RODENTS OF LIBYA 171 



dorsal color. Two specimens from near Nalut, 321833 and 321834, 

 are the darkest dorsally of any of the Libyan populations of this 

 subspecies and have more orange on the dorsal surface of the tail. 

 Specimens from Derg, 321842, and Mizda, 321862, are noticeably 

 paler dorsally than other representatives of this subspecies. 



Judging from the morphological homogeneity within and between 

 the various populations, these jirds must interbreed freely throughout 

 their range in Tripolitania. The vast expanses of the Hamada el 

 Hamra and the rugged escarpments of the Gebel Nefusa have proved 

 ineffective as deterrents to dispersal of this subspecies. To the north- 

 east, however, the more humid coastal areas apparently provide 

 unsuitable habitats, and to the south, the Hamada de Tinrhert and 

 Gebel es Soda have retarded or entirely prevented gene exchange with 

 the Fezzanese populations. Specimens are not available from localities 

 between the ranges of M. c. caudatus and M. c. conjalonierii to the 

 northeast and M. c. ampins to the south; however, when specimens 

 do become available from these areas, they probably will show 

 intergradation between M. c. caudatus and these contiguous subspecies. 



Ecological observations. These jirds are unknown from localities 

 outside Tripolitania but have disjunct distribution throughout the 

 hamadas and oases of the interior. Then- range includes the inner 

 portions of the broad coastal plain of northwestern Tripolitania. The 

 climate and terrain here are not unlike those of the inland deserts 

 and generally are not typical of the coastal plain. 



In Tripolitania, representatives of this subspecies were collected 

 from a wide variety of habitats as follows: Nalut: Localized, vegetated 

 dunes supporting Calligonum and bushy, thorny perennials. Numerous 

 burrows were present throughout the trapline, most of which were 

 probably made by gerbils. Mizda : Occasional mounds and hard eleva- 

 tions in the bottom of a badly eroded wadi. The vegetative cover con- 

 sisted primarily of two species of thornbush growing among the 

 hummocks. Bir Allagh: An isolated concentration of sandy-clay 

 hillocks supporting thornbush in the midst of otherwise barren 

 hamada. Derg: Margins and bottom of a shallow wadi with occasional 

 hillocks of sand interspersed with denuded rock-strewn areas. Most of 

 the trap settings were made near the entrances of active burrows. 

 Hun: Large, localized permanent mounds supporting almost impene- 

 trable growths of a thorny perennial in the midst of an extensive 

 sandy plain. 



These rodents are normally nocturnal, but near Hun, a subadult 

 specimen was caught in full daylight only a few seconds following 

 the setting of the trap. 



At the various collecting sites in Libya, they occurred with Meriones 

 libycus; Gerbilius aureus; Jaculus jaculus; Gerbillus campestris; Jaculus 



