My momma gerbil

Question
She had babies and there 4 weeks old last Friday so another expert told me that when they are 4 weeks I could seperate the boy's from the girls so I put the 4 boys with there dad and the only girl with her mom.So the mom looks like she may be getting big again so I don't know if she is pregnant or not.I saw where it said that she could get pregnant right after she gave birth to her last litter but she would carry the new ones  until the others were weaned from her.Is that true?What do I need to look for to tell if she's pregnant again?

Answer
Hi Stacey.

There are generally very few signs of pregnancy in hamsters and gerbils until the very last stages, in which the female will seem to gain weight rapidly, especially toward the hind end.

It is very true that gerbils (and hamsters) can get pregnant again within minutes of giving birth to a litter, so if you removed the male any time after the birth of your last litter, then your safest bet is to assume that she is pregnant again and to start preparing for another litter.

It is not true that the female will carry the pups until she has weaned the first litter; what is true is that nature has made it so that the period from birth until weaning of pups and the gestation period (the time that the female is pregnant for) is almost the exact same period of time, so that she will have finished weaning her first litter by the time she gives birth to the second.  Convenient, no?  This is why rodents are such productive little animals, as far as having babies go.  

Thanks for the question, feel free to ask me any others you may have!