Crepuscular describes animals that are most active during twilight: the dim periods at dawn and dusk when the sun is below the horizon but light still fills the sky.

Many animals prefer these in-between times because it's cool enough to move around comfortably but still light enough to see. Rabbits are crepuscular, hopping out to feed in the early morning and evening shadows. Deer emerge from the woods at dusk to graze in fields. House cats, descended from crepuscular wildcats, often get their famous “zoomies” right around sunrise or sunset.

Being crepuscular offers advantages: these twilight hunters and foragers avoid the hot midday sun and the complete darkness of midnight. They can see better than daytime predators in dim light, but they're harder for daytime predators to spot than animals active at noon.

When you're camping and notice more animal sounds and movements right as the sun sets, you're hearing the crepuscular creatures beginning their active hours. If you want to spot wildlife, dawn and dusk are often your best times, because that's when crepuscular animals are on the move.