You must have come across several lists of diurnal and nocturnal animals, but do you know how these animals differ from each other? Many people will be quick to point out that diurnal animals are active during the daytime, while their nocturnal counterparts are active at night. The differences between them though, go well beyond just this fact.
Diurnal or Nocturnal … or Both?
Some species are diurnal in winter, but switch to nocturnal behavior in summer. The subterranean mole rat (Spalax ehrenbergi) is an apt example of the same.
All species on the planet have evolved to make the most of all available niches, which is why some species are at their active best during the daytime, while others are active at night. Animals that are active (or plants that bloom) during the daytime are considered diurnal, while those that are active at night are considered nocturnal.
Besides these, there also exist crepuscular animals (active during twilight, i.e., at dawn or dusk) and cathemeral animals (active during the daytime as well as at night, depending on external factors).
Diurnal Vs. Nocturnal Animals and Plants
▶ The foremost point of difference between diurnal and nocturnal animals revolves around the time of the day when they are active (and the time they spend resting in their dwelling). Diurnal animals are active during the daytime, and sleep at night. In contrast, nocturnal animals are active at night, but spend the daytime sleeping.
▶ The list of diurnal animals includes squirrels, elephants, gorillas, various birds of prey, insects like butterflies and bees, and even humans. On the other hand, the nocturnal animals’ list is dominated by bats, owls, lemurs, flying squirrels, ocelot, moths, tarsiers, etc.
▶ Most plants are diurnal, as they primarily rely on sunlight for energy. In these plants, flowers bloom during the daytime and close at night. In nocturnal plants, on the other hand, flowers are closed throughout the day, but bloom at night to make the most of the presence of pollinators like bats and moths which become active only after dark.
▶ Some examples of diurnal plant species will be gazanias, Venice mallow, etc., while examples of nocturnal plants will include night phlox, moonflowers, angel’s trumpets, etc.
▶ While the term diurnal is derived from the Latin word diurnus, meaning ‘of the day’, the term nocturnal is derived from the Latin word nocturnus, which means belonging to the night.
▶ Some animals have evolved to become nocturnal in order to survive the harsh conditions prevailing in their native habitat. Desert species, for instance, only come out of their burrows after nightfall, as the temperature in deserts is mostly unbearable during the daytime. As for diurnal animals in the desert, they reduce their activities by resting in the shade when the heat becomes unbearable.
▶ The cone-shaped cells which dominate the eyes of diurnal species are less sensitive to light, but they can detect color. The eyes of nocturnal species are dominated by rod-shaped cells, which are more sensitive to light, and make it easier for these species to see in the dark, but cannot detect color. It’s not a rule of thumb as such, but diurnal animals are generally blessed with color vision, while nocturnal animals are colorblind.
Nocturnal Animals Special Senses
Besides their rod-shaped cells, nocturnal animals have specially adapted eyesight which helps them see in dark. Their eyes are bigger in proportion to their head and body, and their cornea is relatively larger than that of diurnal species. This feature is obvious in tarsiers and certain species of owls. Nocturnal animals also boast of a well-developed sense of smell and hearing. In fact, species like bats and owls use these senses to move around in pitch-dark surroundings.
Like we said in the beginning, it’s all about taking full advantage of available niches. As most birds of prey are diurnal, it makes sense for rodents to resort to nocturnal behavior. The arrangement also benefits owls, which are among the few nocturnal birds of prey, as there is abundance of prey for them in the form of rodents, and less competition as other birds of prey are diurnal.