Wowser! What weirdness! I've heard about them, but never cnsidered them a problem in my urban home. Where do you guys all live? Looks like mostly northern states... Are moles and shrews a northern problem? A rural problem? I never heard of anyone here having problems. (Houston)
Oh, and please do NOT EVER use caster beans. They are beautiful trees, and I once snitched a few seedlings from a neighbor's place. They grew quite tall (for small, not-really trees), and were a lovely purple color. But... they drop those large white seeds everywhere. I have turtles in the yard, and one was within the drop-range of the castor beans. He was a valuable and rare tortoise, friendly and with quite a personality and vitality. He ate a seed, apparently, and died a slow and miserable death. With turtles / tortoises, their metablolsms are so slow that you don't really know something is wrong until it's really wrong, and the poison had entirely immersed itself in his system, beyond help. All I noticed was that he was slowing down in his activity, eating less, lethargic, and generally miserable. But, that can just mean warm weather has him sleepy. I was wrong. He died a slow and horrible death, from slow poisoning. KEEP AWAY!