What if every animal slept at night?

At night, you go to bed. But outside, some animals are just waking up.

What if every animal went to sleep at night, just like you?

Animals that are active in the daytime and sleep at night, like most people, are called diurnal. Animals that are active at night and rest in the day are called nocturnal. Many animals are nocturnal, from owls and bats to moths and desert foxes.

What if every animal slept at night and was awake only in the daytime? In this thought experiment you will meet some night specialists and find out why the dark suits them, then decide what a world with empty nights might be like.

Daily activity patterns divide animals into diurnal (day-active), nocturnal (night-active) and crepuscular (active at dawn and dusk) species. These schedules are adaptations, and many species are active at night for a combination of reasons.

This thought experiment forces every animal onto a diurnal schedule and asks what would follow for predators that hunt in darkness, for the moths and bats that pollinate and eat insects at night, and for animals that escape daytime heat. The outcomes are reasoned ideas, not predictions.

At night, owls fly quietly and listen for mice. Bats catch insects in the dark.

Moths visit white flowers that smell sweet. The night is busy!

When the sun sets, a night shift begins. Barn owls fly silently over fields, listening for the tiny sounds of mice and voles. Experiments show a barn owl can catch prey in total darkness using only its hearing.

After dark, moths and bats take over the job of pollinating, visiting pale, sweet-smelling flowers. Many bats also eat huge numbers of insects. In the United States, the pest control bats provide for farms is estimated to be worth more than 3.7 billion dollars a year.

The Barn Owl Trust notes that barn owls can capture prey in total darkness by hearing alone: their heart-shaped facial disc channels sound to asymmetrically placed ears, and soft feathers make their flight nearly silent. Their eyes are about twice as light-sensitive as ours.

The USDA Forest Service describes moths and bats as taking over 'the night shift' of pollination, visiting pale, fragrant flowers with copious dilute nectar; some hawkmoths have tongues longer than their bodies. The USGS cites estimates that insect-eating bats save US agriculture over 3.7 billion dollars, and possibly as much as 53 billion dollars, a year in pest control.

If owls slept at night, they might not find mice in the day.

If moths slept at night, some night flowers might not get visitors.

If every animal slept at night, the night shift would vanish. Barn owls, built for hunting in the dark, would have to hunt in daylight, when their silent flight and sharp hearing give them less of an advantage over mice that can see them coming.

Night flowers that rely on moths and bats might not get pollinated. Bats that hunt night-flying insects would have to hunt in the day instead. And desert animals that hide from the midday sun might struggle with the heat.

A fully diurnal fauna would remove nocturnal predation, nocturnal pollination and nocturnal insect control in one stroke. Night-adapted senses, such as owls' hearing-based hunting, might lose much of their value in daylight, and night-blooming plants that depend on moths or bats might set less seed.

Day-active life might also become more crowded: more species competing for the same food in the same hours, with prey and predators all awake together. How ecosystems would rebalance is not predictable; the point is that night is not empty time but a set of niches.

Some animals come out at night to stay cool. Some hide from hungry animals.

Some come out at night because their food comes out at night!

Animals are active at night for different reasons. In hot deserts, night is cooler: fennec foxes hide in their burrows through the hottest part of the day and hunt after dark. For some small animals, darkness makes it harder for predators to spot them. And some hunters, like owls, are out at night because the mice they eat are out too.

The night can also mean less competition. In northern Botswana, big cats and wild dogs share the same land, and hunting at different times of day helps them avoid running into each other: cheetahs usually hunt by day, while lions and leopards are mostly out at night.

The Forest Preserve District of Will County, Illinois, summarizes four commonly proposed advantages of nocturnality: avoiding detection by predators, hunting prey that is itself nocturnal (owls and foxes hunting mice and rats), less competition for food and water, and, in deserts, escaping the heat. The Smithsonian's National Zoo gives a desert example: fennec foxes shelter in burrows through the hottest part of the day and hunt at night.

For competition, the AP's report on a 2023 Botswana study notes that hunting at different times of day is a long-evolved way for the region's large predators to reduce encounters: cheetahs usually hunt by day, lions and leopards mostly at night. These pressures overlap, and the same species may shift its timing with conditions, as a 2023 study of African carnivores showed. A schedule is part of an animal's niche, as much as its food or habitat.

The fennec fox lives in a hot desert. It sleeps in a cool burrow in the day.

At night, when it is cooler, it comes out to find food.

The fennec fox lives in North Africa, across the Sahara Desert and east into Sinai and Arabia. It hides in burrows during the hottest part of the day and comes out at night. Its huge ears help it lose heat and hear prey moving under the sand.

Scientists have seen animals change their timing as the weather changes. In northern Botswana, researchers tracked big cats with GPS collars from 2011 to 2018. On the hottest days, cheetahs became more active at night, the time when lions and leopards are mostly out.

The Smithsonian's National Zoo describes fennec foxes as nocturnal, sheltering in burrows by day to avoid the hottest hours; their large ears dispel heat and locate prey under sand. If every animal were forced into daylight, desert species like this might face heat they normally avoid.

A 2023 study in Proceedings of the Royal Society B, reported by the Associated Press, used eight years of GPS-collar data (2011–2018) from 53 large carnivores in northern Botswana. On the hottest days, with maximums near 45 °C, cheetahs became more nocturnal, and their hunting hours overlapped 16 percent more with those of mostly nocturnal lions and leopards. Timing, it shows, can shift, with consequences.