Polar bears and walruses are not only two of the largest marine mammals in the Arctic, but they relate to each other as predator and potential prey in some intriguing ways. At first glance, adult walruses might appear relatively invulnerable to predation, simply because of their sheer size; their thick, heavy skin; their massive, heavy skulls; and, of course, their large, dangerous tusks. Even so, walruses of all ages remain of interest to polar bears simply because there is so much to eat, even on a young animal.

However, walruses are not easy for a polar bear to kill. Even a young calf has a thick, heavy skull that requires multiple bites from a large bear to finally kill it (Figure 1a). Compare this to the single bite to the head from a bear of any size that immediately kills or incapacitates a ringed seal. A subadult walrus may take hours to kill, even by an adult male polar bear (Figure 1b). All of which makes one ask: Which strategy by a polar bear might make preying on a large walrus likely to be successful?

Creative problem-solving

Because of their large brain size, polar bears, like their black and grizzly bear relatives, are thought to be highly intelligent. Furthermore, countless anecdotal accounts of the behavior of all three species suggest they are very clever and creative, especially when the potential for something to eat is involved.

For example, consider how creative a polar bear would need to be to solve the following unnatural opportunity for obtaining food without getting caught. Back in 1971, the late bear biologist, Dr. Charles Jonkel, was using foot snare traps to capture polar bears during the first tagging studies done on the western coast of Hudson Bay near Churchill, Manitoba. One morning, he found the snare at one of the trap sites had been set off without catching the bear … but the bait used to attract it was gone. From tracks in the snow, it appeared that one or more bears had used rocks on the ground beside the trap site to set off the trigger to the foot snare and obtain the bait without being captured. Jonkel then removed the rocks and covered the area around the trap with boards. In response, the bear (or bears) apparently then used rocks—some moved from up to two meters away—to spring the trap and access the food again without being caught.

That anecdote is only one of many about a hungry bear (polar, black, or grizzly) analyzing a novel opportunity to obtain food and then creating an imaginative potential solution on the spot. This inventive part of a bear’s nature is relevant when we consider reports of possible tool use by polar bears, going as far back as 1780 when the famous Danish biologist, Otto Fabricius, reported, based on accounts from Inuit hunters in Greenland, that polar bears were capable of “grabbing pieces of ice and launching them against the walrus’ head … makes it lose its balance and thus kills it easily.”

However, probably the best-known report of possible polar bear tool use is the illustration of a bear on top of a cliff hurling a stone down at an unsuspecting walrus in Charles Francis Hall’s 1865 account of his explorations in Baffin Island (Figure 2).  Hall's Inuk guide and companion told him that, “In August, every fine day, the walrus makes his way to the shore, draws his huge body up on the rocks, and basks in the sun. If this happens near the base of a cliff, the ever-watchful bear takes advantage of the circumstance to attack this formidable game in this way:  The bear mounts the cliff and throws down upon the animal’s head a large rock, calculating the distance and the curve with astonishing accuracy, and thus crushing the thick bullet-proof skull.  If the walrus is not instantly killed—simply stunned—the bear rushes down to the walrus, seizes the rock and hammers away at the head until the skull is broken.”

During the following decades, several explorers and naturalists were told about polar bears in different parts of the Canadian Arctic attacking a walrus by first throwing a piece of ice or a boulder at it. The similarity of this story in the traditional knowledge of different areas makes it difficult to know how many first-hand observations there might have been and how many accounts had been handed down from others. However, in a couple of cases, including the one reported by the renowned Arctic ethnologist, Knud Rasmussen, who was also fluent in Inuktitut, it was reported that the description came from a hunter who claimed to have witnessed it himself. Most recently, a fascinating first-hand account of a polar bear possibly using a piece of ice to help kill a walrus in the late 1990s in Northwest Greenland was given by a highly experienced Inuit hunter in a Traditional Ecological Knowledge (TEK) study led by Dr. Erik Born.

Insights from a zoo bear

When trying to understand a polar bear’s ability to conceptualize a new behavior needed to access a possible food source such as a walrus, consider a young male bear named GoGo in the Municipal Tennoji Zoological Gardens in Osaka, Japan. He was observed inventing and then learning to use tools. Initially, the zoo staff were simply trying to improvise some enrichment to keep him from becoming bored and possibly developing repetitive stereotyped behavior.

First, the staff hung a piece of meat about three meters above GoGo’s pool—which was too high for him to grasp— simply to provide stimulation and distract his attention. Initially he tried to get to the meat by jumping but was unsuccessful.  However, within a month, he had invented two “tools” from toys placed in his exhibit for his entertainment. First, he began to throw a short hard piece of plastic pipe at the meat until he knocked it down (Figure 3a).  Then he picked up the remains of a tree branch to slap the meat off the hook (Figure 3b).  At first, when using either of these methods, it took him a couple of hours to get the meat, according to zoo staff, but soon he was able to retrieve the meat in only five minutes!  Later he began to use a much larger piece of wood (Figure 3c), but as time went on, his preferred tool became a dense object, similar to the initial pipe, which he learned to throw accurately, using both front paws to direct it, much like shooting a basketball (Figure 3d).

Because experienced Inuit hunters are known to be reliable observers of wildlife, their accounts of polar bears using tools to hunt walrus are plausible. This conclusion is supported by the direct observations of GoGo teaching himself to launch a projectile accurately in a totally novel situation.

Dr. Ian Stirling is an adjunct professor with the University of Alberta and a research scientist emeritus with Environment and Climate Change Canada. He is also a long-time scientific advisor to Polar Bears International.

REFERENCES

Born, E.W., Heilmann, A., Kielsen Holm, L., Laidre, K.L. and Iversen, M. 2017. Walruses in West and Northwest Greenland – An interview survey about the catch and the climate. Monographs on Greenland Vol. 355– Man and Society Vol. 44. Museum Tusculanum Press, Copenhagen. 256 pp.

Fabricius, O. 1780. Fauna Groenlandica, pp. 22-24 Ursus maritimus. J.G. Rothe. Hafniae et Lipsiae, xvi+452

Hall, C.F. 1865. Arctic Researches and Life among the Esquimaux being the Narrative of an Expedition in Search of Sir John Franklin in the Years 1860, 1861 and 1862. Harper & Brothers, Publishers. New York, 595 p plus maps. 

Rasmussen, K., 1925. Fra Grønland til Stillehavet. Rejser og Mennesker fra 5. Thule-Expedition 1921-1924 (From Greenland to the Pacific Ocean. Travels and people of the 5th Thule-expedition 1921-1924). Gyldendalske Boghandel. Nordisk Forlag. København 1925. Vol I. 462 p. (In Danish).

Stirling, I., Laidre, K.L., and Born, E.W. 2021. Do Wild Polar Bears (Ursus maritimus) Use Tools When Hunting Walruses (Odobenus rosmarus)? Arctic 74:75–187