My small storage shed where I keep my lawn tractor has become a home for a large family of mice. So far I have caught 4. My lawn tractor is <10 years old and it may have soy-based insulation on the wires. So far the wires are intact. When I worked for Bayer as a research chemist one of the projects I worked on was to find a more environment friendly oil to replace petroleum oils in polyols. We found that soy oil worked well. Back then I had no idea that soy-based wire insulation maybe a treat for rodents.
Here's an article I found on it: Does Your Car Have Wiring That Rodents Think Is Tasty?
Here's an article I found on it: Does Your Car Have Wiring That Rodents Think Is Tasty?