I used to shoot the pricks off the top of my water heater in me old place years back with my TEX 086 pellet pistol. After sealing the entry routes, I switched over to smooth peanut butter with finely powdered Alka Seltzer mixed in. The rodents would end up dead & bloated out like tennis balls with legs & a few of 'em actually burst from the internal gas pressure generated by the reaction of the Alka Seltzer with the rodents stomach acid. Rats & mice don't vomit or burp, so the gas has only one way out which is usually filled with poo pellets. T'was fun to hear the fooks pop under the trailer at night.