FYI, both mice & rats with eyes still closed require very little oxygen to stay alive...I suspect this is a survival adaptation, since the moms have such big
litters & sometimes the babies are set aside without being cleaned up (w/o the afterbirth & membranes removed) when they are born too fast. They can
appear dead & blue for quite some time & still be revived...I know because I breed rodents & have cleaned up & then given "CPR" to forgotten pinkies to
maximize litters. It's amazing since mouse pinkies are so tiny- I literally do rapid chest compressions with my fingertip & it usually works.