that is a strange one as the main circuit from batt to SR/SR to starter/SR to bulkhead are large wires & I wouldn't think a rodent would chew thru something that large but I dont know animals so I am speculating & if it chewed thru & severed a wire then that hot end would have to fall down & make contact with ground to effect a dead short. I'm thinking more a mechanical shift of something that grounded. However my new therapy cat that I adopted from CL, within a week it chewed thru the ph cord (a real thin one) & the next day it was relocated to the Humane Society.