Salpingotus crassicauda Vinogradov 1924

3.

Thick-tailed Pygmy Jerboa

Salpingotus crassicauda

French: Gerboise a queue grasse / German: Dickschwanz-Dreizehenzwergspringmaus / Spanish: Jerbo pigmeo de cola gruesa

Other common names: Dzungarian Thick-tailed Pygmy Jerboa (crassicauda), Gobi Thick-tailed Pygmy Jerboa (gobicus)

Taxonomy. Salpingotus crassicauda “/inogradov, 1924,

Shara-Sumé, N Xin iang, China.

Salpingotus crassicauda is in the subgenus Anguistodontus. Two subspecies recognized.

Subspecies and Distribution.

S.c.crassicaudaVinogradov,1924—EKazakhstan(LakeZaysanBasin),NWChina(NXinjiang),andSWMongolia.

S. c. gobicus Sokolov & Shenbrot, 1988 — S & SE Mongolia and N China (N Gansu and W Inner Mongolia [= Nei Mongol]).

Descriptive notes. Head-body 47-62 mm, tail 91-117 mm, ear 8-14 mm, hindfoot 20-27 mm; weight 6-14 g. The Thick-tailed Pygmy Jerboais very small, with no significant secondary sexual dimorphism. Condylo-basal lengths of skulls are 15-4-17-7 mm, mastoid breadths are 14-3-17-3 mm, and maxillary tooth row lengths are 2:9-3-6 mm. Head and dorsum are ocherous gray, with scattered dark gray; sides and ventral pelage are pure white. Tail is fatty, with short gray terminal tuft; fat deposits in tail are greatest in the anterior one-third and gradually become thinner toward tip. Hindfeet have three toes, covered below with brushes of white hairs; conic calluses at bases of toes are absent. Ears are short and tubiform. Auditory bullae are greatly inflated and strongly project from under braincase laterally and caudally. Mastoid cavity is large and completely subdivided into three sections by septum. In volume, mastoid cavity is about twice as large as than tympanic cavity. Front surfaces of incisors are yellow. P' is present and slightly smaller in diameter than M?. Molars are low-crowned, with tuberculous surfaces; crown heights of unworn molars are ¢.80% of their lengths. Glans penis is small, thin, elongated cone-shaped, and not subdivided into lobes; its surface 1s naked. Os penis (baculum) is rudimentary and rachis-like; its length is about equal to one-tenth of the length of glans penis. Chromosomal complement has 2n = 46 and FN = 92.

Habitat. Sand and sandy-gravel plains in semi-desert and desert zones, with grass (Poaceae)sagebrush (Artemisia arenaria, Asteraceae) vegetation.

Food and Feeding. Diets of Thick-tailed Pygmy Jerboas mainly contain seeds; insects are minor (15-30%) components of diets.

Breeding. Pregnant Thick-tailed Pygmy Jerboas were recorded in eastern Kazakhstan in May-July and Mongolia in June-August. Females produce two litters per year. Litters have 1-6 young, usually 2—4. Gestation (by indirect estimates) lasts 19-20 or 25 days. Sexual maturity occurs at 9-11 months of age.

Activity patterns. The Thick-tailed PygmyJerboa is strongly nocturnal. Activity has two periods: 2-4 hours in the first one-half of the night and 1-1-5 hours in the second. Hibernation starts in September and ends in the end of April.

Movements, Home range and Social organization. Summer home ranges of Thicktailed PygmyJerboas are 0-3-0-5 ha, with no sexual differences in size. In spring, home ranges of males increase to 1-5-1-8 ha. Social interactions are mainly agonistic, usually with pursuit terminating by direct fighting. Summer burrows of males have 1-3 entrances and one nest chamber 5-7 cm in diameter at depths of 15-25 cm. Burrows of breeding females have up to six entrances, one nest chamber 7-8 cm in diameter at depths of 10-33 cm, and 1-5 additional chambers.

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

Bibliography. Shenbrot et al. (2008), Sokolov et al. (1996), Zhang Yongzu etal. (1997).