Polar bears are iconic Arctic predators, renowned for their presence across icy landscapes. While often associated with land and ice, these animals possess a strong connection to the marine environment. Their life in the Arctic, a region defined by dynamic ice and vast stretches of water, necessitates remarkable aquatic abilities, including the capacity to dive.
Understanding Polar Bear Diving Depths
Polar bears typically undertake shallow dives, commonly reaching depths of 3 to 4.5 meters (9.8-14.8 feet). While they spend much of their swimming time near the surface, these dives are a regular part of their behavior. Most dives are brief, often lasting around 30 seconds, though bears can remain submerged for over a minute in many instances.
More extensive dives have been documented, with some individuals reaching a maximum recorded depth of 13.9 meters. A record dive reached 45 to 50 meters (147.6-164 feet). The longest recorded duration for a single dive is 3 minutes and 10 seconds. On average, polar bears can hold their breath for about 2 minutes.
Why Polar Bears Dive
Polar bears primarily dive for hunting. They frequently stalk seals, their main prey, particularly at breathing holes or ice edges. This aquatic approach allows them to stealthily reach seals from below the surface.
Beyond hunting seals, polar bears also dive to pursue seabirds or forage for shellfish and kelp on the shallow seafloor. Diving also serves as a means of navigation, enabling them to move through broken ice or open water. Submerging allows efficient travel between ice floes, offering a more direct route than navigating surface obstacles.
Diving provides a mechanism for thermoregulation. Due to their thick insulating layer, polar bears can overheat, especially after exertion or in warmer conditions. A dip in cold water helps them cool down.
How Polar Bear Physiology Supports Diving
Polar bears possess physical characteristics that facilitate their aquatic capabilities. A thick blubber layer, up to 11 centimeters (4.3 inches) thick, provides insulation against frigid Arctic waters and buoyancy. Their large, partially webbed front paws function as paddles, propelling them with an efficient dog-paddle style. Hind legs are held flat, serving as rudders to guide movement underwater.
Their breath-holding capacity is a key physiological adaptation for diving. Polar bears have large lungs relative to their body size, allowing them to stay submerged for extended periods. During a dive, they activate a dive reflex, slowing their heart rate from around 70 to 5-6 beats per minute; this bradycardia conserves oxygen for longer underwater excursions. Their muscles also contain high levels of myoglobin, a protein storing oxygen. When submerged, polar bears close their nostrils, and their eyes are adapted for clear vision both above and below water, aided by a nictitating membrane.