Are Whales Nocturnal? [Whales’ Activity Factors]

Depending on the season, food availability, environment and time of day, both nocturnal and diurnal whales may have varying activity periods or rest intervals.

What’s more, these factors are constantly changing, so their behaviour can adapt to meet new needs in different scenarios.

So, there is no one-size fit answer to the question, “Are whales nocturnal?” And in this article, we will see the detail in depth.

Are There Whales Nocturnal or Diurnal?

There are both species of nocturnal and diurnal whales. However, in terms of ratio, most are nocturnal species.

Some species of the whale will be more active during the night and sleep for much of the day. Their behaviour is largely governed by food availability in their environment. For example, baleen whales such as humpback whales have been observed feeding at night due to the abundance of krill, their main source of food.

On the other hand, some species, such as sperm whales and blue whales, are mainly diurnal. They take advantage of the abundant sources of squid during the day and often tend to be more active in shallow waters during daylight hours.

Some whale species also use nocturnal behaviour as a way to avoid predators. For example, killer whales are known to hunt during the day and sleep at night.

Additionally, several external components influence whales’ activity cycles, which will be further explored later.

Which Factors Affect Whales’ Activity Periods?

Whale behaviour is largely determined by external factors such as food availability, season, environment, and time of day.

Food Availability

Food availability is a major factor that influences whales’ activity periods. Whales are creatures of habit and will consistently return to areas where they had the most successful hunt for food.

Depending on the breed, whales’ primary diet can range from zooplankton to larger prey such as fish and marine mammals. Regardless of their particular species’ preferences, consistent access to food is essential for a whale’s survival.

When food sources become scarce, whales will need to find alternative sources of sustenance either by migrating to different areas or changing their behaviour patterns to ensure that they can continue hunting for food in the same area.

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The season is also an important factor when considering the activity period of whales since this impacts the presence and availability of prey. During winter, when temperatures drop significantly and sea conditions become rough, whales may be forced to migrate further south towards warmer waters or even hibernate to conserve energy.


On the other hand, during summer months, when there is more sunlight and warm water temperatures, whale populations tend to increase due to increased reproduction rates as well as an influx of prey into those areas due to seasonal changes in oceanic currents and weather systems.

As such, whale activity tends to peak during these months, with individuals moving around much more frequently than throughout other seasons.


The environment is another factor that heavily impacts the activity period of whales since different geographical regions contain different resources necessary for survival.

For example, some coastal environments may provide access to a variety of fish species which serve as primary sources of nutrition for certain types of baleen whales; however, these same environments may also be more prone to human disturbance, which could cause changes in local whale behaviour patterns due to fear or stress responses.

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On the other hand, deeper waters away from shorelines may provide greater safety from potential predator encounters but less abundant supplies of food overall due to reduced biodiversity near surface levels; thus forcing certain species, such as Orcas, who require larger prey items faster, to hunt strategies over longer distances.

Time of the Day

The time of the day can influence the habits of certain whale species showing diurnal behaviours – they are active during daylight hours and rest at night. While orcas or pilot whales tend to hunt in darkness, so their targets cannot ascertain them easily due to low visibility underwater, smaller cetaceans like dolphins or porpoises that lack such protection prefer daytime activity since they’re more vulnerable out on the sea.

During the day, diurnal cetaceans typically stay close to shorelines where there are higher concentrations of plankton blooms – an easy source for quick nutrient replenishment.

Meanwhile, at night, nocturnal cetaceans often move further out into open seas in order to take advantage of their sophisticated echolocation techniques that have been developed over time and can be used to locate larger schools of fish with sound waves emitted underwater. This allows them to hunt more efficiently during dark hours when visibility is reduced beneath the surface.

What Do Whales Do During the Night?

Whales have long been a source of mystery, with behaviour that has mesmerized us for centuries. One of the most curious mysteries is what whales do at night. After many years of research, scientists uncovered some amazing insights into whale activity during night-time hours.

Sleep & Resting

Just like humans, diurnal whales, like blue whales, experience periods of sleep and rest during the night. Diurnal whales can sleep in two ways – unihemispheric slow-wave sleep (USWS) and bihemispheric slow-wave sleep (BSWS). USWS is when a whale sleeps with one side of its brain at a time, so it can stay alert while also getting some rest.

BSWS happens when both sides of the brain enter slow-wave sleep at the same time, allowing for deeper rest. In addition to sleeping and resting, whales also perform gentle vocalizations or movements called logging.

This form of nighttime activity is typically seen in some nocturnal female humpback whales who remain still at the surface for long periods before diving down again.


Nocturnal whales become active during the night. Depending on their species and habitat location, they may hunt or feed at night. For instance, sperm whales will hunt squid deep underwater using echolocation.

This type of feeding behaviour generally occurs around dusk and dawn but has been observed as late as midnight in some cases.

Other species, such as humpback whales, tend to feed more on krill closer to shorelines from sunset until sunrise, although some have been found hunting even after dark.

Additionally, some species localize their feeding habits by season – killer whales may feed mainly in daylight during certain periods but switch to nighttime feeding behaviours when food sources become scarce at other times of the year.

Social Interaction

The night-time hours are not just reserved for sleep or food gathering; many whale species also use this time to interact socially with one another. Some whales may gather in groups known as “singing circles”, where they can be heard making complex vocalizations that seem to serve both social and reproductive functions.

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Similarly, some species, such as blue and bowhead whales, may use sound production for communication purposes throughout the evening’s darkness, possibly helping them locate potential mates or establish dominance over rivals in their pods.

Do Whales Sleep During the Day?

Yes, whales do sleep during the day, although their sleeping patterns differ depending on whether they are nocturnal or diurnal. Nocturnal whales typically sleep during the day and become active at night when it is dark outside. This allows them to take advantage of the cover of darkness while they hunt for food.


Does a whale sleep at night? Yes, diurnal whales, on the other hand, are usually active during the day and will rest at night. While they can sleep in segments over a 24-hour period, most of their rest time is shifted towards night-time hours in order to conserve energy for daytime activities such as foraging and socializing with other members of their species.

Whales have been known to sleep for short periods throughout the day in shallow and deep waters. During these short resting episodes, whales often float beneath the surface of the water and may even slow down or stop breathing completely for a few seconds as part of their natural sleeping behaviour.

They may also rest at depths between 600 feet and 1,000 feet, which can help protect them from predators while they catch some Zs. In some cases, nocturnal whales will remain submerged underwater during daylight hours to avoid detection by other animals and potential threats from above sea level.

In addition to sleeping during the day, whales will also take more extended naps over several days or weeks to conserve energy and recover from long migrations or difficult activities such as mating rituals or birthing new calves into their pod.

How Many Hours Do Whales Sleep?

Like some other marine mammals, whales are known for sleeping with one half of their brain at a time. This is known as unihemispheric slow-wave sleep, which is mentioned above. In this way, whales can remain alert and keep an eye out for any potential predators or other dangers while they rest.

The amount of sleep that whales get can vary depending on the species. According to research, the larger sperm whale is thought to sleep for only 7% of the day, which works out to be 1.68 hours per day. However, this hasn’t been fully confirmed, and other reports suggest that they may sleep even less than this. While swimming, they often close one eye while the other remains open, suggesting they may be semi-conscious.

Other species of whales, such as belugas, have been observed sleeping with both eyes closed while remaining upright and bobbing at the surface of the water for approximately 3-4 minutes at a time. This has led scientists to believe that these whales are entering into a state known as “logging”, where they are resting but still able to respond immediately if something unexpected comes their way.

Killer whales have also been observed engaging in what appears to be light sleeping or napping behaviour; however, unlike some other species, these whales tend not to enter into a deep sleep state and instead remain alert and responsive despite being relatively inactive for short periods of time.

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Fascinatingly, several whale species have been observed to sleep anywhere from a few minutes to an hour each day. For example, the humpback whale has been observed sleeping for up to 30 minutes in one sitting. It is believed that the sleep patterns of these animals are highly dependent on both their environment and activity level.

In addition to sleeping with one-half of their brains at a time, whales can also take short power naps during the day. These power naps usually last anywhere from a few seconds to several minutes and typically occur while the animal is still in motion, such as when they are swimming or migrating. It is believed that taking these short naps helps whales conserve energy and remain active throughout the day.

Little is known about how deep-sea whales sleep since studying them in their natural habitat is difficult. However, it has been speculated that deep-sea whales may need more rest than those living closer to shore due to the fact that they need more energy to navigate through dark waters and locate food sources located further away from them.

Whales can also voluntarily skip sleep altogether when necessary, by entering into a state similar to hypnosis known as “suspended animation.” However, this behaviour has only been observed in captive animals, so it’s unclear how often wild whales do this, if at all.

Can Whales See in The Dark?

Yes, whales can see in the dark. This is due to their eyes containing a high number of rods. Rods are specialized photoreceptor cells that allow organisms to detect objects in low-light conditions. They are sensitive to dim light and help an organism navigate better during the night or in deep ocean regions where light levels drop significantly.


A study conducted by researchers at the University of Hawaii found that while baleen whales have relatively few cones to detect colour, they make up for this with a higher density of rods—so much so that some species have more rods than humans! This allows them to see effectively even in near-total darkness.

The study also revealed that sperm whales have several adaptations that enable them to see well under dim light conditions, including larger pupils, significantly higher densities of rods, retinas with fewer blood vessels, and reflective mirrors behind their retinas.

Furthermore, research has shown that sperm whales (Physeter macrocephalus) have retinal oil droplets which contain two main pigments: iodopsin and rhodopsin. Iodopsin is the pigment used for vision during the day, while rhodopsin is used for vision at night, thus enabling these animals to switch between day and night vision without having to adjust their iris diameter like most other mammals do when moving between different lighting situations.


Hopefully, now you understand that most whales are nocturnal creatures and sleep during the day. Also, other factors like food, environment, and activity level influence their sleep patterns.

To manage their sleep deprivation, they can take short power naps during the day, and some of them are even capable of entering a hypnotic state that allows them to voluntarily skip sleeping altogether when necessary.

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