Couple of posts here talk about soy based insulation being why rodents chew wires up....believe me they've been eatin wires long before any soy was introduced.
Back in my early days of phone tech life, the learning process starts with pullin cable. The outer jacket of the common cables in use then (3, 25, 50, and 100 pair) was PVC...Polyvinyl Chloride....mice, squirrels, and rats just loved this stuff. When we ran into damaged cables we replaced them with the more expensive 'fire rated' cables and problem solved. These locations were usually under construction trailers and in outdoor areas like lumber yards and garden centers. Been chased by some big ass rats with attitude in DC. (Once you weren't the new guy anymore, you got to send the new 'new guy' under the trailer.)
My last issue with wires being chewed was in my driveway on my Ford Focus....squirrels chewed threw a wire harness feeding the injectors on top of the motor...pile of acorn debris next to it, so I guess the insulation was dessert. Dang squirrels are just rats with fuzzy tails!
+1 on mothballs