Are Bears Nocturnal Or Diurnal? Their Sleep Behavior Explained

Are bears nocturnal or diurnal? Or perhaps crepuscular? The answer is not conveniently straightforward. In part because there are several different species of bears spread across many diverse environments. Bears have long held a fascination for humans. Young cubs can be cute and charming. Full-grown adults in their prime are magnificent, powerful animals. Let’s take a closer look at these impressive animals by examining their waking and sleeping behaviors.

What Are Bears – In a Nutshell?

Bears are mammals with stocky bodies and limbs, non-retractable claws, prominent snouts, and stubby tails. These mammals eat both animal and plant food. We should quickly point to the one exception – the Giant Panda. This popular family member is strictly vegetarian, subsisting on little more than bamboo. Bears have evolved over thousands of years and have successfully inhabited large swathes of the Northern hemisphere. Bears are comparatively large mammals. In fact, the bear is recognized as the largest living carnivore walking the earth.

How Many Bear Species Are There?

There are eight recognized bear species. We list the species below together with their dominant habitats:

• North American Black Bear – North America, Alaska
• Brown Bear (including the Grizzly) – North America, Alaska
• Asiatic Black Bear – Eurasia, Russia
• Polar Bear – Arctic Polar Regions, Alaska
• Spectacled Bear – Andes, South America
• Sloth Bear – India and the Asian subcontinent
• Sun Bear – S.E. Asia
• Panda Bear – China

Polar and brown bears are the largest bear species. Full-grown adult males can exceed 1,500 pounds in body weight. The sun bear is the smallest bear but are these animals nocturnal or not?

Are Bears Nocturnal or Diurnal?

Are bears nocturnal, diurnal or crepuscular animals? Experts can’t always agree on this question. However, they agree that bears are primarily crepuscular and diurnal rather than nocturnal. Most species are active during the day when they forage, hunt, and scavenge. Giant Pandas munch happily on bamboo in the morning and afternoon. Expert foragers like black and sun bears take advantage of twilight hours to gather berries, nuts, fruits, insects, and honey.  

But there are exceptions, like the brown bears of Scandinavia that may hunt at night. Also, polar bears and brown bears display nocturnal behavior. Polar bears and brown bears are considered crepuscular. Yet these bear species engage in nocturnal hunting behavior. One study also showed grizzlies killing most of their elk victims at night. At the same time, polar bears will attack and kill seals after dark if the opportunity presents itself.

IMAGE: Polar bear. CAPTION; Several bear species like polar, grizzly, and Scandinavian brown bears may hunt at night despite not being nocturnal predators.

What Factors Cause Bears to Shift Their Activity Patterns?

Only people and other bears are a threat to this apex predator’s wellbeing, so this animal only changes its activity patterns if threatened. Bears are known to become more nocturnal to avoid human daytime activity.

Research also shows that seasonal factors affect bear activity levels. Many bears must maximize food consumption in the fall to prepare for food scarcity and hibernation. And if unable to scavenge adequate sustenance in its normal cycle, a bear may shift its hunting and foraging into the night hours.

In addition, climate change and human encroachment are causing a change in previously observed bear activity behavior. For example, climate change is melting arctic ice flows making it more difficult for polar bears to hunt their traditional prey. A shortage of food forces this bear species to find other food sources. At times, these alternatives can include consuming the carcasses of other bears.

Do Bears See Humans as Food?

The big bears are immensely powerful beasts. For the most part, these apex predators target other animals. However, attacks on humans have become a pretty regular occurrence. Over the years, there have been numerous recorded incidents of bears attacking humans. Many of these have taken place within North America’s National Parks. Alarmingly, in many attacks, the bear has specifically targeted the person as prey. Brown bears, black bears, polar and sloth bears have all perpetrated such attacks.

Bears smell campsite cooking and the camper’s provisions and associate humans with food. Once a bear becomes accustomed to humans as part of its environment, it stops seeing people as a threat. This situation is dangerous. Besides, bear attacks on people are more likely during the day when both parties are more active. But nocturnal attacks are possible if a bear is hungry or rogue and no longer afraid of people.  

For How Long do Bears Sleep?

Besides winter sleep habits, many bears sleep a similar number of hours to humans. The difference is that bears typically sleep in short nocturnal and diurnal spells instead of one block. Different bear species also sleep for various lengths of time. When grizzlies are most active hunting and scavenging, they only sleep an estimated 4 hours daily. In contrast, black and polar bears may nap for 6 to 7 hours. If bamboo is abundant and accessible, Pandas can easily sleep for over half the day between meals.

These massive mammals are also comfortable sleeping in the open. Alternatively, they seek shelter in caves, tree cavities, brush piles, under logs, and amongst bamboo plants. Some bears sleep in trees, like Giant Pandas, or dig shallow divots in the snow, like polar bears.

Why Pandas March to Their Own Beat?

Pandas are the only bears that are not carnivorous. However, the Panda’s digestive system is more like that of a carnivore than a herbivore. As a result, the bulk of what the Panda eats passes as waste. In fact, the Giant Panda bear only digests about 20% of what it consumes. This low consumption rate means they must eat plenty of bamboo to meet their nutritional requirements. 

Giant Pandas don’t have any natural predators, so unlike other herbivores, they can forage and feed without fear. Since they’re not predators, they don’t need to sync their timing to other animals’ movements. Pandas have the luxury of choosing their own hours. An interesting study observed that Pandas are active during three peak periods – in the morning, afternoon, and midnight. In between these peak phases, these previously endangered animals rest and sleep to support their digestion. Consequently, instead of being nocturnal, Giant Panda bears are more cathemeral.

Do Bears Hibernate?

Most bears practice a form of hibernation in winter. Winter means food scarcity and severe weather conditions, encouraging bears to become inactive. This dormant period lasts two to five months, depending on the weather conditions. Bears are suitably adapted to survive this lengthy spell of near inactivity, having accumulated fat reserves in earlier months. Their metabolism slows, and their body temperature adjusts to conserve energy and stay warm as they ride out the winter. 

But despite popular belief, bears don’t sleep the whole time they are hibernating. They move about and change position periodically. This minimum movement helps bears to conserve heat and stay comfortable. In terms of eating, drinking, and bodily functions, amazingly, none of these commonly essential bodily functions are necessary during hibernation. Instead, hibernating bears form a plug in their rear ends, ensuring they do not need to leave their dens in the winter.

However, not all bears hibernate. Polar bears remain active during winter because winter brings more ice and better hunting. 

Do Bears Have Good Nocturnal and Diurnal Eyesight?

Bears are resilient, adaptable animals that have proven their ability to survive and thrive in different light conditions, including gloom and darkness. Predatory animals depend on binocular vision to provide depth of field while hunting. A high density of receptor cones in the eye structure supports good binocular vision. 

Several species, including black, brown, and polar bears, possess concentrated cone density in the eyes. As such, these bears are thought to have an element of all-important binocular vision. Bears also have excellent smell and hearing. These significantly well-developed senses and their adequate vision equip the average bear to navigate its environment confidently.

Nocturnal vs. Diurnal: What’s The Difference?

Navigate to Nocturnal vs. Diurnal: What’s The Difference? for further information about the nocturnal and diurnal phenomenon in various living creatures.

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The photo featured at the top of this post is © iStock.com/James Moore