You might know that polar bears are classed as marine mammals, and also know they can swim, but there isn’t much information on whether black and brown bears can swim.
Polar bears are great swimmers and can swim many miles at a time. Brown bears and black bears can swim, but only when needed.
The bears of North America include the brown bear (Ursus arctos), commonly referred to as the grizzly bear and the black bear (Ursus americanus), the most widely distributed of all bear species.
These two bears are primarily land-bound, however, a very close relative of the brown bear, the polar bear (Ursus maritimus) found in the arctic circle is considered both a land and a water mammal due to its high levels of water occupation, most of which is accumulated hunting on vast sheets of sea ice.
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Can Bears Swim?
Polar bears live in a sub-aquatic habitat and have a high demand for the ability to swim, where brown and black bears, living terrestrially and having a mostly herbivorous diet, swim only when the need arises, such as the very popular salmon spawning season.
This article will answer many of the questions associated with the swimming capabilities of these three species of bears and in some cases, how they differ.
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How Do Bears Swim?
Bears have a similar body shape and physiology to that of dogs and therefore do a similar stroke as the ‘doggy paddle.’ Bears are quadrupeds, meaning they are mobile mostly on all four legs.
The ‘doggy paddle’ stroke primarily uses the front limbs in a paddling motion, while the back legs are used very little. Polar bears have adapted large paws, which are partially webbed to aid in their propulsion through the water, as well as stability while traversing the ice sheets.
The form mentioned above of swimming is energetically very insufficient and can have dire consequences when practiced over long distances (Durner, 2011).
The black bear and the brown bear are less efficient swimmers than the polar bear. Their habitats are much more land-based, and their diets consist mostly of plant materials, seasonal salmon, and sometimes fresh meat or carrion if the opportunity arises.
Polar bears, however, are strictly carnivorous, feeding primarily on seals that use breaks in the ice as breathing or exit holes. A polar bear may dive in and out of the water in the attempt of a sneak attack on a seal, or even, much less often whales that are using breaks in the ice as breathing holes (Alderman, 2018).
Interestingly, A study conducted by Dutch researchers claimed that polar bear/brown bear hybrids, colloquially names’ Grolar Bears’ were better swimmers than brown bears, but not as skilled as polar bears (Preuß, 2009).
Why Do Bears Swim?
Polar bears spend most of their lives on sea ice hunting. In the summer months, the sea ice begins to break apart, leaving large spaces between sheets of ice. Polar bears then need to travel in between these ice sheets to continue hunting. The only way to do that is to swim (National Geographic, 2019). These ice sheets are becoming farther apart as the earth warms, and more sea ice melts, increasing polar bears need to swim.
Brown bears and black bears, with their much more terrestrial habitat, tend to only venture into the water for hunting purposes. One of their main sources of food in the spring season is migrating salmon. The best place for fishing is in the shallow waters of the stream, so very little fishing is required. (Schoen & Gende, 2007).
The brown bears of the commonly named ABC islands of Southeast Alaska have often been seen swimming the channels between islands, and it is believed they do this as different islands vary in the vegetation that is available (Durner, 2011).
Black bears, according to National Park Service, 2019, have also been known to swim just for fun.
How Far Do Bears Swim?
Polar bears are considered marine mammals, as they spend so much time at sea. They have been known to swim hundreds of kilometers between ice sheets. Extraordinarily, Durner et al. recorded one female polar bear swimming a total of 687 kilometers over nine days with only a two day rest in the middle.
It is believed that this extraordinary feat was accomplished over a summer period where the local ice sheets had drifted significantly further apart than normal. This feat did have an unusually large toll on this female with the loss of 22% of her body fat and a yearling cub.
This is an unusually long stint as polar bears generally only swim for up to 10 hours a day before resting. However, speculations are that polar bears will need to swim further and further to travel in between ice sheets. (Oosthoek, 2016)
Brown bears, having been seen swimming across the canals between the ABC islands in Southeast Antarctica, have been known to swim between islands as far as 1.6 kilometers apart. (Durner, 2011).
How Fast Can Bears Swim?
There is very little research available on the speed on which bears can swim. However, there are sources that indicate that polar bears can swim, on average, about 10 kilometers per hour. This may not be completely accurate as the sources did not have citations. In regards to brown and black bear swimming speeds, they have been described as a walking pace by observers.
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Can Bear Cubs Swim?
As polar bears are classified as Marine Mammals, their cubs can swim. However, as experienced in the data recorded by Durner et al., it is apparent that the energetic costs of swimming very large distances are not viable for a young bear.
However, shorter distances between ice sheets are much more viable. Polar bear cubs develop thick waterproof coats soon after hibernation is over.
Black and brown bear cubs, however, are not able to swim until they are around 30 pounds (13.6 kilograms) as stated by Wayne Kaswarm, who is a grizzly bear biologist commenting on a video captured of a mother bear carrying her cubs across a lake on her back (National Geographic, 2019).
Both brown and black bears with cubs tend to give popular fishing grounds a wide birth as their cubs may be put at risk of mortality from bigger or more dominant male bears. This consequently means that they may not be exposed to the opportunity of swimming until later in life. (Durner, 2011).
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So, Can Bears Swim?
The short answer is yes, and very well. However, the details on swimming bears vary greatly among those that inhabit North America. Polar Bears are the gold medalists of swimming, with great distances under their belts and physiological adaptations to assist with these epic journeys.
They may or may not be particularly fast, and are not energy efficient over these long distances. Their cubs do learn to swim early on and are capable of swimming longer distances that even adult bears off the brown and black branches of the family.
Black bears and brown bears have similar swimming habits and behaviors. Although both are adequate swimmers, they choose to only swim much shorter distances of a maximum of several kilometers to get across a lake or from one island to another.
These terrestrial bears enter the water mostly seasonally while fishing for salmon on their way to spawn upstream, and the best fishing spots are in the shallow waters where no swimming is required.
The cubs of brown and black bears are not able to swim until they reach around 13.6 kilograms in weight. Bear cubs are not included in the seasonal salmon fishing events in any case as they may be at risk of death from other bears in a densely populated area.
Bears, in general, are excellent swimmers, although some species are not as strong or enthusiastic as others.
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Durner, G., Whiteman, J., Harlow, H., Amstrup, S., Regehr, E., Ben-David, M. (2010) Consequences of long-distance swimming and travel over deep-water pack ice for a female polar bear during a year of extreme sea ice retreat’, Polar Biol, doi: DOI 10.1007/s00300-010-0953-2 < https://www.fws.gov/r7/fisheries/mmm/polarbear/pdf/Durner_etal_2011_Long_Distance_Swim_Polar_Biology.pdf>
Alderman, S. (2018) Polar bears in action!’, Journal of Experimental Biology, vol 221, no. 7, doi: 10.1242/jeb.169987, < https://jeb.biologists.org/content/221/7/jeb169987>
National Geographic 2019, Brown Bear, National Geographic Partners, retrieved 9 December 2019, < https://www.nationalgeographic.com/animals/mammals/b/brown-bear/>
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National Geographic 2019, American Black Bear, National Geographic Partners, retrieved 9 December 2019, < https://www.nationalgeographic.com/animals/mammals/a/american-black-bear/>
National Geographic 2019, Watch Bear Cubs Hitch a Ride on Their Mom Across a Lake, National Geographic Partners, retrieved 9 December 2019, < https://www.nationalgeographic.com/news/2017/06/bear-cubs-swim-river-alaska-video-spd/>
Yellowstone 2019, Black Bear, National Park Service, retrieved 9 December 2019, < https://www.nps.gov/yell/learn/nature/black-bear.htm>
Oosthoes, S. (2016) Polar Bear Swims for Days as Sea Ice Retreats, Science News for Students, retrieved 9 December 2019, <https://www.sciencenewsforstudents.org/article/polar-bears-swim-days-sea-ice-retreats>
Preuß, A., GünterPurschke, U., Magiera, U (2009) Bear-hybrids: behaviour and phenotypeBärenhybriden: Verhalten und Erscheinungsbild’, Der Zoologische Garten, Volume 78, Issue 4, Pages 204-220, retrieved 9 December 2019 < https://www.sciencedirect.com/science/article/pii/S0044516909000276>