Do Wild Polar Bears (<i>Ursus maritimus</i>) Use Tools When Hunting Walruses (<i>Odobenus rosmarus</i>)?

Abstract

Since the late 1700s, reports of polar bears (Ursus maritimus) using tools (i.e., pieces of ice or stones) to kill walruses (Odobenus rosmarus) have been passed on verbally to explorers and naturalists by their Inuit guides, based on local traditional ecological knowledge (TEK) as well as accounts of direct observations or interpretations of tracks in the snow made by the Inuit hunters who reported them. To assess the possibility that polar bears may occasionally use tools to hunt walruses in the wild, we summarize 1) observations described to early explorers and naturalists by Inuit hunters about polar bears using tools, 2) more recent documentation in the literature from Inuit hunters and scientists, and 3) recent observations of a polar bear in a zoo spontaneously using tools to access a novel food source. These observations and previously published experiments on brown bears (Ursus arctos) confirm that, in captivity, polar and brown bears are both capable of conceptualizing the use of a tool to obtain a food source that would otherwise not be accessible. Based on the information from all our sources, this may occasionally also have been the case in the wild. We suggest that possible tool use by polar bears in the wild is infrequent and mainly limited to hunting walruses because of their large size, difficulty to kill, and their possession of potentially lethal weapons for both their own defense and the direct attack of a predator.

Video-documentation of true and borderline tool use by wild American black bears

“…Nonetheless, Bear M48's behavior demonstrated complexity because it required managing dynamic spatial relations (Visalberghi and Fragaszy 2006) between the moving food target and the moving tree sapling. The conceptual creativity that Bear M48 demonstrated by manipulating the tree sapling in attempt to access hanging food was similar to that demonstrated by one captive polar bear who successfully manipulated a branch and a small log as tools to slap hanging meat off a hook (Stirling et al 2021).…”

“…The paucity of research on tool use by wild bears is largely due to the challenge of observing wild bears for extended periods of time (Stirling et al 2021) and the inability to control experiences of wild animals in natural areas (Whitehead 2003). Video cameras offer an alternative method of observing wild bears that does not require researchers to be in the field for extended periods.…”

“…Waroff et al (2017) reported that 6 of 8 captive brown bears ( Ursus arctos ) rolled a log > 2 m, tipped the log onto its flat side, and then stood on the log to reach hanging food. Stirling et al (2021) photo-documented one captive polar bear ( U. maritimus ) using branches, logs, and a round object to slap hanging meat off a hook. To date, the only published observation of tool use by wild bears was reported by Deecke (2012), who video-documented a single wild brown bear using barnacle-encrusted rocks for physical maintenance (i.e., self-scratching).…”