![]() To do so successfully, they and their descendants developed some expedient evolutionary traits that heightened certain senses to help them survive. Dinosaurs had to hunt by day, and so many mammals chose to live largely nocturnal lives. Early mammals emerged during the Jurassic period, at a time when the world was dominated by cold-blooded dinosaurs with metabolisms that relied on the warmth of the sun. There might be no single reason for an animal’s nocturnality, however there is a popular theory that mammals are intrinsically nocturnal because there were fewer predators at night-specifically reptiles. For other animals living in hot and dry environments, moving around in the cool of night makes sense because it stops them from overheating and wasting precious water. Indeed, with many different animals foraging for the same foods, whether fruits, insects, or animals, if everything hunted during daylight hours then watering holes and hunting grounds would be overcrowded-leading to competition and conflict that some species may not survive. Similarly, for a predator the night-time may be when its preferred prey is more active and therefore easier to find: many small mammals evolved to be nocturnal, and predators match their schedule. ![]() That most mammals have adapted to the dimness of night over the brightness of day suggests strong evolutionary advantages for their behaviour-and there can be big benefits to living life by moonlight.įirst, there is an obvious intrinsic advantage in the darkness itself, with the absence of light helping both hunter and hunted to avoid detection. As well as these nocturnes there are cathemeral animals that are active by both day and night, and an even smaller number of crepuscular animals that come out in the twilight of dusk and dawn. The night attracts many species, from Indian crested porcupines to pygmy hippos, and from coyotes to the Hoffman’s two-toed sloth. While most birds are active during the day, many insects and around 70 percent of mammals are nocturnal, coming out at night to forage for food and to find a mate. But for the nocturnal hunter, it has paid off. A fox leaps out of the shadowy blackness and in a moment the animal’s evolutionary gamble to shun daylight for darkness has failed. ![]() It stops still, listening intently for danger the night provides good cover, but not good enough. As it emerges into the darkness, it uses its heightened sense of smell to sniff for food but catches a sense of something else. ![]() From a burrow hidden in the ground, a mouse cautiously pokes its head out into the cool night air. ![]()
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