The aquatic realm is home to mammals with remarkable adaptations for surviving underwater. These creatures possess physiological mechanisms that enable prolonged submersion, even in oxygen-deprived, high-pressure environments.
The Ocean’s Ultimate Breath-Holder
The Cuvier’s Beaked Whale, scientifically known as Ziphius cavirostris, holds the record for the mammal capable of staying underwater the longest. One individual of this species was recorded performing a dive that lasted 222 minutes, or three hours and forty-two minutes. This same species also holds the record for the deepest dive, reaching an incredible depth of 2,992 meters (9,816 feet).
These whales typically inhabit deep pelagic waters, preferring areas around continental slopes, seamounts, and submarine canyons. They are found globally in temperate, subtropical, and tropical oceans. Cuvier’s Beaked Whales are medium-sized with a robust body and a distinctive “goose-like” head profile, feeding primarily on cephalopods like squid and octopus, as well as fish and crustaceans, using a suction feeding method.
The Science of Submersion
Mammals capable of extended underwater dives rely on a suite of physiological adaptations collectively known as the diving reflex. This reflex initiates a series of responses upon immersion, including the cessation of breathing, a significant slowing of the heart rate, and the redirection of blood flow. These changes optimize oxygen conservation and distribution throughout the body.
A core component of this reflex is bradycardia, where the heart rate decreases. For instance, a seal’s heart rate can plummet from around 125 beats per minute to as low as 10 beats per minute during a dive, reducing the heart’s oxygen demand. Simultaneously, peripheral vasoconstriction occurs, constricting blood vessels in less critical areas like muscles and skin. This shunts oxygenated blood to the most sensitive organs, such as the brain and heart, ensuring their continued function.
Diving mammals possess enhanced oxygen storage capacities compared to terrestrial animals. Their blood has higher concentrations of hemoglobin, and their muscles contain abundant myoglobin, a protein that binds and stores large amounts of oxygen for local use. Some species can also contract their spleen, releasing additional oxygen-rich red blood cells into circulation to boost oxygen availability. Furthermore, their lungs are designed to collapse under pressure, forcing air into reinforced airways where gas exchange cannot occur. This mechanism prevents nitrogen from entering the bloodstream at depth, thus avoiding decompression sickness.
Diverse Diving Masters
Beyond the record-holding Cuvier’s Beaked Whale, other aquatic mammals exhibit diving prowess. Sperm whales are exceptional deep divers, regularly descending to 2,000 meters (6,560 feet) for about 45 minutes. Some of their dives can extend to 3,000 meters (9,800 feet) and last up to 90 minutes. These deep dives are primarily for hunting squid, their main prey, found in the ocean’s depths.
Elephant seals are also formidable divers. They can hold their breath for over 100 minutes, making them the longest-duration divers among non-cetacean mammals, with some southern elephant seals recorded for up to two hours. Their dives frequently reach depths between 300 and 600 meters, though Southern elephant seals have been documented diving to 2,388 meters (7,835 feet). They exhale before diving to minimize gas in their bodies, a strategy that helps prevent decompression sickness.
Weddell seals, native to the Antarctic, demonstrate impressive cold-water diving abilities. They can dive to depths of 600 meters (2,000 feet) and remain submerged for up to an hour, with some dives lasting 82 to 96 minutes. These seals utilize cracks and holes in the thick ice for breathing during their foraging expeditions.