Of all the monitor collective nouns, “gathering” points most directly at the one scenario reliably known to pull normally solitary monitors together: a carcass. Komodo dragons, the largest and most famous monitor species, are well documented gathering at a single kill, sometimes a dozen or more individuals drawn in by scent from remarkable distances, using a keen sense of smell that can detect carrion from miles away.
These gatherings are tense rather than cooperative. Size determines the pecking order, larger, older Komodo dragons feed first and can be aggressive toward smaller rivals competing for the same meal, and fights over carcasses do occur. It’s one of the more dramatic examples of reptile social behavior precisely because it looks so unlike the quiet, spaced-out lives monitors otherwise lead.
Smaller monitor species show milder versions of the same pattern, temporarily tolerating each other’s company wherever food is unusually concentrated.
Example: “A gathering of monitors had converged on the carcass by late afternoon, each one keeping a wary distance from the others.”
Related: Collective Nouns for Reptiles · What Is a Group of Monitors Called?