Crepuscular animals are those that are active primarily during
twilight (i.e., the period before
dawn and that after
dusk). It is thus to be distinguished from
diurnal and
nocturnal behavior where an animal is active during the hours of daylight or the hours of darkness respectively. The term is not precise however as some crepuscular animals may also be active on a moonlit night or during an overcast day. The term
matutinal is used for animals that are only active before dawn, and
vespertine for those only active after sunset.