mumma mouse secluding 1 baby??

Question
hello Tamarah, My Mumma mouse had her first litter on sunday (10 born, 2 stillborn). She is a funny little mouse who does not like being picked stil but loves company and loves sitting at the bars of the cage fpr as long as i stand there, she is a sweet little character who is easy to placate as long as you give her food to munch on. so in this case she was happy, calm and distracted and did not seem at all fussed that i peeked at her bubbas to count them. (we have a crittertrail cage where you can simply pull the nesting box off with out disturbing mymma and putting your hands in). i did not touch bubbas and used a spoon to scoop out the 2 little ones that dod not make it. she had also separated 2 other bubbas as i dont think she waas able to get the tissue off them (it was stuck to them from the blood/liquids from the birth. they were seriously stuck! so i with out ouching them put small amount of water from my nail on the tissue to disolve it off. a while after popping the nesting box back, we noticed that one baby was down out of the nest. we were not sure if mumma was trying to get baby back in the nest or not. it was like she was trying to do something with it, as she kept picking him up, put putting down again and again. it was almost like she didnt know how to get him up into the box(its not actually that high...). next day (today, being thursday), i took babies out to see them (being day 3 or 4 and reading that this is the time to start handling them) and realised there were only 7 there. so searched the cage and found one hidden under some material cloth i gave her for her nest. it was luckily still alive but very cold, so i poppd him back in the nest. why is she doing this? is it possible that the baby has been attatched to the nipple when she was leaving the nest and been pulled out and she cant get them bAck in (which seems too weird), or that she is purposely sepating the baby? i just want to constantly keep counting them to make sure now.....

Answer
Hi Liz,

Either is a possibility, but it would be a good idea to continue to check the cage and nest and replace any lost little ones until they get they get big enough to handle themselves.  Little ones can be mischievous and crawl out of the nest on their own or be dragged out while nursing like you mentioned.  If mom is separating him on purpose it could be that she doesn't feel like she has enough milk for the size of her litter, so she's kicking one out.  She could also sense that something might be wrong with him, or he could smell off for some reason.  It will probably be less of a problem once his coat comes in, so just keep popping him back in the nest until then.  You might want to give mom a bit of kitten milk replacement (you can dust some over her food, or use it as a milk substitute and make her a mouse-sized portion of scrambled eggs with it) and perhaps some dry cat kibble to help her produce enough milk to feed that many pups.  8-10 is a good litter size, but for some moms, it can be hard to keep up with that many babies!

Best of luck, and let me know if you have any more questions!
-Tam