging in the sand, it makes small sand-slips and detects arthropods and their larva with both the nose and vib-rissa field. Its very large middle ear cavities probably facilitate hearing ground-born sounds too. The comb-toed jerboa (Paradipus ctenodactylus) feeds on young green twigs of succulent bushes that grow on slopes of sand dunes. It makes ver-
years for Sicista, Zapus, and Napaeozapus. In respect to breeding biology, jerboas can be classified into two groups. The first includes species that breed only one time during the warm season (in spring or summer). Two consecutive litters in a season is rare. This group includes Euchoreutes naso, Car-diocraniusparadoxus, Stylodipus telum, S. andrewsi, Allactaga major, A. sibirica, A. balicunica, and Pygeretmus platyurus. The second group includes species that breed in the spring and fall, and can produce three litters in a year: Dipus sagitta, Al-lactaga severtzovi, Allactaga elater, Allactodipus bobrinskii, Pygeretmus pumilio, and P. shitkovi. Juveniles of this group of species, born in spring, can participate in the fall breeding. Juveniles of the first group of species start to breed only in the next year. The litter size of the species that breed only once per year is larger (from two to nine) than in the group that can produce multiple litters annually (from one to eight). Jerboas are polygamous. Gestation is described only for several species, and is rather long, varying from 19-20 days in Stylodipus telum to 25-30 days in Dipus sagitta, and to 28-30 days in Allactaga severtzovi. In many species, pups stay from five to six weeks in the nest burrow before emergence. The reasonable explanation of such a long duration of juveniles' postnatal development is that the motor skills needed for bipedal locomotion must be completely developed before the juvenile leaves the burrow. Soon after emergence pups become independent of their mother. Only in the first nights after they first go out juveniles follow the female. Some species of three-toed jerboas follow each other tail to tail and move in a linear fashion.
tical jumps to cut off a twig and runs with it to the top of the sand dune (barkhan) to feed. Extremely acute hearing and strong hind feet protect this jerboa from predators while in open areas.
Birch mice have a single litter per year with a gestation period of four to five weeks and the duration of parental care four weeks—that is rather long for a very small rodent. Birch mice attain sexual maturity only after hibernation. In Sicista betulina, a single litter contains three to 11 pups. Among jumping mice, Zapus hudsonius is known to produce at least two litters, occasionally three, per year, but Z. princeps and Z. trinotatus have only a single annual litter. The gestation period is 17-23 days, and litter size is two to nine pups with an average of four to six young. Young females of only Z. hud-sonius may be able to produce their own litters in the same season of their birth. In Napaeozapus insignis, females in southern populations give birth twice during the breeding season from early May to early September; in the north one litter per year is more common. The litter size varies from two to seven, averaging approximately 4.5 young. The gestation period is about 23 days, and the newborn pups are weaned at 34 days. Both males and females start to breed only after the first hibernation. Very little is known about reproductive biology of the Chinese jumping mouse (Eozapus setchuanus).
Birch mice and jumping mice are relatively long-lived creatures. The maximum reported lifetime in nature was four
Among birch mice, the IUCN classified Sicista armenica as Critically Endangered. S. caudata is classified as Vulnerable because of progressive loss of its preferred habitat. Among jumping mice, the IUCN designates Eozapus setchuanus as Vulnerable because of destruction of mountain forest habitats. There are two subspecies of Zapus hudsonius with conservation status designated as Endangered (Z. h. preblei) and Vulnerable (Z. g. campestris). Zapus trinotatus orarius was designated by IUCN as Conservation Dependent, being restricted to a very small area on the northern California coast. Among jerboas, the IUCN declared special conservation status for 11 species. Euchoreutes naso and Allactaga tetradactyla were classified as Endangered; A. firouzi as Critically Endangered; Cardiocranius paradoxus and Salpingotus crassicauda as Vulnerable; and S. kozlovi, S. heptneri, Jaculus orientalis, Allac-taga euphratica, Pygeretmus shitkovi, and Allactaga bullata as Lower Risk/Near Threatened.
The recent data from Mongolia suggest that Cardiocranius paradoxus and Allactaga bullata are common, widely distributed species in Mongolia. Another Mongolian species, Eu-choreutes naso is characterized by a low but a stable population density in southern Gobi, where human impact is minimal (Rogovin and Shenbrot, 1995; Sokolov et al., 1996). On the other hand, Salpingotus heptneri must be considered critically endangered. Its range is limited to two small areas of in the northern Kyzylkum desert of Uzbekistan and Kazakhstan. The species has not been observed since the beginning of
1980. Now, due to the catastrophic desiccation of the Aral Sea and changes of the climate in the northern Kyzylkum, the future of this species is unknown and special research is needed.
Two subspecies of Jaculus blanfordi (J. b. turcmenicus and J. b. margianus) are also Endangered—they have small ranges restricted to northern and southern Turkmenistan and to the Kyzylkum Desert in Uzbekistan. Many areas of their typical habitat, the clay depressions and dry river streams between stabilized and semi-stabilized sand ridges, were plowed during 1970-1980. Salpingotus pallidus and Allactaga vinogradovi should be considered vulnerable because of their limited and fragmented ranges. Very little is known about Salpingotus michaelis and S. thomasi from Iran and Afganistan. New species of genus Salpingotus are still possible in Iran, Afganistan and northwestern China.
Birch and jumping mice and jerboas have little significance to humans. In a plague, some jerboas (Stylodipus telum and Allactaga elater) can be invoked into epizootic process. Jerboas play a significant role in desert ecosystems. The density of most abundant species such as Stylodipus telum, Allactaga elater, or Pygeretmuspumilio can reach 40-50 individuals per 2.5 acres (1 ha).
1. Comb-toed jerboa (Paradipus ctenodactilus ); 2. Long-eared jerboa (Euchoreutes naso); 3. Little five-toed jerboa (Allactaga elate) 4. Southern birch mouse (Sicista subtilis); 5. Bobrinski's jerboa (Allactodipus bobrinskii); 6. Five-toed pygmy jerboa (Cardiocranius paradoxus ); 7. Hairy-footed jerboa (Dipus sagitta). (Illustration by Patricia Ferrer)
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