Also, I'm sure that many(if not most) of the joeys that are born with defects are cannabalized before they come OOP because mother gliders(like most animal mothers) know when there's something wrong.
Because of that there are probably alot of issues that we don't know about. To make matters worse, joeys that are rejected are then hand-fed and sold to be breeders. Thus passing on whatever may be wrong with them. :\
I know this is a bit off topic, but IMO, handfed joeys should ONLY be sold to pet-only homes since there could be something wrong with them that cause momma to reject them in the first place.