RODENTS OF LIBYA 123 



the Saharan Oases and in the vicinity of the Ahaggar Mountains of 

 southeastern Algeria. 



Owing to the barriers provided by the Gebel es Soda, Gebel el Harug 

 el Asued, and Hamada de Tinrhert, little, if any, outbreeding takes 

 place with populations of G. p. hamadensis to the north and east. The 

 vast Idehan Murzuch and Gebel Ben Ghnema prevent interbreeding 

 with populations of gerbils to the south, so this subspecies has main- 

 tained its genetic identity. 



Members of this subspecies from El Abiad and Temenhint are 

 darker dorsally than those from nearby Sebha. Specimens from the 

 vicinity of Murzuch, Goddua, Traghen, Umm el Araneb, and Meseguin 

 show an orange-colored dorsal pelage. Animals from Ghat in the 

 extreme southwestern portion of the Fezzan are darker and more 

 variegated in dorsal color, with greater admixture of brownish hairs 

 on the shoulders and rump, and have slightly larger skulls with more 

 bulbous auditory bullae. Examples from El Gatrun, which is located 

 a great distance from the type locality at Sebha, possess almost all the 

 characters typical of tarabuli. These specimens, however, are slightly 

 paler in dorsal color and have slightly larger auditory bullae and 

 molariform teeth. Specimens from Brach and Edri in the Wadi es 

 Sciati are more brilliantly colored (Salmon or Orange-Salmon) than 

 any other representatives of this subspecies. 



This local variation in color is demonstrable in all populations of 

 this gerbil throughout the Fezzan. In fact, it appears that these gerbils 

 develop different colored pelage depending upon the type of substrate 

 on and in which they live. This widespread variation is suggestive of a 

 broad genetic constitution, which enables these gerbils to respond 

 readily to the variety of conditions imposed by the prevailing en- 

 vironment. 



An adult female, no. 322196, from El Gatrun is partially albinistic. 

 This specimen is entirely white except for some brownish hairs on the 

 distal portion of the tail and a faint suffusion of brown on the dorsum. 



Ecological observations. These gerbils are the commonest rodents 

 of the Saharan Oases and prefer the sandy areas of the periphery and 

 interior of the oases but also inhabit the vegetated wadis which link 

 the various oases together. They occur sparingly in the margins of the 

 hamadas wherever localized sandy areas are present but apparently 

 do not inhabit the inner portions of these hamadas or the interior of 

 the desolate sand seas. 



Their preferred habitat consists of areas of open sand and the 

 numerous small vegetated dunes near the oases proper. Date palms 

 occur in all Saharan oases, and these gerbils are frequently taken from 



