I've lived in the woods for 20 years and only since getting my first Camry in 2007 have I had this problem. (Well, a mouse did make a nest in a lawn mower engine once.) In the past three years I have had rodents chew through windshield washer wires and hoses, turn signal and headlight wires, and turn my cabin air filter into their personal larder for storing hands-full of nuts and dry dog food. Now they've figured out a way to get into the cabin of the car and I can't figure out how/where. I would love to block their entrance because I am still trying to get the smell of dead rat out of the car after finally relenting and using a block of poison under the front seat (the rat ended up dying in the back seat during a day that hit about 95 degrees). This rat couldn't have squeezed through an air vent - it wasn't a little field mouse, it was the size of a Coke can not counting the tail. But in one weekend of not driving she had set up a home, stolen hand lotion, kleenex, 3/4 of a can coozie (chewed into small pieces - I found a few), and I guess was building a nest (although I've never found all that blue can coozie foam).