Baffled-What is This?

:) I a 1972 Corvette Coupe and a 1976 "Spirit of 76" Chevy C10.

I do not have a major issue with mice in my trailer. When I first got it I went over the bottom with Flex Seal and closed all the access holes and spaces. Worked great. I got on a creeper and went front to rear. I store it in an out building that does have mice, I also store my vintage cars there. I use small canning jars, filled with moth balls and perforate the lids. Place them in trailer and cars and the mice tend to move on, they do not like moth balls. In a closed area the scent and effect of moth balls is overwhelming. Not just to mice. Effective to bugs and other critters. Poison left me with dead mice I didn't find for months. Snakes are OK, but here in TN you are very likely to get a Copperhead with the Gophers and Kings. They eat too. My cat is reasonably effective with moles but not so much in the crannies and crevices of the shop.

I've tried all kinds of traps. If you only have a few mice traps can work fine but if you have an infestation they just don't seem to kill enough mice quick enough, and the little beasties start to figure it out. The tasty warfarin gets them all right away and they're done. Hungry cats are probably best though. 

There are many new types of mouse traps available from disposable to electrical. They would likely be effective and would not have the risk of a rotting mouse carcass in a hidden place.