Nocturnal

What "nocturnal" means

A nocturnal animal is active mainly at night and sleeps or rests during the day. The behavior is called nocturnality.

Nocturnal is one of several activity patterns biologists use:

• Nocturnal: active at night
• Diurnal: active during the day
• Crepuscular: most active at dawn and dusk
• Cathemeral: active at irregular times, day or night

The lines aren't always sharp. Plenty of animals described as nocturnal are really crepuscular, and many nocturnal species will come out by day when food is easy to get.

Why some animals are active at night

Night activity gives animals several advantages:

• Avoiding predators. Darkness is a form of camouflage.
• Less competition. Hawks and owls can hunt the same meadow for the same rodents because hawks hunt by day and owls by night.
• Catching prey off guard. Many prey animals don't see well in the dark.
• Beating the heat. In deserts, staying underground by day and coming out at night saves water. The fennec fox is most active during cooler nighttime hours.

How nocturnal animals are built for the dark

Nocturnal species often have heightened hearing and smell and eyes adapted to low light. Owls and tarsiers have very large eyes for their body size. The great horned owl has asymmetrical ear openings that help it pinpoint prey by sound. Many bats use echolocation to find food in the dark.

Nocturnal animals you can see at the zoo

Well-known nocturnal zoo animals include:

• the raccoon
• the Virginia opossum
• the two-toed sloth
• the nine-banded armadillo, which often comes out to forage around dusk
• the binturong, which is mostly nocturnal but also active at dawn and dusk
• most bats, owls and kiwi

What it means for your zoo visit

Nocturnal animals are often curled up asleep during normal zoo hours. A few tips:

• Look for a nocturnal house or "night" exhibit. Some zoos keep night-active species in dimly lit buildings, and some reverse the light cycle so the animals are awake while visitors are there.
• Go early or late. Arrive at opening or stay until near closing, when many animals are more likely to be moving.
• Check feeding times and keeper talks. Scheduled feedings and enrichment sessions are a good chance to see a sleepy animal in action.
• Look carefully. A resting animal is often tucked into a nest box, hollow log or the top of a tree.

Find a zoo near you in our zoo directory.