Track Mice to Their Entry Point With UV Powder and Peanut Butter

The Problem

Knowing you have mice is easy; knowing where they get in is the hard part — and sealing gaps at random means the one you missed stays in business. Trapping without exclusion is a subscription. What you need is the commute, mapped.

The Technique

1. Pick a spot with rodent sign and set out bait: a good smear of crunchy peanut butter directly beside a patch of UV tracking powder (sold for rodent control — a fluorescent powder they walk through).
2. Leave it two or three days. When the peanut butter's gone, they've been through the powder.
3. Come back after dark with a UV flashlight and follow the glow: powdered footprints run along their travel routes — typically hugging walls — pausing where they pause.
4. Follow the trail to its end. In the video it climbs a wall and disappears into a dryer vent whose flap hangs open behind a lint beard — the entry point, found, not guessed.
5. Seal what you found: exclusion mesh in gaps, a sealing cover on the vent. (Both fixes are their own tips on this site — the excluder-mesh gap fill and the magnetic dryer duct.)