I bred leucistic black rats many years ago, before they were so popular, and always had a fairly predictable outcome on all offspring. I believe that the rusty is a co-dom mutation, as it always produced (for me) rusties and normals in first gen offspring of rusty to normal pairings. Rusty to rusty would produce rusties, leucistics, and, very rarely, a normal. I believe leucistics to be the super form of the rusty co dom, much as it works in many of the Ball python co doms (see Fire, mojave, etc) This is further supported by leu to leu pairings always yielding only leu offspring and leu to rusty only producing leus and rusties, never any normals.
These are just my observations with 30 or so clutches, if anyone has contradictory findings, I would love to hear your input.

Derek
Cape Fear Reptiles

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