Crepuscular's a term used to describe some animals that're primarily active during twilight, that's at dawn and at dusk. The word's derived from the Latin word crepusculum, meaning "twilight." Within the definition of crepuscular are the terms matutinal (or "matinal") and vespertine, denoting species active in the dawn and dusk respectively. The patterns of activity are thought to be an antipredator adaptation. Many predators forage most intensely at night, while others are active at mid-day an… (More on Crepuscular)