1388 



YEARBOOK, 1937 



This demonstrates how quickly the majority of farmers produced 

 the maximum of light-silver pelts. Some cautious breeders, however, 

 are retaining some of the darker silvers in the breeding herd as an 

 insurance reserve, in case there should be a sudden return to the half 

 and three-quarters silvers, which are more satisfactory for scarf 

 purposes. Other breeders feel confident that the genetic make-up of 

 silvering is dependent upon so many factors that persistent selective 

 mating toward darker colors would supply such a new demand just 

 as effectively, though perhaps somewhat more slowly. They feel that 

 their method permits maximum concentration on full silvers for the 

 present higher prices. There are no authentic scientific data available 

 to demonstrate that either method is correct, and thus the producers 

 continue to be faced with an important problem that for the present 

 remains unsolved. 



RESEARCH IN INHERITANCE IN THE FOX 



It is quite generally appreciated that there is still much room for 

 improvement in the color and texture of silver fox fur. The pelts now 

 coming to the market are generally somewhat better in quality than 

 a year ago, but this is true mostly for individual ranches rather than 

 for sections of the country. Since the number of pelts offered for sale 

 is increasing year after year, buyers are naturally becoming more 

 discriminating, especially with the increased competition that now 

 involves other countries as well as the United States. Fox farmers have 

 reached the point where they must exert every possible effort to im- 

 prove the quality of the fur produced. For the present, close culling 

 of the breeding stock, which means pelting the undesirables, and in- 

 telligent and strict selection of breeding animals are the most certain 

 methods to bring about a marked improvement in fur quality. 



To meet the need for fundamental information on the genetic basis 

 of silvering, the Biological Survey began an experiment in 1935 at the 

 United States Fur Animal Experiment Station, at Saratoga Springs, 

 N. Y. An attempt is being made to determine, if possible, the genetic 

 factors involved, so that market requirements can be met more 

 promptly. The objective is to determine the relationships between 

 the various degrees of silvering and to work out methods of breeding 

 that will enable the breeder to have more control over them. Only a 

 small number of foxes is available for this experiment, whereas ex- 

 perience proves that a large number must be used to obtain definite 

 results where many genes are concerned. There has been only one 

 other research program to trace the inheritance of fur colors, and this 

 was concerned not with gradations in silvering but with the basic 

 differences between red, cross, and black (silver) foxes. To make this 

 clear, it is necessary to give a brief account of these different types. 



Before the development of fox farming, there apparently occurred 

 in the common red fox (Vulpes fulva) two distinctly different mutations 

 to black. One of these, namely, that to which the standard or Prince 

 Edward Island silver fox traces its origin, must have occurred some- 

 where in Canada, probably in the eastern or central part. The other, 

 to which the Alaskan silver fox traces its ancestry, certainly must have 

 occurred in Alaska, most likely in the interior. The so-called cross 

 fox was probably produced by crossing the red and the silver (fig. 5). 



