EPA vehicle biodegradability…
EPA vehicle biodegradability requirements led to use of soybean-based wiring insulation. Manufacturors were stuck between a rock (being barred from sales in US) and a hard place (selling vehicles that might fall apart, going down the road)--the "least bad" option was moving from petroleum based wiring insulation, to insulation made from something that is food, to rodents.
If you want images, search "vehicle wiring rodent". There are hundreds of images.