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Fat Sand Rat

Psammomys obesus

French: Psammomys obese / German: Fette Sandratte / Spanish: Gerbillo de arena grueso

Taxonomy. Psammomys obesus Cretzschmar, 1828,

Alexandria, Egypt.

The chromosomal complement of P. obesus was described by A. G. Smith and colleagues in 1966, and the karyotype ofJordan specimens was given by M. B. Qumsiyeh and D. A. Schlitter in 1991. Four specimens recovered in Port Sudan, on Red Sea coast, by H. W. Setzer in 1956 complete the previous specimens recorded (as “ P. elegans ”) from same region by M. T. von Heuglin in 1877. D. L. Harrison and P. J. J. Bates in

1991 considered all Arabian specimens to belong to subspecies dianae. Three subspecies recognized.

Subspecies and Distribution.

P.o.obesusCretzschmar,1828—NAfrica,fromMorocco,WesternSahara,andMauritaniaEtoEgypt,Sinai,Israel,Palestine,Syria,JordanStoCArabianPenisula.Pralo.zonesdianaeofSaudiMorrison-ScottArabia.,1939—Elitto-P. o. elegans Heuglin, 1877 — NE Sudan.

Descriptive notes. Head—body 116-185 mm, tail 88-140 mm, ear 13-17 mm, hindfoot 32-36 mm; weight 82-237 g. Males are slightly larger than females, but sexual dimorphism was nottested. A large gerbil-like rodent, the FatSand Rat is characterized by a long pelage colored in ocher to tawny brown that is more or less dark regionally, and a short tail (around 70% of head-body length) terminating in a black pencil. Flanks and ventral pelage are lighter than dorsum, becoming pale ocher. There is a small white post-auricular patch. Soles of hindfeet are partially hairy, and claws are dark. Skull is massive, and inflated tympanic bullae represent ¢.32% of maximum length of skull. Upper incisors do not show any grooves. Females bear four pairs of mammae. Standard chromosomal complement has 2n = 48, FN = 74-78.

Habitat. The Fat Sand Rat prefers halophytic steppes (seasonally flooded “dayas” or salt flats “sebkhas”) with compact muddy and salty sandy soil (salinity 9-30 g/1) where they can find essential succulent bushy chenopod plants. Some colonies have been found in rocky regions in Jordan and in low sand mounds around Anabasis (Amaranthaceae) shrubs in Sinai.

Food and Feeding. Fat Sand Rats eat only leaves and stems of Amaranthaceae (Arthrocnemum, Atriplex, Halocnemum, Salsola, and Suaeda), which are succulent (90% water), and recycle the salty water and oxalic acids that the plants contain. The diet is augmented by seeds in October, before rainy season, and by fruits in winter (principally February). During estivation, Fat Sand Rats have a low rate of water-recycling.

Breeding. Gestation period is 24 days, and average littersize is 4-8 (2-8)with seasonal variation (3-6 in September, 6 in winter January-March). Young weigh 6-7 g at birth, are weaned after 15 days, become adult at 120 days, and reach sexual maturity in 3-6 months. Sexual activity of females is correlated with rainfall and rain days, which can cause delay of up to one month; male activity is not dependent on weather conditions.

Activity patterns. The Fat Sand Rat is both diurnal and nocturnal, and is terrestrial. Peak of activity is observed from 09:00 h to 17:00 h in winter, but only early morning and late afternoon in summer. They frequently sun-bathe early in morning. These rodents can build very complex and extensive burrows up to 1 m below soil surface and with different levels of tunnels. Each burrow system, with many entrances sited below bushes, corresponds to a colony and the tunnels are connected by different galleries to nest and storage chambers. A large layer of vegetable matter is present on the floor of the nests.

Movements, Home range and Social organization. Fat Sand Rats live in colonies in which females have smaller home ranges than males (average 76 m against 160 m). Range of male overlaps those of several different females. They move regularly from one part of home range to another, 10-30 m from burrow entrance, to gather food and bring it home. They are relatively solitary, and adult males are aggressive toward juvenile males. They communicate through sonic and ultrasonic squeals and footdrumming, and mark their territory with urine and feces.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Fat Sand Rat may be locally very abundant, with up to 42 ind/ha in some parts ofits range, but major fluctuations in population size have been recorded. It may store large quantities of barley in its burrows. Considered a pest for agriculture and human health.

Bibliography. Aulagnier et al. (2009), Corbet (1978), Daly & Daly (1973, 1974, 1975b), Fichet-Calvet (2013b), Fichet-Calvet, Jomaa, Giraudoux & Ashford (1999), Granjon & Duplantier (2009), Harrison & Bates (1991), von Heuglin (1877), Petter (1961c), Qumsiyeh & Schlitter (1991), Shkolnik & Borut (1969), Setzer (1956), Smith et al. (1966).