Seals are able to break diving records due to their ability to store large amounts of oxygen in their blood and muscles, as well as slow down their heart rate to save their oxygen consumption.
Seals have a world-class anatomy for diving. First of all, their lungs are special: they compress during deep dives, which prevents dangerous gases (like nitrogen) from accumulating in their blood—clever! Next, they have very special muscles, packed with myoglobin, a protein capable of storing a huge amount of oxygen—much better than in us! On the blood side, the same story: their blood volume is significantly higher than ours, allowing them to carry more oxygen in reserve. Not to mention their streamlined flippers and torpedo-shaped body, ideal for swimming fast with maximum energy efficiency. All of this combined makes them extraordinary natural free divers.
Seals have much more myoglobin in their muscles than most other mammals. This ultra-useful protein efficiently binds oxygen, creating a significant muscular reserve that allows them to stay underwater longer without breathing. Additionally, their bodies concentrate most of the available oxygen towards the most vital organs (heart, brain), limiting its use in less priority areas. When they dive, their heart rate drops severely: this is called bradycardia, a highly effective natural trick to conserve their O2 reserves. These combined strategies enable seals to perform longer dives and greatly extend their ability to remain underwater safely.
When a seal dives, its body automatically activates certain highly effective physiological reflexes. First, it significantly slows down its heart rate, a phenomenon known as bradycardia. This mechanism conserves a lot of energy and especially limits the consumption of oxygen, allowing it to remain underwater longer without any issues. Another clever phenomenon is peripheral vasoconstriction. Blood is directed away from secondary areas like the skin or peripheral muscles to prioritize the heart, brain, and other essential organs. As a result, even if a seal extends its dive, the vital organs continue to function well. Some parts of the body even briefly switch to "economy" mode to cope with the temporary lack of oxygen. All of this makes their bodies ultra-efficient at withstanding the pressure and duration of their incredible dives. Not bad tricks, huh?
Seals have a thick layer of fat called blubber: it is a giant energy reserve and a highly effective thermal insulator. This fat layer significantly reduces heat loss in icy water and protects vital organs during deep and prolonged dives. Because of this, they maintain a constant body temperature without overexerting their bodies. Instead of wasting their energy on constant body heating, they conserve their resources to catch their prey and stay submerged longer. Less calories wasted unnecessarily, more time and energy to dive deep and for extended periods.
Seals use elaborate strategies to efficiently capture their prey. They often favor an ambush approach, remaining still underwater to surprise fish or squid at the right moment. Some seals dive to great depths, vertically following their prey in a technique called vertical pursuit. Others excel at auditory and visual spotting, taking advantage of the slightest vibration or movement of their dinner to precisely adjust their attack. They also optimize their movements by targeting areas where food density is highest, conserving their precious energy reserves and allowing them to stay underwater longer. Many practice solo hunting, but some species occasionally collaborate during more complicated hunts, thereby increasing their chances of securing a feast while limiting individual effort.
The Weddell seal holds one of the most impressive diving records among seals, regularly diving to depths of over 600 meters and staying underwater for up to 80 minutes.
When they dive, seals voluntarily reduce their heart rate to less than ten beats per minute, which allows them to conserve significantly on oxygen during their underwater excursions.
Unlike humans, seals store a large part of their oxygen not in their lungs, but directly in their muscles thanks to a specific protein called 'myoglobin', which gives them exceptional endurance while diving.
To protect their brains and hearts during deep dives, seals can direct most of their oxygenated blood reserve towards these vital organs by reducing blood circulation to their skin and extremities.
Seals have physiological adaptations such as selective lung collapse and efficient management of oxygen reserves. This allows them to minimize the accumulation of nitrogen in their bodies, thus avoiding the risks of decompression sickness.
Depending on the species, seals primarily feed on fish, squid, octopuses, or even crustaceans. Their deep dives allow them to access abundant food sources that are inaccessible to their terrestrial predators.
The main natural predators of seals are orcas and great white sharks. On land, young seals can also be threatened by predators such as foxes and polar bears, depending on the geographical location.
Most seal species can remain underwater for about 20 to 30 minutes, but some species, like the southern elephant seal, can easily exceed 90 minutes and even reach up to two hours due to their extraordinary physiological and anatomical adaptations.
Some seals, like the southern elephant seal, can dive deeper than 2000 meters and stay underwater for over two hours, setting a true record among marine mammals.
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