Few rat questions, mostly about pregnancy

Question
QUESTION: I have a female and a male rat, Princess and Dopey, they dont live together but we do let them play for a bit each day. We had intended on getting a female for ours,(we didnt know they were suppose to be kept in pairs) but the guy we got him from only had him left, so thats what he brought over.
We got Princess last sept or oct, and Dopey only about 2 months ago, Im guessing he was a monthish old.
We want her to have one litter, so we can keep a male and a couple females, but she hasnt had any pups yet. Lately though my bf has mentioned she has been acting 'different', shes normally friendly and that hasnt really changed, but she seems calmer and more cautious. And just now when she was standing up on her bars I noticed I can see her nipples just slightly. I heard the whole heat thing, but when I touch her hind she doesnt do anything, just sits there. Could she be pregnant? If so, how far along could she be, based on those few signs?

I was also wondering what colours they may be. Princess is a red eyed, (i think) dumbo eared, siamese or himalayan, and Dopey is a dumbo eared, black hooded, with black eyes.

Lastly, my bfs brother has Dopeys sister, supposedly from the same litter, but she is so tiny and he is just massive. Miss Bojangles(the sister) is pretty much the same size as when he got her, but Dopey easily doubled in the same time. Is that normal?

Thanks for any help, when I asked this on Yahoo Answers everyone just yelled at me for breeding instead of adopting, even though I told them I searched.

And if I already sent the same question Im sorry, computer issues.

ANSWER: It's pretty normal for males to be ginormous compared to their sisters - they're just big in some lines.
Has she started nesting, and do you see a considerable bulge to her tummy? She may be picking little squabbles with the male or throwing a fit when things interrupt her sanctuary of a corner or house. Sometimes, you don't realize they're pregnant until they surprise you with babies. Either way, have another cage ready and separate Princess from Dopey the instant she litters. Dopey can and probably will re-breed her and you'll end up with back to back litters. Not healthy, not good!

It's hard to base what babies may look like given that you don't know the history of the parents (as in what they came from, etc.).. if your siamese is black based you could end up with siamese, black berkshires, hooded, variegated, or any other plethora of markings. If she's agouti based, you'll probably end up with agouti babies in those markings (and Siamese, of course, if he carries it). They both could carry markings and colors you have no idea about, either. Kind of a crap shoot.


Good luck.

---------- FOLLOW-UP ----------

QUESTION: She sleeps alot in her hut, but Im not sure if shes nesting. She was playing with paper earlier and it ended up in her bed, same with a piece of fabric from her hammock. Is that considered nesting? We use shavings in their cages, should that be removed and replaced with newspaper or something(i heard somewhere that should be ok)? And they arent in the same cage, but they are beside eachother. How about picking her up? Should we leave her in her cage until we know for sure?

How do you know if shes agouti or black based? Do you just have to know her background? We got her from a petstore and all the rats in the cage were the same as her(if that helps any). Im just excited and hope they dont all look the same.

Thanks again.

Answer
Yeah, that's usually some signs of nesting.. some rats nest without being pregnant, though; so just keep an eye on her. Aspen is fine in their cages, as long as you don't use pine or cedar you're fine, and your doe can have a litter on shavings just fine. I prefer it over newspaper - cleaner, no ink on the babies to be absorbed through the skin.

There's no way to tell just looking at a Siamese/Himalayan if they're black or agouti based - it depends on what pops up in your litter, and the genetic history is helpful. Just think of it as an easter egg hunt. :)