322 THE WILDERNESS OF THE UPPER YUKON 



and that the existing variations are the result of the grad- 

 ual extension of the ranges of sheep of the two extreme 

 types of color, with consequent interbreeding. At least, 

 even if the different colors of sheep are caused by their 

 environment, interbreeding must still be a factor in pro- 

 ducing such irregular variations. 



CARIBOU 



Two well-marked species of caribou in Yukon Ter- 

 ritory have been determined the Barren Ground, Rangi- 

 jer arcticus, and the woodland, so-called Rangifer os- 

 borni. At present there is not sufficient material in our ' 

 public institutions to define accurately the exact relation 

 between these two types and the other named species of 

 caribou in British Columbia and Alaska. The life-history 

 of no other large animal in the north is so difficult to 

 observe as that of the caribou, and it would require special 

 investigations extending over several years to determine 

 accurately their distribution and habits. 



The caribou in the Ogilvie Rockies is the true Barren 

 Ground type. It is smaller in body and skull than the 

 woodland type, its horns are less diverging and lighter in 

 beam, although many of the horns of both types have 

 characters so identical that the resemblance is complete. 

 The only difference in the habits of the two types con- 

 sists in the Barren Ground caribou's tendency to wander 

 more restlessly over a wider area, and especially in its 

 banding together in the fall and migrating. In Yukon 

 Territory its habits are similar to those of its neighbor 

 in the Barren Grounds of Canada, except in so far as the 



