168 U.S. NATIONAL MUSEUM BULLETIN 2 75 



In the Fezzan, these large rodents are known from comparatively 

 few localities. No specimens are available from northern and western 

 Fezzan, although suitable habitat is widespread, particularly in the 

 vicinity of the oases of Sebha, Temenhint, Brach, Edri, El Abiad, 

 Ubari, and Ghat. Future collecting in these areas, however, will 

 probably reveal the presence of these jirds. 



The specimens available at present are almost indistinguishable 

 morphologically, which suggests a free interchange of genes within 

 and between populations in the eastern Fezzan. Two distinct color 

 phases, a dark and a light phase, are present among the specimens 

 from Meseguin and El Gatrun; some are intermediate in color. Animals 

 representing all these color types are indistinguishable, however, in 

 cranial characters. Therefore these wide ranges of color types suggest 

 a variable genotype for color and do not indicate basic genetic differ- 

 ences. At present, specimens are too few in number and are from too 

 few localities to allow any generalizations about the full extent of 

 variation among the various populations in the Fezzan. 



These jirds from the Fezzan are clearly not closely related to any 

 other subspecies of M. caudatus in Libya and probably have closer 

 affinities with populations in southern Algeria, Niger, or the northern 

 Chad. 



Ecological observations. These jirds apparently require loose 

 sand for their burrows. At all collecting sites, areas of pure sand or 

 small dunes formed the dominant habitats, and specimens were never 

 taken in areas devoid of sand. At the type locality at El Gatrun, a 

 good series was obtained from the small dunes and sandy areas inter- 

 spersed among the date palms. Frequently, these large rodents were 

 caught in traps set upon sandy elevations having a dense cover of 

 young palms. Usually in these habitats, large burrows are visible 

 beneath the palms. The collecting sites near Murzuch, Traghen, and 

 Mesequin were all characterized by areas of loose sand associated 

 with densely growing, bushlike date palms. 



Apparently they do not occur in the marginal areas of the oases 

 where areas of loose sand and date palms usually are lacking. These 

 marginal habitats are typically hamada-like, and if vegetation is 

 present, it consists of Tamarix and Calligonum growing upon isolated 

 clay hummocks or sporadic growths of small, succulent plants inter- 

 spersed on barren playas. 



In areas of loose sand, tracks and pathways of these jirds are wide- 

 spread and usually extensive complexes of burrows are present. On 

 several occasions, specimens were taken from traps set within or near 

 entrances to burrows. Only rarely were traps holding full adults found 

 in position in the trapline. Generally they were found dead several 

 feet distant from the nearest trap, apparently after having been fatally 

 struck. 



