diurnal animals are active __________.
These terms describe when an animal is most active: 1  Nocturnal - active primarily at night. 2  Diurnal - active primarily during the day. 3  Crepuscular - active primarily during both dawn and dusk. Many animals that are casually referred to as nocturnal are actually crepuscular.  Metaturnal - active part of the day and part of the night.