Shrew-mouse problem

I live in a stack rock foundation home that is quite rural, with a dirt and bedrock crawl space. There is an open area beside the water heater with small openings to the crawl space below for pipes and wires. I saw a small grey ball of fur dash from there into the bathroom, I set up a mousetrap and soon killed a shrew. I have since been studying up on them, and have caught several more, as well as several mice. Further, something has either eaten on the spot, or pulled out of the mousetrap and removed, one dead mouse and one dead shrew before I could get to emptying the trap. This was on successive days, and then another entire mousetrap and dead shrew disappeared, but I could heard the sound of something trying to eat or remove it from where it had been dragged out of my sight behind the inaccessible water heater tank for hours that morning. My questions are these – why are shrews in my house – they eat bugs and mice. What is eating the dead animals from the traps? If there are shrews, which prey on mice, why are there mice? Thanks for your kind consideration – I have had a camera set up since the mousetrap was stolen, but nothing has stolen any dead animals since. I think whatever it is has had its fill. Please help with this mystery. Shelly, Ontario.

Shrews are carnivores, They will eat just about anything that they can overpower, including each other. I would not be surprised to find that shrews were responsible for at least some of the ‘missing’ trapped animals. As to what else might be involved, I hesitate to guess. In addition to the camera set-up, I suggest using white flour or a similar powdery substance dusted around the traps and on the floor in the vicinity of the water heater tank to see if an tracks appear that then may be identified.