Pygeretmus pumilio
Creators: name: Don E. Wilson
name: Russell A. Mittermeier
name: Thomas E. Lacher, Jr
Publisher: name: Lynx Edicions
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Rodentia
Dipodidae
Pygeretmus
Pygeretmus pumilio

description: 24.
Dwarf Fat-tailed Jerboa
Pygeretmus pumilio
French: Gerboise lievre / German: Zwerg-Fettschwanzspringmaus / Spanish: Jerbo de cola grasa enano
Other common names: Lesser Five-toed Jerboa, Little Earth Hare
Taxonomy. Dipus sibiricus pumilio Kerr, 1792,
Indersk, Atyrau Region, Kazakhstan.
Pygeretmus pumilio is in the subgenus Alactagulus. Five subspecies recognized.
Subspecies and Distribution.
P.p.pumilioKerr,1792—SEuropeanRussia,Kazakhstan,Uzbekistan,Turkmenistan,andNIran.
P.p.bullatoidesShenbrot,1995—SWMongolia(MongolianDzungaria).
P.p.iliensisShenbrot,1995—SEKazakhstan(CIliRiverBasin).
P.p.potaniniVinogradov,1926—EKazakhstan(DzungarianGateandLakeZaysanBasin),NW&NChina(NXinjiangandInnerMongolia[=NeiMongol]),andW&SMongolia.
P. p. selevini Shenbrot, 1995 — E Kazakhstan (from the left bank of Irtysh River near Semey to NE foothills of Chingiz-Tau Mts).
Descriptive notes. Head—body 95-135 mm, tail 125-175 mm, ear 23-31 mm, hindfoot 40-56 mm; weight 30-78 g. Female Dwarf Fat-tailed Jerboas are slightly larger than males. Condylo-basal lengths of skulls are 22:4-27-2 mm, zygomatic breadths are 19-23-3 mm, and maxillary tooth row lengths are 4-3-5-5 mm. Head and dorsum are dim brownish or clayish gray; sides and ventral pelage are pure white; tail is relatively long, with narrow but well flattened banner; and tail banner is tri-colored, with short grayish clay, yellowish ocherous, or whitish basal ring, black or dark brown subterminal field (10-35 mm), and white terminal tuft (10-20 mm). Tailis slightly thickened only in adults in autumn. Toes of hindfeet are naked below or covered with thin, short (3-5 mm) and soft off-white or dark brown hairs not forming brushes; conic calluses at bases of toes are well expressed. Auditory bullae are weakly inflated. Mastoid cavity is extremely small and not subdivided into sections; tympanic cavity is medium-sized.
Front surfaces of incisors are white; incisors are significantly deflected forward. P' is absent in adults, but it often occurs in young, being extremely small with no separate alveolus. Molars are high-crowned, with terraced masticatory surfaces; crown heights of unworn molars are 135-165% of their lengths. Glans penis is lanceolate, flattened, 4-1-5 mm long and 2-1-3-1 mm wide, compressed in dorso-ventral direction, subdivided by deep and wide longitudinal dorsal depression into two lateral lobes; surfaces of lobes are covered by single-vertex, backward-directed aciculae, markedly increasing in size in backward direction; and aciculae are arranged in 12-14 longitudinal rows, with 10-16 aciculae in each row. Os penis (baculum) is absent. Chromosomal complement has 2n = 48 and FN = 92.
Habitat. Semi-desert and desert habitat in patches of sparse saltwort vegetation; in western part of the distribution, only on clay soils; in northern and eastern parts of the distribution, on clay and gravelsoils.
Food and Feeding. The Dwarf Fat-tailed Jerboa is mainly folivorous. Green plant parts dominate its diet in all parts ofits distribution and in almost all seasons, comprising 60-90% by volume. Their relative dominance gradually decreases from spring to autumn in northern parts ofits distribution, but in southern parts, diets vary seasonal with the opposite trend. Seeds can be 8-25% of diets, being most abundant in autumn in the north and in spring in the south. Underground plant parts are typically eaten in small amounts (less than 10%), but in some regions (such as North Aral Desert in Kazakhstan and foothills of Mongolian Altai in Mongolia), they can be 13-19% of diets. Insects are always minor (0-5-5%) parts of the diet.
Breeding. Breeding of the Dwarf Fat-tailed Jerboa has two clear peaks: the first in spring and early summer (March—June) and the second in late summer—autumn (August—=October). Litters have 1-8 young (average range 3-3-9); mean litter sizes increase with age of females: 1-2-3-8 litters in yearlings, 2-1-4-4 in one-year-olds, and 3-4-7 in three-year-olds. One-year-old females have one litter per year, and two-year-old females usually have two litters. Overwintering females can produce up to three litters per year but yearlings only one. Yearlings born in spring are sexually mature in the next autumn at ¢.3 months old; those born in autumn mature at the end of the next spring at ¢.9 months old. Gestation was estimated at 20 days. Young nurse for 35-40 days.
Activity patterns. The Dwarf Fat-tailed Jerboa is crepuscular and nocturnal. Aboveground activity usually starts 40-60 minutes after sunset in spring and autumn and 20-30 minutes after sunset in summer, although some individuals can emerge from burrows several minutes before sunset. Activity ends immediately before sunrise. Activity has 2-3 peaks, in the first one-half, middle, and end of the night. Hibernation lasts 3-5-5-5 months from the end of September-November to February—-April, with interruptions during thaws. Dwarf Fat-tailed Jerboas hibernate in special chambers in winter burrows; temperatures in these chambers are 1-6°C; in nest chambers of winter burrows, temperatures are usually 3-4°C higher than in hibernation chambers; and individuals use nest chambers only during interruptions of hibernation.
Movements, Home range and Social organization. Dwarf Fat-tailed Jerboas move slowly when foraging, using bipedal pacing with alternating support by left and right hindfeet. When running fast, they use asynchronous ricochetjumps. Maximum length ofjump is 95 cm, and maximum running speed is 7-6 m/s. Escape behavior is char-acterized by hiding on the ground’s surface (moonless nights) or by running fast and hiding in a shelter burrow (full-moon nights). Home range sizes vary depending on age, season, and density; mean sizes are 1-1-2 ha for males and 0-4-0-8 ha for females. Home ranges of older individuals are larger than those of younger individuals. Breeding home ranges of males are twice as large as non-breeding home ranges. For females, this trend is in the opposite direction, and home ranges are smallest during late pregnancy and lactation. At low densities, home ranges of females are isolated, and those of males overlap marginally; home range of one adult male usually widely overlaps home ranges of 2-3 females. At high densities, home ranges ofall individuals widely overlap, regardless of sex; each individual actively defendsits own living and shelter burrows. Summer burrows usually consist of the initial tunnelfilled with soil (excavated during construction of main tunnels) and two main tunnels, one horizontal, starting from the main entrance at the ground’s surface closed with soil plug and leading to the emergency exit, and one sloping down, starting in the middle of the first main tunnel and ending at the bottom with nest chamber. Main entrance is usually closed with soil plug 2-3 cm long in spring and autumn and 8-12 cm long in mid-summer; in early spring and late autumn, many burrows remain open during the day. Emergency exits are dug up to 0.5-1 cm of the ground’s surface. Lengths ofinitial tunnels are 129-275 cm;total lengths of main tunnels are 139-174 cm; and nest chambers are 6-7 cm in diameter for males and non-breeding females, 10-12 cm for breeding females, and 37-51 cm deep. Winter burrows differ from summer burrows by the presence of 1-3 additional (hibernation) chambers, greater depths, and absence of emergency exits; nest cham-bers are 50-130 cm deep; hibernation chambers are 25-50 cm and 70-100 cm deep; and depths of both types of chambers decrease with increases of soil’s hardness. Night shelter burrows are simple, with one tunnel 25-90 cm long, passing from surface with 1-2 right-angled turns to depths of 15-40 cm. One individual in its home range has 2-3 shelter burrows at high density and 5-12 at low density. Entrance of shelter burrow is always open and very visible due to the fan-shaped scatter of earth in front ofit. In the wild, contact between individuals are relatively rare, even in dense populations; frequency of interactions is only 1-2/hour; and individuals often forage 0-5-1 m from one another without any interactions. Among observed interactions, most are neutral, with mutual avoidance after short naso-nasal contact. Aggressive interactions (weakly expressed attacks) are twice as less common as neutral interactions and occur only near burrows.
Status and Conservation. Classified as Least Concern on The IUCN Red List.
Bibliography. Shenbrot et al. (2008), Sokolov et al. (1996), Zhang Yongzu et al. (1997).
description: Published as part of Don E. Wilson, Russell A. Mittermeier & Thomas E. Lacher, Jr, 2017, Dipodidae, pp. 81-100 in Handbook of the Mammals of the World – Volume 7 Rodents II, Barcelona :Lynx Edicions on pages 94-95, DOI: 10.5281/zenodo.6591722