The survival threshold for pinky possums is 19g; if they weigh less than that, no amount of effort will save them. The rehab manuals advise euthanasia for any baby possum under 19g. When I learned that as a newly-minted rehabber nearly two decades ago, I was sure it had to be wrong; I learned from painful firsthand experience it’s correct.
So he showed up with the nine teeny-tinies, and I knew just looking at them they were under the survival weight threshold. But I weighed every one, to be 100% sure, and their weights ranged from 6-7g—well under the survival threshold. I humanely euthanized them, and yes, it hurt like hell. Euthanizing babies is always the worst; they’ve had no chance at life.