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Mongolian Jird

Meriones unguiculatus

French: Mérione de Mongolie / German: Mongolische Rennratte / Spanish: Gerbillo de Mongolia

Other common names: Clawed Jird, Mongolian Gerbil

Taxonomy. Gerbillus unguiculatus Milne-Edwards, 1867,

Eul-che-san hao (= Ershi san hao), 16 km north-east of Tschang-Kur, northern Shanxi, China.

Initially considered a member of genus Gerbillus, M. unguiculatus was them removed to Pallasiomys and later attributed to Meriones . It was reviewed by G. M. Allen in 1940, G. B. Corbet in 1978, and I. Ya. Pavlinov and colleagues in 1990 on basis of morphological traits. Some authors described also a peculiar phallic morphology and contrasted it with M. meridianus and Rhombomys opimus . R. Gamperl and G. Vistorin in 1984 provided the most detailed karyotype for this species and its variability. Molecular analysis by M. Ito and team in 2010 found M. unguiculatus to be a monophyletic clade and sister to M. meridianus . Monotypic.

Distribution. Russia (SE Siberia, including Transbaikalia), C & E Mongolia, and NC & NE China (Gansu, Inner Mongolia [= Nei Mongol], Ningxia, N Shaanxi, N Shanxi, Hebei, and Liaoning).

Descriptive notes. Head—body 97-132 mm, tail 85-106 mm, ear 13-15 mm, hindfoot 24-32 mm; weight 52-60 g. The Mongolian Jird is very similar externally and in size to Midday Jird ( M. meridianus), but has a tail shorter (70-90%) than head-body length. Dorsal pelage is grayish brown, while ventral one is dull white (gray with white tips), which differentiates it from all other Chinese gerbils. Tail is bicolored and ends in a black tuft of hairs. Soles of hindfeet are fully hairy. Tympanic bullae are large, and their mastoid parts project far behind occipital condyles. Karyotype 2n = 44.

Habitat. Semi-deserts, sandy steppes, and grassland habitats. The Mongolian Jird is adapted to survive hard frosts in winter, but is never found in mountain zones.

Food and Feeding. The Mongolian Jird is mostly herbivorous, taking seeds and green matter and fruits of desert plants.

Breeding. In Inner Mongolia, reproduction was observed in natural enclosures for four years. Reproduction and recruitment occurred in March—-August and stopped in autumn, and significant seasonality in population density was evident. Similar observations were made in agricultural croplands at samelatitudes and in desert environments. In captivity, Mongolian Jirds are monogamous, and multiparous females may chase and fight young males and even kill them. It has been reported that old females, when they lost their mate, did not accept another one, and polygamous mating groups are less successful than monogamous pairs. Males are sexually active at around 35-45 days of age, while active spermatogenesis and mating behaviorstarts at ¢.70-84 days. With females, the vagina opens at 40-76 days and they are able to reproduce at ¢.63-84 days. High precipitation and temperature both affected the demography or delayed reproduction. After gestation of 19-30 days, averagelitter size is 4-7 young (record 12) and weaning occurs at 20-30 days.

Activity patterns. The Mongolian Jird is nocturnal and terrestrial, digging burrows. It inhabits steppe and semi-desert environments of Mongolia, where the continental climate alternates hot summers and cold winters, with temperatures ranging from +40°C to =35°C and mean rainfall of ¢.350 mm. E. Scheibler and colleagues studied its burrow architecture in the wild, and in 2006 described typical burrow as having 2-8 entrance holes connected to underground system of 2-23 tunnels of 3-4 cm diameter. These authors distinguished three types of burrow: summer, winter, and temporary. The longest and largest were the winter burrows, which reached maximum average depth of 63 cm (against 41 cm and 27-5 cm for summer and temporary ones, respectively). Temporary burrows have no chamber and a low number of entrances. Winter burrows have nest chamber at 57-5 cm and feeding chamber at 25-6 cm on average; these are below the level of permafrost, and it has been suggested that the animals keep warm by gathering together in large numbers in a nest. Summer burrows do not have a feeding chamber, and nest chamber is situated at depth of ¢.25 cm in the soil. Nest chambers contained grass clumps, as well as rubbish and waste from nearby city. In feeding chamber the jirds stored green parts or seeds of various local plants.

Movements, Home range and Social organization. The Mongolian Jird survives 3—4 months in the wild, but in captivity females may produce young at up to 20 months and reach two years of age. It lives in groups of 2-17 individuals; study of each social group showed that home ranges were slightly larger during breeding season (average 309 m?) than in non-breeding periods (average 263 m?), with low rate of overlap (0-17-7%). Males were in general more mobile than females. Mongolian Jirds live in groups ofvariable size that correspond to extended family groups; young of the year stay in parental burrows for first winter. Each social unit is composed of males and females and has its own cluster of burrows, which constitute main activity zone for the clan. In this zone, group-members have priority access to food and chase off intruders. Neutral zones (relative overlapping zones) of 1-4 m wide occur in the contact zones between groups. All members of a clan cooperate equally in caching of food in winter stores. Larger males are most active in territorial defense. During breeding season, the marking rate increases in reproductively active males and estrous females. A female may copulate with more than one male (promiscuous mating).

Status and Conservation. Classified as Least Concern on The IUCN Red List. Classified as a pest species, the Mongolian Jird is also sold commercially in the pet trade and is used for medical research (with laboratory colonies). Despite some threats linked to increase in livestock grazing that may have adverse impact on its natural grassland habitats, the species is abundant.

Bibliography. Allen (1940), Agren et al. (1989a, 1989b),Bannikov (1954), Cohen (1970), Corbet (1978), Gamperl & Vistorin (1984), Gromov (1981), Gulotta (1971), Ito et al. (2010), Liu Weiet al. (2007), Norris & Adams (1972b), Pavlinov et al. (1990), Scheibler et al. (2006), Smith & Yan Xie (2008), Wang Gang & Zhong Weifeng (2006), Wang Yue et al. (2011), Weiss et al. (1970), Xia Wuping et al. (1982).