Mice...they don,t like the smell of dryer sheets(Downy sheets)I put them everywhere in my car..
#1 is above sun visors(saves headliner)
under seats
up under dash
scatter a few inside car
couple in the trunk
under hood I wrap some around plug wires and at the electrical block at firewall.
This has worked great for me since learning about dryer sheets 5 yrs ago.Aslo springtime fresh at first spring startup.:D