Duration & Schedule

| Amount of Sleep | When | Napping Animals |

Amount of Sleep

In studying over 150 different species of animals, scientists have found that how long animals sleep seems to depend on size and metabolism. (1) Generally, larger animals (with a relatively low metabolic rate) tend to sleep less than smaller animals (with a relatively high metabolic rate). However, humans need about the same amount of sleep on average as either a pig or a guinea pig, and not as much as a chimpanzee or gorilla.

Average amount of sleep per day for mammals (2)

When Animals Sleep

Some animals are nocturnal, active during the night, and others are diurnal, active during the day. This creates a good balance: nocturnal predators share their prey and diurnal predators share their prey. Animals adapt to certain sleep patterns to avoid competition for survival.

Diurnal animals 'set their clocks' with daybreak, or dawn, whereas nocturnal animals use dusk. Under controls of constant light, nocturnal animals will tend to lengthen the cycle whereas diurnal animals tend to speed it up. For example, a mouse's cycle under light controls would be about 25.5 hours whereas a diurnal bird's might be about 22 hours.

A third typical sleep/wake pattern is that of Crepuscular animals, which are twilight active.

Diurnal - Diurnal animals normally sleep during the night and are awake during the day. Humans are diurnal.

Many diurnal animals, including mammals and invertebrates, have a harder time learning in the night than during the day, or even functioning well. It even takes an earth worm 40% longer to learn a single turn in a T-shaped maze! (4)

Nocturnal - Nocturnal animals normally sleep during the day and are awake at night. For some of these animals, such as rabbits and red foxes, their native sleep patterns have been disturbed by human interference, and the animals must adjust to survive. See our Nocturnal Animals Lesson Plan.

Just a few of the many nocturnal animals include:

• American Porcupine
• Armadillo
• Bat
• Bush baby (who folds up own ears for warmth and quiet)
• Fox (5)
• Koala
• Loris
• Opossum
• Owl
• Raccoon
• Rhinoceros
• Tiger
• Toad and some Frogs
• Weasel
• Whippoorwill (or Nightjar) (who eats mosquitos and moths)
• Wolf

Add to our growing list of nocturnal animals. See what we have so far!

Interact! Animal Crossword Puzzles # 7, 9, and 11-14 feature nocturnal animals.

A TQ Junior 1999 Award Winning site: Creatures of the Night and You features nocturnal animals and includes several interactive ideas.

Crepuscular - Crepuscular animals are most active during twilight: both at dawn and dusk. These animals include the platypus, rodents, and deer . Rattlesnakes and gila monsters are crepuscular as are a number of desert animals, who adapt this way to optimize access to water. (6) Rabbits and Brown bears are two animals often thought to be nocturnal which actually be crepuscular.(7) The wallaby is actually both crepuscular and nocturnal, another animal that doesn't fit neatly into one category. (8)

Many tropical rain forest dwellers are crepuscular. The rest are primarily nocturnal. (9)

Variations in Sleep Cycles

Badgers are nocturnal most of the year. During the summer, when the days get longer, their bodies do not adjust and are therefore awake for some of the day. Bobcats are nocturnal in summer, diurnal in winter.

The Nightjar, a European bird, is not only nocturnal, but has a circalunar rhythm as well as a circadian rhythm. When the moon is full, it will come out later than usual. It waits for the moonlight to come out so that it can hunt insects more easily. These birds usually mate so that their chicks will be a few days old at full moon. This way, the parents have longer to hunt for food for their chicks.

Physical Changes During the Night

• Anoles, also called American Chameleons, change color even when sleeping! This is because these anoles change color as the temperature changes. The pigments in the skin of an anole turn brown when it is cold and green when it is warm.
• Crabs' pigments become lighter in color at night.
• Fireflies and dinoflagellates produce light during the night.
• Insects and Crustaceans become more sensitive to light during the night because pigments around their eyes will migrate.
• Mammals' body temperatures drop during the night, urine production drops, and their metabolic rates drop.

Napping Animals

Many carnivores take several naps during the day. Those who don't have to worry about being hunted have the freedom to sleep in broad daylight. Domestic cats, secure in their lifestyle, feel free to nap on and off throughout the day and night, source of the idiomatic expression: "Cat nap."

Ostriches specialize in napping, never sleeping for more than 15 minutes at a time. (10)

Rabbits take many short naps throughout the day. However, in contrast to the secure lions who can sleep for hours at a time, rabbits' naps are very short. This is because they must be alert and protect themselves from danger. Except when their preferred schedule is interfered with by humans, rabbits are considered to be nocturnal by many sources, although we also saw them referred to as crepuscular, which may well be closer to their original situation. (11)

(1) Lavie, Peretz. The Enhchanted World of Sleep. New Haven: Yale University Press, 1996. p. 101.

(2) MOST of the information from this chart was taken from MANY sources. See our references page.

(3) Coren, Stanley. Sleep Thieves: an Eye-Opening Exploration into the Science & Mysteries of Sleep. New York: The Free Press, 1996.p. 42

(4) Nightwatch: the Natural World from dusk to dawn. New York, Facts on File. 1983. p. 145

(5) Images of gray fox found at: Desert USA website, http://www.desertusa.com, (Royo, A.R. "Desert animal adaptations," DesertUSA magazine, June 1999. URL: http://www.desertus.com/survive.html) Jim Bremner jim@dwmi.com, July 19, 1999. Email message.

(6) House Rabbit Society, "True or false? Rabbits are nocturnal"(False) URL: http://www.rabbit.org/fun/answer6.html AND http://www.sfzoo.com/html/map.bears.html

(7)For platypus and wallaby together-- "Animals." URL: http://www.smithfieshs.qld.edu.au/Wet_Tropics/Animals.html web site by Smithfield High School PO Box 500 Smithfield, Queensland Australia 4878)

(8) Attmore, Stephen. Animal Encyclopedia. England: Brimax Books, Ltd.1987. p. 148

(9)Nightwatch: the Natural World from dusk to dawn. New York, Facts on File. 1983. p. 14-15

(10) Attmore, Stephen. Animal Encyclopedia. England: Brimax Books, Ltd.1987. p. 142

(11) "Living Arrangements." House Rabbit Resource Network. Last modified: December 01, 1998. URL: http://www.geocities.com/Heartland/Ranch/8093/living.html.