Bunnelby spend much of their time with their large, shovel-shaped ears pressed against the ground, for they spend their time digging enormously large burrows, and even when away from home will often dig to uproot immobile plants and grass pokemon for food. This process places their remarkably sensitive ears in frequent contact with the earth, and they are therefore able to sense the planet's vibrations from long distances away.
Historically, these vibrations were caused primarily by impending earthquakes, and humans followed the Bunnelby's warnings to evacuate; although some of the earthquakes which disturbed these pokemon were too small and weak to seriously harm human structures, enough were dangerous that listening to the Bunnelby was a worthwhile way to prevent tragedy. Bunnelby in this period were imported to several active fault zones, although others such as Kanto refused them, for they posed a major threat to the local flora's root systems. Today, listening to the Bunnelby will still protect people from earthquakes, but evacuating one's home or place of business every time they bounce wildly through town is a far more frustrating task. Human construction and demolition work today often involves loud equipment which shakes the Earth enough to disturb the Bunnelby, and while a single town may know to ignore them, these vibrations often carry too far for even emergency warning personnel to be aware of every potential source. And humanity has proved unwilling to calm down enough to avoid disturbing these pokemon.
It is believed that biological evolution will eventually solve this problem, for this process is already underway. Bunnelby today at times ignore modest vibrations, such as from construction equipment, for they are far too common; in time, the Bunnelby will again provide a reliable warning, but this gives little solace to the victims of present seismic tragedies.