As an animal behavior, nocturnality describes sleeping during the daytime and being active at night - the opposite of the diurnal human lifestyle, and that of those animals with which we're most familiar. The intermediate crepuscular schedule (twilight activity) is also common. Some species are active both during the day and night. Living at night can be seen as a form of niche differentiation, where a species' niche is partitioned not by resources but by time itself, for example temporal divis… (More on Nocturnality)