Caught a short tailed shrew today in a Victor Tin Cst. It was blind set against a wall, but with a little dab of peanut butter above the doors. PB was uneaten, shrew was alone. Dead in trap, this morning checked trap last night.
Do you suppose it tried to chew out and cut its lips and reacted to it's own poison?

Probably allergic to peanut butter.

Shrews have a high metabolic rate and can quickly die of dehydration, starvation, or other stress. They are probably immune to their own poison.

Stress and the time in the trap with the steel floor I find mice and shrews will expire quickly at times with the right conditions.

I figured they would have to be immune, but there were signs it had chewed the slots in the end alot. I find mice expire quickly when one of the ones caught are hungry. Shrew was probably hungry because most of the mice are gone now.

ah hahahahahahahaha....

Answers #3 and #4 were the right ones.

I catch a good many shrews on PB on a snap trap in my garage.