Need some quick advice- first litter born this morning

So Wendy finally had her litter this morning. Ive peeked in and boy its a big one. Im positive theres atleast 12 babies, but at times am counting as many as 16 (hard to tell for sure without invading her space). She made 2 nests, and is being an awesome mommy... Except for one. Shes left that one in the other nest all alone. Ive seen her go check on it, its very much alive, and shes let it feed atleast once that Ive seen (her cage is covered with a towel except for my peering in every few hours). I feel like shes rejecting it, which I know happens... But heres the part where Im confused... It is -by far- the largest of the litter. It looks like its a day or 2 older than the others (though I know it isnt). I understand rejecting a runt or unhealthy baby, but this one is neither (so far). I worry about it keeping its body temp up, not eating enough, etc. I am going to cull the litter down to 5 or 6 most likely, but I just feel a sense of urgency with saving that one in particular. I really dont know why. Should I let it all play out, should I remove that one and put it with another female (Ive heard that even females that havent had a litter will lactate if there are babies, can someone confirm/deny?), should I try putting it in the other nest? Im so torn here. At one point she had taken another baby out of the big nest, and I had no interest in "playing god" with that one. But this one... I just feel like I need to do something. I know, realistically, its probably best to leave it alone... Thoughts?

Females who have not been bred will not lactate in time to save an abandoned pup. While nursing can induce lactation, it is sadly not a fast enough response to save a starving pup.

Wendy may have abandoned your giant pup deliberately, but if she's feeding him, I highly doubt it. She may be protecting her other babies from having to fight for milk. She may also be splitting her nest so that predators find one but not both. It's pretty hard to read the minds of tiny little mus musculus. It doesn't help that they're not always entirely logical. Once you cull down, place them all together, and she should be fine.

I'd be really impressed if she figured out the biggest baby and moved it away from the others. I can't advise you as I haven't been in this situation but I'd be inclined to leave it be, particularly if she is visiting and feeding. I completely understand your wish to intervene though.

Congratulations on the first litter!

I went to the pet store and came.back, she moved (or ate) him, I dont see him. And shes put a much smaller baby over there... Im not sure theres much rhyme or reason to her actoons at this point. Shes ocassionally scattering them and then bringing them back together, it seems. I guess well see over the next few days.

My guinea pigs sometimes had really really big babies and they died soon after birth. Maybe something was genetically wrong and she could sense it. Mother nature does things sometimes that seem weird or unfair, but there always seems to be a reason. Good luck with you litter.

Well when I went to bed last night, all the babies (including the big one) were alive and well. She moved about 4 babies over to the small nest, and was going back and forth between the nests. I tried to peak in before I left for work, but it was still dark and I didnt want to bug her. Ill know more at about 1 pm (pacific time)

So no one got eaten? Good! I'd be tempted to cull sooner rather than later if even she's aware of how many babies there are.

So I was able to hold babies today (: There are 14 happy, healthy babies. None have died so far. The super big one has slowed down a little and has become closer to the size of his(?) litter mates, but is still the largest. She has now split the litter pretty much down the middle with 2 nests right next to each other. I will be culling in the next few days, unfortunately. Im a bit torn up about it, I thought my first time culling would only be having to get rid of a few... I have to get rid of more than half the litter. But I want to be able to see markings, as well as be certain about whether Im grabbing a male or female. For now she seems to be managing surprisingly well. All the babies are fed frequently and attended to. But I know culling is for the best, and needs to happen as soon as possible.