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Show 313 With these general remarks, we will pass now to a more special examination of geographical variation in size in several of the more common species of the North American Ferce, based on the abundant material in the National Museum. CANIS LUPUS. The common Gray Wolf of the northern hemisphere presents a range of individual variation in color exceeded by but few known species of Mammals; gray, white, and black individuals, with various intermediate stages of coloration, occurring with greater or less frequency wherever the species abounds, several of these varieties sometimes occurring in the same litter. Black and white wolves seem to occur more frequently at some localities than others, but gray is generally nearly everywhere the prevailing color. Cream- colored and rufous varieties are also said to have a wide prevalence over some parts of the great plains of the interior. To what extent these variations in color are to be considered as geographic is not yet well established.* With such an evident tendency to variability, it is not surprising that geographical variation in size is displayed in this species to a marked degree. The variation in this respect constitutes a pretty uniform decrease in size southward, as shown ( see the subjoined table) by the size of the skull, only fully adult skulls being here taken. The largest are from Fort Simpson and other localities in or near'the Mackenzie River district, six of which, out of a series of nine specimens, exceed 10.25 inches in length ( one reaching 11.50!), and the other three average above 9.50, the whole averaging 10.38. The next in size are from the region about Puget Sound, a series of three ( the only ones in the collection), averaging nearly 10.50. Of sixteen specimens from Forts Benton, Union, and Randall, on the Upper Missouri, the average is 9.45, the extremes being 10.50 and 8.50. Nine specimens from Forts Kearney and Harker ( chiefly from Fort Kearney, and all pretty old) average a little larger than the Upper Missouri specimens, the extremes being 10.15 and 9.35. A single specimen from the mountains of New Mexico reaches 10.00, while the three most southern ( from the Rio Grande and Sonora, Mexico) average only 8.37, being the smallest of the whole series, and averaging 2.00 shorter than the series of nine from the Mackenzie River region. This < lifference is fully 25 per cent of the average size of a series of upward of eighty specimens; while the difference between the smallest ( from Saltillo, Mexico) and the largest ( from Fort Simpson) is 3.75, or nearly 40 per cent, of the average size of the whole series! * See further on color variation in this species. Ball. Mus. Comp. Zool., vol. i, pp. K"> 4- 158. |
