104.

Tarabul Gerbil

Gerbillus tarabuli

French

: Gerbille de Lybie / German: Tarabul-Rennmaus / Spanish: Gerbillo de Tarabul

Other common names: Libyan Gerbil, Riggenbach's Gerbil

Taxonomy. Gerbillus pyramidum tarabuli Thomas, 1902,

Sebha, Libya.

Gerbillus tarabuli was earlier considered a subspecies of G. pyramidum, with which it shares some morphological characters, but D. M. Lay in 1983 suggested that it merits treatment as a full species on chromosomal and morphological grounds. Further revisions of various geographical forms in Tibesti (Chad) and desert areas, combined with cytogenetic studies, have supported the present constitution, distribution and speciesstatus of G. tarabuli, as outlined by G. G. Musser and M. D. Carleton in 2005. Molecular work by A. Abiadh and colleagues in 2010 found G. latastei as sister taxon of G. tarabuli, but those authors did not include G. pyramidum in their analyses. A. Ndiaye and team in 2014 found G. tarabuli from Morocco to be closer to G. occiduus and distant from G. henleyi, which was also confirmed by V. Nicolas and colleagues in 2014. Monotypic.

Distribution. Sahelian savannas and desert areas from S Morocco, Western Sahara, Mauritania, and N Senegal E through Algeria, S Tunisia, Mali (N of Niger River), and Niger to C Libya and NW Chad.

Descriptive notes. Head-body 84-117 mm, tail 107-155 mm, ear 12-16-5 mm, hindfoot 25-31 mm; weight 19-46 g. Significant sexual dimorphism exists in head-body length and hindfoot length, with females smaller than males. The Tarabul Gerbil is a medium-sized gerbil with sandy to orange-brown dorsal pelage and white venter. Preorbital, supraorbital and post-auricular white spots are visible, and forefeet and hindfeet are white, with hairy soles. Long tail (120-145% of head-body length) ends in marked pencil of dark hairs. Females bear four pairs of mammae. Chromosomal complement has 2n = 40, FNa = 74.

Habitat. The Tarabul Gerbil may live in various types of habitats in Sahelian savannas. In Mali and Nigerit is found in sandy zones with Acacia or Prosopis africana (both Fabaceae). In Mauritania it iscommon in fixed dunes and sandy silt soils with Capparis (Capparaceae) trees and Panicum (Poaceae) bush. It can be found also in any sandy substrate, including those in close proximity to human settlements.

Food and Feeding. The Tarabul Gerbil is probably granivorous, but no real study ofits diet has been made.

Breeding. Main breeding season of The Tarabul Gerbil in Mauritania was seen to be April-November, during wet season. Pregnant females may have 3-6 embryos in Mauritania and 2-6 in Mali-Niger (average 4-1).

Activity patterns. The Tarabul Gerbil is nocturnal and terrestrial. It digs shallow (15— 25 cm beneath surface) but complex burrows, with openings plugged during daytime.

Movements, Home range and Social organization. The Tarabul Gerbil is probably less mobile than other gerbils. Maximum recapture distance in four days varied between 7-5 m and 30 m. Tarabul Gerbils are able to return to burrows even if released at 1000 m or 200 m, respectively, in 69% and 40% ofcases.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Tarabul Gerbil arrived recently in Senegal, which was interpreted as result of increasingly arid climate and Sahara extension.

Bibliography. Abiadh, Chétoui et al. (2010), Abiadh, Colangelo et al. (2010), Granjon & Dobigny (2003), Granjon & Duplantier (2009), Granjon etal. (1999), Lay (1983), Musser & Carleton (2005), Ndiaye et al. (2014), Nicolas, Ndiaye et al. (2014).