I breed my own rats, and last week one of my rats had her second litter. Her first litter was 13 normal, healthy babies who all weighed 6g at birth and all made lovely meals for my corn snakes.
However, her second litter contained only two, and there is something odd about one of them. They are a male/female pair, and the male is normal. He probably weighed 6g at birth, but I didn't weigh him until the next day, when he weighed 8g. However his sister, by day two only weighed 4g. Now, at 9 days old, they weigh 20g and 8g respectively. When I check, the little one always has a milk belly, and since there are only two, I don't think her brother is able to shove her out of the way of the milk so I think she's able to nurse as often as she wants to.
The other interesting thing is that while her brother is now fully furred, she has none whatsoever. I know that hairless is a recessive gene, but its still a surprise to have produced one.
Anyway, here is a photo of them at 3 days:
And here is a photo taken yesterday, at 8 days:
As you can see, the little one has no fur (and there's none to the touch either - she still has baby soft skin).
I'm thinking about keeping her just out of interest, but not as a breeder, as from what I've read of dwarfism, they often have fertility problems, and hairless rats often can't lactate, so breeding could be disastrous even if she could produce offspring.
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