I have never had a problem myself, but over the years I came across a number of rodent problems. Usually in the engine bay which I always put down to the warmth of a cooling engine attracting them. In the boot either behind or in the well of a spare wheel seemed a secondary favourite. I had a cat which I found hiding behind a battery. My wife hand-fed it for a while because it was so young. I assumed it was the runt deliberately left by the mother. Hibernating hedgehogs were reasonably common, and they would burrow into the seat upholstery. It was the rodents that got up inside the dashboards seemed to cause most extensive damage. Seems rats can survive by eating wire insulation, and owners never wanted to go rooting around there with bare hands.