ALLELES: i+ (wild-type), i (mutant).
PHENOTYPE: Coat color is an off-white. Individual hairs are largely devoid of pigment, but small masses of sepia material or occasional granules occur in the proximal portion. The agouti band and tip of hair are completely devoid of pigment. Older deer mice are lighter in color than the young. Animals- superficially resemble albinos. Ivory animals gave a greater ability to oxidize tyrosine and dihydroxyphenylalamine than do albino deer mice.
Eyes are red in color, but darker than in albino.
INTERACTIONS: Probably epistatic to all other known pelage color mutants, except albino. Crosses between albino (c/c) stocks and ivory (i/i) on an otherwise P.m. bairdii background invariably yield "wild-type" offspring, a striking example of complementary gene action in mammals.
SOURCE: About 1937. A single male P.m. rubidus, wild-trapped near Eugene OR, showed the trait.
REFERENCE: Huestis (1938), Clark (1938), Foster and Barto (1963).