This happened to my Bolt twice, in the fall of 2017 and spring of 2018. Both times they got into the front bumper area and started eating the wiring harness. The first time I took it in the service manager knew immediately that it was rodent damage by the way - that ought to tell you something.
Both times I was fortunate that my insurance company covered the damage. I spoke with my insurer (AAA) at length about the issue. They are tracking the issue on multiple makes of cars. While mice have nested in cars for a hundred years, the problem has increased significantly in some cars recently, including the Bolt. Its about the design of the car, probably the fact that there are less petroleum odors, but primarily in their opinion because Chevrolet has shifted to new wiring insulation on some vehicles like the Bolt away from traditional petrochemical wiring insulation to a new eco friendly soybean derived wiring insulation. AAA has seen this as a real issue and is tracking it as of 2018.
The second time it happened I did take permanent steps to try to solve the problem. That time I asked then to thoroughly wash out the area to remove any mouse/urine odors that might make it smell like home, and I supplied an aluminum tape to the dealer and they wrapped it around the new wiring harness before they installed it. I also purchased an item off Amazon - search for:
Fanhome Under Hood Rodent Repellent Animal Repeller
Go ahead and roll your eyes, it sounds like junk, but - this unit uses high pitched audio that my kids can hear from 25 feet away from the car with the hood closed that chirps and squeaks and has some small leads that flash under the hood. Apparently it turns off when the car is in motion.
Maybe it was the tape, maybe the rodent repeller, both, or just luck, but since the spring of 2018 the under hood unit is still working and nothing has chewed on my wiring since then. My advice would be to install the unit for $30, which is a lot less than $600 for the repair.
I appreciate that I could spray peppermint or set traps or build a flaming moat around the driveway, but so far the solutions I've tried are working for me...