436 Dr. E. Lonnberg on the 



JjYIH.— On the Variation of the Weasel (Putorius nivalis, 

 Linn.). By Dr. EiNAR Lonnberg. 



In the ' Annals ' for January last, Mr. G. E. H. Barrett- 

 Hamilton communicated an interesting " Note on the Weasel, 

 Putorius {Ictis) nivalis, Linn., and some of its Subspecies," 

 in which he seems inclined to subdivide the species in 

 question into a number of " subspecies." I do not dispute 

 the fact that some of these may be found to be valid and 

 distinct enough to deserve subspecific rank, but 1 believe 

 this can hardly be the case with all of them. Of course, 

 the idea as to the meaning of a subspecies varies somewhat 

 with different authors. I suppose, however, that even in 

 a subspecies the distinguishing characteristics (although 

 tliey are of less importance than specific ones) must be 

 constant to a certain degree and inherited from one genera- 

 tion to another ; in the opposite case it is only an indi- 

 vidual variety. Such independent individual varieties must 

 not be called subspecies, in my opinion, even if they are 

 numerous and dominate in some region. In his intro- 

 duction jMr. Barrett-Hamilton says : " In the far north, as 

 is well known, the weasel regularly turns white in winter, 

 and this character is in itself sufficient to warrant the sub- 

 specific separation of those individuals whose winter coat is 

 white from those which, as in England, do not undergo 

 such a seasonal change of colour." I am not inclined to 

 accept this statement under present circumstances for reasons 

 given below. 



Mr. Barrett-Hamilton recognizes as the first " subspecies " 

 '^Putorius nivalis typicus^ Linneeus : type locality, Upsala, 

 Sweden " ; and the second is '^ Putorius nivalis vulgaris, Erx- 

 leben : type locality, Leipzig." The difference between these 

 subspecies appears to be that the former turns white in winter, 

 the latter does not. If any sharp geographical boundary- 

 lines could be drawn between these forms, the probability for 

 their separation would increase. Such, however, is not the 

 case. In the northern and middle parts of Sweden the 

 weasel regularly turns \vhite in winter. In Scania, the 

 most southern province, on the other hand, all weasels are 

 brown during the winter. This has already been pointed 

 out by Sven Nilsson in his various memoirs on Swedish 

 mammals, but he says he does not know the northern 

 limit of those weasels which are brown in winter. Later 

 authors, as, for instance, Lilljeborg, do not add anything to 

 our knowledge on this subject. According to the literature, 



