Many Australian animals have a nocturnal lifestyle. That is, they are usually active at night. They feed and move about in the darkness. Australia's long isolation from the rest of the world and the extreme aridity of the land has resulted in these animals evolving characteristics suitable for their unique environment. The most noticeable of these, of course, is their nocturnal lifestyle.
Animals can be categorised into three broad groups based on the time of day that they are most active.
Diurnal (Daylight) animals are usually active during daylight and rest when it gets dark.
Crepuscular (Twilight) animals are active during dawn and dusk (twilight) and rest at other times of the day.
Nocturnal (Night) animals are those that are active during the night when it's totally dark and rest during other times of the day.
Most animals, however, don't fit conveniently into these categories as they may be seen to be active across these time-zones and may adjust their behaviour to a number of factors – typically the climate.
Some animals, such as bats and owls, are strictly nocturnal. Others, such as the echidna and red bellied black snake, vary the times they are active according to their environment. For example, if the climate is hot, the echidna will forage for food at night. But in cooler weather, it will come out during the day. While the echidna's behaviour is dictated by its desire to stay cool, in the case of the red bellied black snake, it is just the opposite. Being cold-blooded and needing to stay warm, the snake will hunt at night if the weather is hot. But if the weather is cold it will do so during the day. Kangaroos, on the other hand, while officially categorised as nocturnal are also crepuscular, being quite active during dawn and dusk.
It is common practice to classify many animals that come out when it gets dark as nocturnal, even though in actual fact they may be crepuscular animals. One reason might be the tongue-twisting name – crepuscular – which few can remember or pronounce.
Australia is the driest inhabited continent on earth. Most of the land is arid and the climate is hot. As a result many of the native animals, especially the marsupials, have adopted a nocturnal lifestyle in order to avoid the blistering heat of the day. This behaviour of coming out only at night when the temperature is cooler conserves precious water which would be lost by being active in the hot sun.
Nocturnal animals have evolved special adaptations that help them survive in the dark.
Many nocturnal animals, such as possums, have very good low-light eyesight.
Many nocturnal animals, such as the kangaroo, bilby and rabbit have an acute sense of hearing. This allows them to detect danger at great distances in the dark. Many bats, on the other hand, use echolocation which acts like a radar. The bat emit a high-frequency sound which bounces off objects, the animals ears pick up the bounced signals and help it navigate through the dark.
Some of these animals have an acute sense of smell. The koala's large nose for example allows it to sniff out the most appropriate leaves to eat in the dark.