Xena had been the runt of the litter of 11 and had been attacked by her siblings, which was why the litter was split up (which is how I happened to have Fudge, Curly, Greta and Blackie). So today, Ashley decided Xena was doing well enough to return to some of the litter and gave her to me. (I named her Xena, because I figure she was kind of a "warrior princess.") I tried working her in with the others, but ultimately I could see that it was not going to be good for Xena and I told Ashley to come and pick her back up again. But I kept this record of what it was like.
It's obviously "survival of the fittest" even in the puppy world.