Is Mice damage covered on car insurance?

It depends on what type of insurance you have and what the damage is.

Some insurance companies have a storage plan which basically fall under Comprehensive. Since mice can eat your headliner, your wiring, plastics, etc. it really depends on how bad and severe the damage is. They may not cover something like mice eating a headliner, but if they damage the cars wiring system and it consequentially doesnt allow your car to start, than the insurance company could very well cover the costs of the harness or any parts that may have been damaged due to the rodents. Like if the wiring shorted out the ECM (engine control module) due to rodents eating the wiring and the wiring touching when you started the car.

Your best bet is to call your insurance company to find out the particular details of your coverage.