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Black Torts and Black-Yellows

Part 2 of 2

Author: Grant Forrest

From Issue 28 Jan 1999

In the Autumn issue part 1 of 2 I described the interaction between the non-agouti/black (a) and sex-linked yellow (To) genes to produce Black-Yellow and Black-Tortoiseshell colours. I would like to take this a stage further and describe the combination of black, yellow and a white patterning gene to produce a tri- coloured hamster. Before doing so, I'd like to correct an error in the article in the last issue. In the table illustrating a cross between a black-yellow male and a black female, the lower right cell should read aa to/Y, not aa To/Y.

Tricolours are not a new variety. Tortoiseshell and white is a tricolour, consisting of golden, yellow and white areas, but the distinction between the yellow and golden areas is not as striking as the contrast between the black and yellow of a black tortoiseshell. The choice of white patterning gene to use to produce a tricolour is a matter of personal preference. Both Banded (Ba-) and Dominant Spot (Dsds) will do the trick. I prefer the effect of Banded, as it produces a solid area of white rather than variable white spotting. The choice of long or short hair is also up to the individual breeder - I don't think there are any convincing reasons for choosing one over the other. There is really no secret to producing tricolours. I'm sure many breeders will have their own preferred method but rather than list them all, I will describe my method which is to cross a black-yellow male with a black banded female:

black tort 2

On a good day, one would expect every fourth pup to be a tri-coloured female. In practice, if you get one tricolour you're doing well. You might expect that crossing a tricolour back to the black-yellow father would improve the chances of tricolours. Unfortunately it reduces them to 1 in 8. If your black banded mother is homozygous for the banded gene (BaBa) then this method averages 50% tricolour females and 50% black banded males. At present, there is no method of distinguishing a pure banded from a banded carrier, but the method works in either case. If you are uncertain about how to produce a black-yellow male, see part 1 of this article in the Autumn issue. But it doesn't end here! The coloured patches on a tricolour can be modified by several other genes. There are too many permutations for an exhaustive list, so I'll just mention two combinations briefly. The addition of rust (b) will dilute the black areas to chocolate, giving a mixture of white, chocolate and yellow with brown ticking. Cinnamon (p) dilutes the black to a pale dove grey, giving a mixture of white, honey and dove grey. Neither of these colours are standard, but black tortoiseshells may be shown under the new standard for tortoiseshell, whilst black tricolours could (at least in theory!) be shown as patterned. I've never put this last case to the test, but I'm interested to hear from anyone who has.