Pygeretmus platyurus

23.

Lesser Fat-tailed Jerboa

Pygeretmus platyurus

French: Petite Gerboise / German: Kleine Fettschwanzspringmaus / Spanish: Jerbo de cola grasa pequeno

Taxonomy. Dipus platurus Lichtenstein, 1823,

Kuvan-Darya River, Kyzylorda Region, Kazakhstan.

Pygeretmus platyurus is in the subgenus Pygeretmus. Monotypic.

Distribution. W, C & E Kazakhstan, NW Turkmenistan (Balkhan Region), and NW Uzbekistan (Karakalpakstan).

Descriptive notes. Head-body 75-115 mm, tail 70-95 mm, ear 18-25 mm, hindfoot 30-36 mm; weight 19-69 g. Female Lesser Fat-tailed Jerboas are slightly larger than males. Condylo-basal lengths of skulls are 20-8-24-3 mm, zygomatic breadths are 16:6-21-1 mm, and maxillary tooth row lengths are 4-1-5-1 mm. Head and dorsum are dark, dim clayish gray; sides and ventral pelage are light yellowish gray; and tail is short and fatty, with short black terminal tuft. Toes of hindfeet are naked from below; 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. Molars are high-crowned, with terraced masticatory surfaces; crown heights of unworn molars are 125-165% oftheir lengths. Glans penis is lanceolate, flattened, 3-8-4-5 mm long and 2-2-4 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 7-8 longitudinal rows, with 12-14 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 and low saltwort vegetation on clay soils.

Food and Feeding. The Lesser Fat-tailed Jerboa is very folivorous, eating mainly leaves and stems of succulent plants. Seeds and underground plant parts are only eaten in small amounts.

Breeding. Breeding of the Lesser Fat-tailed Jerboa occurs in April-June, with peak intensity from end of April to mid-May. Litters have 2-8 young (average range 5-3-5-7). Overwintering females produce one litter per year. Sexual maturity occurs at 10-11 months of age, after overwintering.

Activity patterns. The Lesser Fat-tailed Jerboa is nocturnal. Aboveground activity usually starts 30-35 minutes after sunset and ends immediately before sunrise. Hibernation lasts from October to mid-April.

Movements, Home range and Social organization. Main type of locomotion of the Lesser Fat-tailed Jerboa is asynchronous ricochet jumps. Maximum length ofjump is 54 cm. Maximum running speed is 5-3 m/s. Escape behavioris characterized by hiding on the ground’s surface. Individuals usually stay within 70-100 m radii of their permanent burrows. Summer burrows are simple and consist of the main tunnel, starting from the main entrance and ending at the bottom with nest chamber; several (1-3) additional chambers are placed along the main tunnel; and in rare cases (¢.5%), burrow has one additional tunnelstarting from the first additional chamber and leading to emergency exits. Main entrance usually is closed with soil plug, but in spring, some burrows remain open during the day. Lengths of main tunnels are 70-200 cm (usually 100-130 cm); nest chamberis 6-9 cm in diameter for males and non-breeding females and 13-18 cm for breeding females; and nest chambers are 15-50 cm deep, usually 35 cm. Winter burrows differ from summer burrows by an additional 3-5 hibernation chambers, greater lengths (240-360 cm, usually 300 cm) and depths (115-150 cm, usually 130 cm), and a steeper main tunnel. The Lesser Fat-tailed Jerboa does not build night shelter burrows.

Status and Conservation. Classified as Least Concern on The IUCN Red List.

Bibliography. Shenbrot et al. (2008).