First published in Mouse Fancy Review, April 1984.
The Puzzling Pearl
The Pearl is a lovely, delicate colour, but I have found it a most reluctant breeder, and while the bucks seem normally fertile the does are frequently barren, or have litters that often fail to thrive after weaning. Also, a Pearl which goes beyond three months without blotchy moult marks is a rarity with me. In fact, I had just about decided to abandon Pearls altogether when I made some progress by using a Chinchilla as an experimental cross. A Chinchilla doe put to an Agouti buck produced litter of Agouti Tans, and when I put these back to Pearls I didn’t really know what to expect. What I did get was a wide range of colours: Agoutis, normal and blue, plus self blacks, blues, chocolates and Pearls. The selfs may turn out to be silvered, as they are not yet in adult coat.
The Pearls are very varied: two are very dark on top but drift white at base (and very attractive). One is a nice acceptably-standard Pearl, and two have a sort of yellow dusting over the fur in the tan distribution area—might they be primitive Pearl Tans?
With this interesting development my enthusiasm has been rekindled, and I am eagerly waiting for the young does to be put back to a Pearl buck. I can’t begin to predict what the next results will be! The babies are all healthy and vigorous, though somewhat nervous, as my Pearls are wont to be. I shall soon find out if the peculiar Pearl coat quality will be retained in the adult coat, and whether they will breed true.
As a last thought, none of the young ones—over 40 altogether from four does—had pink eyes. I wonder what would happen if I introduced the pink eye dilution factor to pearls?
Footnote by Roger Hutchings
I have been test-mating Pearls for nearly two years past. I began on the assumption that they resulted from the combination of Chinchilla and Silver Grey (as stated way back by Elsie Blowers, who standardised them in 1935), but extracted neither from them. Crossing with Chinchilla gave primitive Agoutis (as reported above by Ruth Hollis), which when mated back to Pearls provided a proportion of more or less standard Pearls. When crossed with Silver Grey there was no intermediate stage of silvering in subsequent generations. Crossing with true-breeding self Black produced a third generation of blacks, blues, chocolates, lilacs and Pearls (but no silvered, and none of the selfs developed silvering).
At this stage I must presume that the gene involved produces a similar (and virtually indistinguishable) effect whether its background is self or agouti pattern, and whether black, blue, chocolate or lilac. The investigation continues!