LÖNNBERG, MAMMALS FROM BRIT. E. AFRICA. 21 



Wroughton's subspecies appears also to differ in colour 

 as he describes its colour as »'Mars-brown' ticked with whit- 

 ish». This indicates a reddisb tone^ in the brown which 

 is entirely absent in tbe specimens from Donya Sabuk. The 

 oldest specimen with somewhat worn fur comes nearest to 

 »Prouts brown», the others are as already described grizzled 

 with buffish and blackish brown. The face of P. h. hindei 

 is said to be like the back, »but the obsolescence of the 

 pale tips of the hairs between the eyes making it darker».^ 

 Any such obsolescensce of the pale tips of the hairs on the 

 forehead is not apparent in this series, and only in one or 

 two of the youngest the interorbital area is somewhat, but 

 not much, darker than the back. 



Although from a geographical point of view tbe Rock- 

 rabbit of Donya Sabuk could be suspected to be Procavia 

 brucei hindei, we thus find that it differs from the descrip- 

 tion of that subspecies in several respects as well with re- 

 gard to colour as to skull measurements. It is, however, a 

 well known fact to every one who bas studied these animals, 

 that they display a considerable amount of variation so that 

 it often is very difficult to decide with full certainty to 

 which race and even »species» a specimen ought to be re- 

 ferred. Since I have bad, some years ago, the opportunity 

 of studying the conditions of life of these animals in East 

 Africa, I think that I understand the cause of this varia- 

 tion to some degree. This variation bas its origin in isola- 

 tion and I will endeavour to explain this as follows. Very 

 often such rocky formations which constitute the home of 

 a colony of Hyraxes are situated in a great distance from 

 each other, and the intervening stretches of country, whether 

 steppe or thornbush, are far too broad to be crossed by the 

 Hyraxes with any degree of safety, or are perhaps even 

 quite unsurpassable. An exchange of individuals between 

 the different colonies is in many cases thus, if not impos- 

 sible, so at least very difficult and very scarce. Sexual inter- 

 course between the colonies does not take place, or very 

 seldom. In fact it may often happen that these colonies 

 are fully as isolated as if they were situated on different 



^ Perhaps this has something to do with the red soil at the type 

 locality Fort Hall? 



2 Ann. Mag. Nat. Hist. (8) Vol. 5. 1910, p. 107—108. 



