Garbage Eater

Journal entry
Amorphous glob seemingly inhabiting trash cans. Curious habitat! Cans seem to provide defenses; creatures pop head(?) up to spit up projectiles. Definitely magical in nature - possibly from proximity to academy? Or does trash itself host faint magic props? What happens when food runs out? Do they find new cans? No indication of mobility... maybe they roll? (no - this is dumb idea)