| OCR Text |
Show 318 VULPES, ALOPEX ET VABS. In the Common Fox of North America, we meet with a range of color-variation, irrespective of locality, somewhat akin to that seen in Gam lupus. The prevalent tendency, however, is toward melanism, which tendency is mnch more strongly developed in the colder than in the warmer latitudes. Frequently, individuals of the melauistic type occur in litters of the common variety. The varying degrees of melanism occurring in this species have given rise to several commercial varieties, which have received at the hands of naturalists systematic designations, and been regarded more or less generally as valid species. Generally, these melanistic varieties are more fully furred, with larger and heavier tails*, than the common form. The difference in the fineness and softness of the fur is recognized to such an extent by furriers as to greatly affect the price of the skins, the so- called " Silver v and " Cross " fin* being considered far more valuable than the fulvous type. The so- called " Gross Fox v ( Vulpes " decussatus v) is more or less frequent as far south as Northern New England and Northern New York, and throughout the more elevated portions of the great Rocky Mountain plateau, where it constitutes a large proportion of the representatives of the so- called Vulpes " macrurus". More rarely, the Black or so-called " Silver Fox" ( Vulpes " argentatus") is met with over the same regions, becoming frequent in the higher parts of the Rocky Mountains* and northward. The fulvous form seems, however, to be generally the more prevalent form throughout the range of the species. To the south-ward, it is the form exclusively met with; but near timber- line in the Rocky Mountains, and throughout the ufur countries", it seems to be not much more frequent than the melanistic forms. With this tendency to great variability in color, we meet, as usual in such cases, a great variation in size. In the present case, the variation in color may be properly regarded as geographical, through an increasing tendency to melanism northward. The variation in size is also chiefly of the same character, the size uniformly increasing toward the north, as shown by the subjoined table of measurements. A glance at this i table shows at once the nature of this variation. The largest specimens come from the Aleutian Islands and Alaska: the smallest from Essex County, New York, which is the most southerly locality well represented in the collection. A series of nine skulls from Alaskan localities range in length from 5.70 to 6.20, five out of the nine having a length of 6.00 to 6.20 ( two 6.15 and two 6.20), and give an average of 5.98. In another series of eighteen from the Mackenzie River district ( mainly from Fort Anderson), the range is from 5.55 to 6.10. Only one, however, exceeds 6.00, and three only reach this size, the average being 5.80. These series consist about equally of the so- called " Silver" and common fulvous varieties, and, as may be seen from the table, there is no material difference in size between the two so- called varieties. A third series of nine skulls, of the so- called " macrurus", chiefly from the Upper Missouri country ( including two, however, from the Pacific slope), ranges from 5.40 to 6.00, with an average of 5.75. Two only reach 6.00, and two only fall as low as 5.50. Hence the series forms a third appreciable step in the southward decrease in size. Though the latitude is much less, the elevation of the region is much greater than that of the localities more to the northward. With a similar altitude, the decrease would have been more marked, as is proven by the series * See Bulletin Essex Institute, vol. vi, p. 54. |
