By Dr. Becker
Polar bears probably aren’t the first animals that come to mind when you think about impressive divers, but they’re actually incredibly strong swimmers. They have to be – their prey of choice is the seal.
While polar bears often hunt by stalking cracks in Arctic ice where seals come up to breathe, they’re also known to dive for their food. A typical dive lasts anywhere from three to 30 seconds, and the longest polar bear dive ever recorded was one minute, 12 seconds – a dive in which a polar bear searched for kelp to eat.
That makes the newly recorded dive even more impressive, as it’s nearly threetimes as long and suggests that polar bears may be even better divers than expected.
Record-Breaking Polar Bear Dive Recorded
The maximum underwater dive duration for a wild polar bear is unknown, in large part because opportunities to document such dives are rare. Researchers studying polar bears in Svalbard (part of the Norwegian archipelagos) got such an opportunity when a hungry “emaciated” polar bear began hunting three bearded seals that were perched on an ice floe (floating ice). According to researchers:1
“The bear dove for a total duration of 3 min 10 s [seconds] and swam 45 to 50 m [meters] without surfacing to breathe or to reorient itself to the locations of the seals. The duration of this dive may be approaching its maximum capability.”
After the “epic” dive, the bear “exploded” out of the water and onto an ice floe. For those wondering, the seal got away but the researchers were still able to capture the whole hunt on video, which confirmed the bear hadn’t come up for air prior to leaping out of the water.
Why the Polar Bear’s Long Dive Is ‘Bittersweet’
The Washington Post described this record-breaking dive as “bittersweet” and “tragic,”2 as it may indicate the bears are resorting to extreme survival measures as climate change leads to less available ice.
Polar bears depend on such ice to hunt, but as the ice disappears they may be rapidly adapting to the changing environment, which necessitates spending more time in the water for “aquatic stalks.” The researchers wrote in Polar Biology:3
“Polar bears diverged from brown bears … about 4[00,000] to 500,000 years ago, which is recent in evolutionary terms. Thus, it is possible that the ability to hold its breath for so long may indicate the initial development of a significant adaptation for living and hunting in its marine environment.
However, increased diving ability cannot evolve rapidly enough to compensate for the increasing difficulty of hunting seals because of the rapidly declining availability of sea ice during the open-water period resulting from climate warming.”
Polar Bears Exhibit Unusual Behaviors As Their Habitat Shrinks
There are fewer than 25,000 polar bears left in the wild, and as their habitat shrinks some other intriguing behaviors have also been observed. A separate team of researchers in Svalbard observed a polar bear eating a dolphin and burying part of it in the snow to eat later.
Not only was the polar bear’s meal choice remarkable (polar bears typically eat seals, not dolphins), but polar bears don’t ordinarily stow away food (the way other bears, like grizzlies, do).4
Polar bears are also spending more time on shore, especially in the summer when sea ice is at its minimum. On shore, the bears resort to eating other foods, like goose eggs and even human trash, which may give them a small nutritional boost but is unlikely to sustain the species as a whole over time. As reported in the journal Frontiers in Ecology and the Environment:5
“Only small numbers of polar bears have been documented consuming terrestrial foods even in modest quantities. Over much of the polar bear's range, limited terrestrial food availability supports only low densities of much smaller, resident brown bears … which use low-quality resources more efficiently and may compete with polar bears in these areas.
Where consumption of terrestrial foods has been documented, polar bear body condition and survival rates have declined even as land use has increased.
Thus far, observed consumption of terrestrial food by polar bears has been insufficient to offset lost ice-based hunting opportunities but can have ecological consequences for other species. Warming-induced loss of sea ice remains the primary threat faced by polar bears.”
How Do Polar Bears Survive in the Arctic Environment?
Polar bears are the only bear classified by most countries as a marine mammal. They’re built to survive on the frozen seas, from their double layer of fur to keep them warm in temperatures that reach -50 degrees F to their thick fat layer (when they’re able to eat enough).
According to Polar Bears International, polar bears are so well suited for the cold that they’re more apt to overheat than to succumb to the freezing temperatures – especially when they run.6
Even polar bears’ feet are covered in fur, as well as papillae, which are small bumps that give them more traction on the ice. Their large front paws, which are slightly webbed, help the bears paddle in the water. Polar bears have even been observed swimming hundreds of miles from shore, although they probably cover a lot of the distance on floating ice sheets.7
Finally, while polar bears are known for their white fur (perfect for providing camouflage when you live in the frozen tundra), their skin underneath it is black, which helps them to absorb warming sunlight.