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The blue fox is a color phase of the Arctic white fox and may occur anywhere in the range of the typical animal. In fact, the blue phase bears the same relationship to the white that the black phase does to the red fox. In the Pribilof, or Fur Seal, Islands of Alaska, however, through the influence of favorable climatic conditions, assisted by artificial selection in weeding out white animals, the blue phase has become the resident form. Isolation on these islands has developed other characters also which, with the prevailing color, render the Pribilof animal a distinct geographic race of the white species. A blue fox is also the prevailing resident animal in Iceland.

In years when fur-seals were killed in considerable numbers on the Pribilofs their carcasses remained on the killing grounds as a never-failing store of food through the winter. During summer there is an abundance of nesting water-fowl, and throughout the year there are mice on land and the products of the sea along shore. As a result the foxes have thrived amazingly and several hundred skins have been produced a year. With the lessening number of seals now being killed on the islands and the resulting scarcity of winter food, the fate of the foxes is somewhat in doubt. The Pribilof skins are of high market value, bringing from $40 to $150 each in the London market.

Stock from the Pribilofs has been introduced on a number of the Aleutians and other Alaskan islands for fur-farming purposes. The value of these fur-bearers is so great that special effort should be made not only to keep up the stock on the islands, but still further to improve it.

The Pribilof foxes have from five to eleven young, which are usually born above ground and are later carried to the shelter of dens dug in the open or under the shelter of a rock. Foxes have become so accustomed to people on these islands that they have little fear and come about boldly to satisfy their curiosity or to seek for food. They often show an amusing interest in the doings of any one who invades the more remote parts of their domain. White animals born on the islands or coming in by chance when the pack ice touches there in winter are killed, whenever possible, in order to hold the blue strain true.