Sleep is a highly dynamic and intricate process that remains poorly understood despite decades of dedicated investigation. While some creatures must stay asleep for the majority of their lives, others appear to flourish on just two hours of sleep every day. Although specific roles of sleep have been recognized or hypothesised, scientists studying sleep are still working to determine the fundamental evolutionary reason for napping. Additionally, the cause of the wide variety in sleep patterns, particularly among animals, is still largely unknown to experts.
Starting with the creatures who catch the most Zs, we will talk about 10 species—five from each category—that sleep the most and the least in this guide.
The Brown-Throated Sloth (Bradypus variegatus) sleeps for 15 to 18 hours a day.
Bradypus variegatus, also known as the brown-throated three-toed sloth, is found in neotropical rainforest regions of Central and South America. These drowsy, sluggish tree-dwellers get 15–18 hours of sleep a day on average.
This species of sloth is mainly diurnally active, however it can exhibit somewhat variable activity patterns. It can adjust to a nocturnal or cathemeral (active during portions of the day and night) activity pattern, depending on its surroundings, the populations of neighboring predators, and the availability of food.
Owl Monkey (Aotus spp.)- 17 Hours
The owl monkey (Aotus spp.), sometimes referred to as the night monkey, is the only genus of genuine monkeys that is nocturnal. These unusual primates live in South and Central American rainforests. During the night, they forage on fruits, flower nectar, foliage, insects, and occasionally tiny birds and mammals among the canopy of trees.
The owl monkey sleeps in family groups in tree hollows, thickets, or trees wrapped in vines when they are not in motion.
The North American Opossum (Didelphis virginiana) sleeps about eighteen hours a day, on average.
The North American opossum (Didelphis virginiana), which is mostly nocturnal, especially under favorable conditions with enough of food, usually spends its days sleeping. This northern marsupial sleeps eighteen hours a day on average when it’s healthy.
The North American opossum is a highly migratory animal that spends much of its daytime hours searching for food and suitable spots to sleep. They live in burrows, open crawl spaces, hollow logs and trees, abandoned dens, shrubs, and brush piles.
Male African Lion (Panthera leo)- 18-20 Hours
Male African lions (Panthera leo) sleep an average of 18–20 hours a day, compared to their female counterparts’ 15–18 hours. These large cats spend most of their days napping in the shade, and they are most active from twilight to dawn.
Healthy adult African lions can sleep outside amid nocturnal animals because they don’t have any natural predators. Researchers frequently come across a large male lion curled up on his belly with his paws in the air! Because they are such gregarious animals, they can alternate resting while other pride members keep a close check on their pups and the surrounding area.
Animals That Sleep the Most: Koala (Phascolarctos cinereus)- 18-22 Hours
Like sloths, the koala (Phascolarctos cinereus) is well-known for their drowsy lifestyle. Because of their heavy digesting and low-energy diet of eucalyptus leaves, koalas sleep up to an incredible 91.67% of their lives! This Australian marsupial sleeps eighteen to twenty-two hours a day on average.
Primarily active around night and dawn (albeit for only 2-6 hours), arboreal koalas graze nearly exclusively on the leaves of eucalyptus trees. Because eucalyptus leaves are highly toxic, they must undergo a protracted digestive process before they can be consumed. In their elongated caecum, koalas harbor specialized microbial populations that are essential for breaking down this hazardous plant matter. They spend long hours sleeping during this intense digestive process.
Animals That Sleep the Least
According to a 2005 study that was published in Nature, there may be a relationship between a herbivorous mammal’s size and how much sleep it needs, with daily sleep hours frequently declining as body size grew. This relationship between size and sleep doesn’t appear to hold true for mammalian predators.
Large herbivorous mammals may need to spend much of their time making sure they are getting adequate calories, which could explain why they sleep so infrequently. Researchers in a 2007 study hypothesized that the slower body and brain metabolic rates of these huge mammals are related to their lowered sleep needs. The reason for this is because elevated metabolic rates may result in heightened cellular damage, necessitating extended periods of rest for the brain to recuperate. Therefore, the researchers hypothesized, lower metabolic rates in large herbivores lead to less cellular damage and a lower need for sleep for cellular repair.
Animals That Sleep the Least: Grey Seal (Halichoerus grypus)- 6 Hours
The North Atlantic’s temperate and subarctic waters are home to the grey seal (Halichoerus grypus). A rocky shoreline close to small islands and reefs is their optimum environment. These marine mammals are diurnal, meaning they spend the majority of the day sleeping and being active.
Many sleeping habits have been adopted by grey seals. For 20 to 30 minutes at a period, they can sleep vertically in the water, with their heads bobbing above the surface or even entirely beneath. They sleep in brief bursts to better evade predators while on land, where they snooze on ice and along the coast. Grey seals sleep for roughly six hours every twenty-four hours.
Domestic Goat (Capra hircus)- 5 Hours
A diurnal mammal, the domestic goat (Capra hircus) is most active in the morning and early evening. These ruminants sleep for up to five hours at night during the course of a 24-hour period, however they will occasionally take quick naps during the day.
Although they only sleep for short amounts of time while standing, they will fall asleep both lying down and standing up. When they feel safe and there are other herd members keeping an eye on them, goats usually prefer to sleep on their backs. They fall into a deep, peaceful sleep at this time. Goats prefer to sleep in groups and tend to doze off together.
Animals That Sleep the Least: Giraffes (Giraffa spp.)- 4 Hours
Giraffes (Giraffa spp.) receive some of the shortest sleep of any mammal, while being the tallest animals on the earth. Giraffes usually sleep for four hours out of every twenty-four hours.
Giraffes sleep in brief cycles of up to 35 minutes, mostly at night, with the majority of naps lasting only around 5 minutes at a time, in order to better defend themselves. They usually sleep on their backs with their head propped up on their rump and their long neck coiled around them. They might stand up and sleep for a short while during the day.
Donkey (Equus asinus)- 3 Hours
Donkeys (Equus asinus), both domesticated and wild subspecies, typically sleep for three hours every twenty-four hours. These gregarious, nocturnal mammals typically sleep in groups at night, with each member taking shifts keeping an eye out for any threats.
Donkeys need to be lying down in order to go into the REM phase of sleep. They usually lie upright with their legs folded underneath, rarely sleeping on their sides.
The African Elephant (Elephantidae) sleeps the least, averaging two hours per night.
The enormous, majestic African elephant (Loxodonta africana) only needs two hours of sleep every twenty-four hours in the wild. These creatures are mostly nocturnal, however they do occasionally take short naps during the day. They sleep most of the time at night.
African elephants are highly gregarious and form close-knit families. They alternate sleeping patterns to protect themselves from sly nighttime predators. Adults usually sleep for periods of five to thirty minutes at a time while standing up. It is more common for calves to sleep on their sides under the supervision of an adult family member.