During Dives In The Deep Ocean, Elephant Seals Take Powernaps
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Elephant seals sleep for just two hours a day |
During these rest periods, the seals enter a state of reduced metabolic activity known as "sleep diving." During sleep diving, the seals remain partially conscious, allowing them to monitor their surroundings and quickly respond to potential threats, such as predators or changes in ocean currents. This behavior allows the seals to maximize their time spent foraging for food while minimizing the energy expended during long, deep dives.
For a long time, it appeared as though African elephants were the best at staying up late. They can make due with around two hours of rest. Other mammals, like koalas (20 hours) and you (at least seven hours and at least one strong cup of coffee), require significantly more.
However, the largest land-based mammals face some competition at sea. A study that was published on Thursday in the journal Science found that northern elephant seals can also live on about two hours of sleep. The investigation discovered that Northern elephant seals rest undeniably less adrift than they in all actuality do ashore, and the z's they truly do get adrift are captured many feet beneath the sea's surface. The authors of the study believe that the seals are able to power nap in the deep without being eaten by hungry predators.
Northern elephant seals, which can be found along the West Coast, are excellent divers who can reach depths of 2,500 feet and remain there for approximately two hours. They are not as large as possible elephants, however guys can weigh as much as a vehicle and stretch 13 feet in length. Northern elephant seals must consume fish and squid for approximately seven months each year in order to maintain their blubbery mass.
The seals are at risk of being eaten by killer whales and great white sharks on these epic journeys. Dolphins and fur seals, for example, can rest half of their brains at once. This sort of sleep, known as unihemispheric rest, empowers a vertebrates adrift to nap with one eye open, in a real sense, which keeps hunters from surprising them. However, elephant seals sleep just like we do, completely shutting down their brains.
Subsequent to resting for about 10 minutes, the seals would abruptly awaken and advance back to the surface. Some seals sank over 1,000 feet during these sleep dives, occasionally ending up on the seafloor.
Each day, the seals Dr. Kendall-Bar and her colleagues monitored took multiple sleep dives, giving them approximately two hours of sleep. Northern elephant seals sleep for more than 10 hours per day when they come to land to breed and molt. The seals aren't eating during that time, which could be why they need more sleep.
Jerome Siegel, a psychiatry professor at the University of California, Los Angeles who studies the evolution and function of sleep, stated, "Sleep is an adaptive trait." Animals have developed the ability to sleep in some situations but not others. Dr. Siegel stated that it makes perfect sense that elephant seals would limit the amount of time they sleep while at sea to maximize their food intake and reduce their vulnerability to predators.
Even so, the seals' sleeping patterns are still impressive.
Elephant Seals Sleep For Just Two Hours a Day
It is not entirely accurate to say that elephant seals sleep for just two hours a day. While it is true that elephant seals can hold their breath for up to two hours during deep dives, they actually sleep for much longer periods when they are on land.
Male elephant seals can spend up to three months on land during their breeding season, while females and their pups can remain on land for several weeks to months after giving birth. During this time, they typically sleep for several hours at a time, often in the form of long naps that last for several hours.
While the exact amount of time that elephant seals sleep on land can vary depending on various factors, such as age and sex, it is generally accepted that they sleep for much longer periods on land than they do during their deep ocean dives. Therefore, it would be more accurate to say that elephant seals sleep for just two hours at a time during deep dives, rather than for just two hours a day.
It may appear as though a seal is living the ultimate life of leisure while dozing on the beach. However, cutting-edge research has shown that while doing deep dives, elephant seals sleep for the majority of their lives for just two hours per day in a series of brief naps.
The first study to record brain activity in a free-ranging, wild marine mammal found that elephant seals compete with African elephants for the record for the fewest hours of sleep among all mammals during the months they spend at sea. During deep, 30-minute dives, the seals were found to typically sleep for 10-minute bursts, often spiraling downward while dreaming and occasionally lying down on the seafloor for a nap.
Senior author Prof. Daniel Costa, a marine ecologist at the University of California, Santa Cruz, stated, "For years, one of the central questions about elephant seals has been when do they sleep." During what we call "drift dives," when they stop swimming and slowly sink, we assumed they were sleeping, but we really didn't know.
For more than 25 years, Costa's lab has been monitoring elephant seals at the Ao Nuevo reserve using increasingly sophisticated tags to monitor the seals' movements and diving patterns during their eight-month foraging migrations into the north Pacific Ocean.
Costa continued, "Now we can finally say they are definitely sleeping during those dives, and we also found that they are not sleeping very much overall compared to other mammals."
The scientists believe that the seals can avoid predation by sleeping while diving: they are generally defenseless against hunters, including sharks and executioner whales, while at the sea surface, so they just put in no time flat there to breath between jumps.
The paper's first author, Jessica Kendall-Bar, who developed the system as a graduate student at UC Santa Cruz and now works at UC San Diego, stated, "They’re able to hold their breath for a long time, so they can go into a deep slumber on these dives deep below the surface where it's safe."
In the most recent study, 13 young female seals were given a neoprene headcap to secure sensors that could reliably record brain waves in an electroencephalogram, or EEG, scan. Additionally, accelerometers, time-depth recorders, and other instruments were used to monitor the seals' movements.
"I invested a great deal of energy watching dozing seals," Kendall-Bar said. " In order to ensure that instrumented seals were able to rejoin the colony and were acting naturally, our team kept an eye on them.
The accounts, gathered from the seals during in excess of 100 jumps, uncovered that as they slipped, seals entered a profound rest stage known as sluggish wave rest while keeping a controlled coast descending and afterward entered fast eye-development (REM) rest, when rest loss of motion makes them flip around and float downwards in a "rest winding".
At the profundities at which this occurs, the seals are typically adversely light and keep on falling latently in a wine tool winding like a falling leaf. Elephant seals occasionally rest on the seafloor while sleeping in shallower waters above the continental shelf.
Brain activity of diving seals reveals
One of the key findings of these studies is that diving seals are able to suppress their brain activity during dives, particularly in areas of the brain that control sensory processing and movement. This allows the seals to conserve oxygen and energy while they are underwater, as they are able to remain still and conserve energy without experiencing the need to move or react to external stimuli.
Other studies have shown that seals also exhibit changes in their heart rate and blood flow during deep dives, which help to divert blood and oxygen to essential organs, such as the brain and heart, while reducing blood flow to non-essential tissues. These adaptations allow the seals to remain underwater for longer periods of time while minimizing the risk of oxygen deprivation and other health risks associated with diving.
Overall, these studies on the brain activity of diving seals have provided valuable insights into the physiology and behavior of these remarkable marine mammals, and may have implications for understanding the limits of human diving capabilities and developing new technologies for underwater exploration.