THE INHERITANCE OF THE PLATINUM AND WHITE FACE CHARACTERS IN THE FOX

HE black fox, which is farm bred in the Scandinavian countries, T is descended from animals imported from North America, where it has arisen from the wild red fox through mutation.The mutant gene in the homozygous condition changes the colour of the whole animal, in the same way as a mutation of the agouti gene in the wild type rabbit changes the colour of the whitish underline and the banded guard hairs to solid black.Two phenotypically similar but genetically different mutant types of black foxes are known, viz. the Alaskan and the standard fox.When Alaskan blacks are crossed with reds the F , animals are intermediate in colour, showing the typical ))cross fox)! character, but the standard black x red foxes produces a smoky red fox, where the colour of the red fox is strongly, but not completely, dominant.Crosses between Alaskan and standard foxes produce ))blended cross foxes)) with characters from both of the first mentioned hybrids.The genetics of these crosses is explained by WARWICK ant1 HANSON (ASLIBROOK, 1937) as follows: AABB red fox, aaBB Alaskan black fox, AAbb standard fox, aABB cross fox, AABb smoky red liybrids, AuBb blended cross foxes, etc. Breeding data seem to fit in very well with this hypothesis.The modern silver f o x is a product of selection from the Original, almost wholly black, mutants.The silvering is caused by an intermingling of light banded guard hairs among the black hairs.The wild red fox has such silver hairs in varying numbers, particularly 011 the rump and loin, and some silver hairs are found even on the most genuine black foxes.The silvering is a quantilative character which is present in both red and black foxes, but the black fox and its mutants, e.g.white face and platinum, which will be discussed later, are qualitatively different from one another and from the red fox,The common red fox, which ranges over the northern parts oT -PLATINU,M AND WHITE FACE CHARACTERS -~~~ hnerica, Europe and Asia, ought to be considered as belonging to one and the same species, Vulpes vulpes L., as pointed out by COLE and SHACKELFORD (1943).Local varieties or breeds can easily be distinguished, but, owing to the fact that all these varieties freely interbreed as soon as opportunity offers, there seems to be no logical reason to speak of different species.Mutant black foxes have also appeared from time to time among the wild living Scandinavian red foxes, and some of these mutants have been kept in captivity long before any importations of North American silver foxes were made.Such mutants have not been utilized, however, to build up any strains of our present day fami foxes.Sometimes the breeders may use Scandinavian red foxes for crossing with the farm-raised silver foxes, and in this way some of the local ~)viilpes blood)) may find its way into the breeding stock.The Scandinavian silver fox breeding is, however, almost exclusively founded on imported animals, viz. the Canadian standard silver fox, probably due to the fact that skilled fox farming with selection for high quality pelts and extensive silvering started much earlier in North America than in the Scandinavian countries.In Canada and Northern U. S. wild living black foxes and their cross products with the red fox seem to be of rather frequent occurrence, but in Sweden they are exceptional.BUTLER (1845) has studied the data on more than 700.000Canadian fox pelts of the Hudson's Bay Company fur returns 1915-1944.He found the highest percentage of silver fox pelts in British Columbia (8,o % silver and 41,s % hybrid3) and the lowest in Saskatchewan (3,o % silver and 2 4 , ~ % hybrids).The frequency of silver foxes has decreased during the last 30 years.from about 9 to 3 per cent.Three possible explanations of this decrease are put forward, viz.migration, differential survival or reproductive rates, and changed classification standards.WARWICK and HANSON'S factorial hypothesis fitted well to the observed frequencies of the different colour phases.

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