That's interesting Jack. I have cattle and then some goats I can't catch that have access to graze in the spot I planted my unprotected pawpaw several years ago and nothing seems interested in it. Quite surprising they left it alone because the goats seem to clean up anything the cattle don't. The pawpaw seminar I attended by KSU said that deer don't really eat them much or mess with the trees/leaves other than rubbing them at times. Pawpaws can be quite fussy it seems with soil fertility, sun/shade requirements early on in life, sunscald, and perhaps transplant shock with their long taproot. It's hard to say what might have gotten them.