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

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.

Full text

ARCTIC
VOL. 74, NO. 2 (JUNE 20 21) P. 175 – 187
https://doi.org/10.14430/arctic72532
Do Wild Polar Bears (Ursus maritimus) Use Tools
When Hunting Walruses (Odobenus rosmarus)?
Ian Stirling,1,2 Kristin L. Laidre3,4 and Erik W. Born4
(Received 26 October 2020; accepted in revised form 22 December 2020)
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) conrm 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, difculty to kill, and their possession of potentially lethal
weapons for both their own defense and the direct attack of a predator.
Key words: polar bear; Ursus maritimus; walrus; Odobenus rosmarus; tool use; traditional knowledge; TEK
RÉSUMÉ. Depuis la n des années 1700, des signalements d’ours polaires (Ursus maritimus) se servant d’outils (comme
des morceaux de glace ou des pierres) pour tuer des morses (Odobenus rosmarus) ont été communiqués verbalement par
des guides inuits à divers explorateurs et naturalistes. Les guides en question se fondaient sur les connaissances écologiques
traditionnelles (CET) locales de même que sur les interprétations de traces dans la neige ou les récits d’observations directes
des chasseurs inuits ayant fait les signalements. Pour évaluer la possibilité que les ours polaires puissent parfois se servir
d’outils pour chasser les morses en milieu sauvage, nous résumons : 1) les observations décrites aux premiers explorateurs
et naturalistes par les chasseurs inuits au sujet de l’utilisation d’outils par les ours polaires; 2) la documentation récente
attribuable aux chasseurs inuits et aux scientiques; et 3) les récentes observations de l’ours polaire d’un zoo se servant d’outils
spontanément pour avoir accès à une nouvelle source de nourriture. Ces observations, alliées à des expériences publiées
au sujet d’ours br uns (Ursus arctos), permettent de conrmer qu’en captivité, tant les ours br uns que les ours polaires sont
capables de conceptualiser l’utilisation d’un outil pour se procurer de la nourriture qui ne serait autrement pas accessible.
D’après les renseignements prélevés auprès de toutes nos sources, cela aurait aussi pu être occasionnellement le cas en milieu
sauvage. Nous suggérons que l’utilisation possible d’outils par les ours polaires en milieu sauvage n’est pas fréquente et qu’elle
est surtout limitée à la chasse au morse en raison de la grande taille de cette espèce, de la difculté à l’abattre et des armes
potentiellement mortelles qu’elle possède, tant pour se défendre que pour attaquer un prédateur directement.
Mots clés : ours polaire; Ursus maritimus; morse; Odobenus rosmarus; utilisation d’un outil; connaissances traditionnelles;
CET
Traduit pour la revue Arctic par Nicole Giguère.
1 Corresponding author: Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada;
ian.stirling@ualberta.ca
2 Wildlife Research Division, Environment and Climate Change Canada, c/o Department of Biological Sciences, University of
Alberta, Edmonton, Alberta T6G 2E9, Canada
3 Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, Washington 98105, USA
4 Greenland Institute of Natural Resources, PO Box 570, 3900 Nuuk, Greenland
© The Arctic Institute of North America

176 • I. STIRLING et al.
INTRODUCTION
Tool use in the animal kingdom has been the subject of
considerable interest for decades and has been documented
in a wide variety of species ranging from insects to
mammals (see reviews by Alcock, 1972; St Amant and
Horton, 2008; Bentley-Condit and Smith, 2010; Shumaker
et al., 2011). In their extensive review, Bentley-Condit and
Smith (2010) created 10 separate categories within which
to classify documentation of tool use, including whether a
particular observation was anecdotal, only seen in captivity,
or only observed in one subject. They did not indicate
whether or how the individual categorizations might
inuence the overall assessment of the relative signicance
of such observations. Basically however, most researchers
agree that the denition of “tool use” simply constitutes the
use of a freely manipulatable object to modify the physical
properties of a target object through a complex mechanical
interaction (Deecke, 2012).
It is widely accepted that bears (Ursidae) as a group
are intelligent, in part because of their large brain size
(Holecamp and Benson-Amram, 2017) but also because of
a range of sophisticated hunting strategies and behavioral
interactions (e.g., hunting strategies in polar bears, Ursus
maritimus; Stirling, 1974; Stirling and van Meurs, 2015).
However, in their literature review of tool use, Bentley-
Condit and Smith (2010) reported only one observation
from Kiliaan (1974) of possible tool use by a polar bear
(a second citation in their paper of Stirling [1974] is
incorrect as there is no mention of tool use in that paper).
One interpretation of the paucity of observations on bears
in their study might simply be that, as a taxonomic group,
bear species use tools less often. However, the paucity of
observations may partially result from the difculty of
making extended observations of the behavior of wild
bears and does not preclude the possibility that bears might
infrequently use tools only on an “as needed” basis. Also, to
some degree, it likely reects a general lack of experimental
studies of the abilities of captive species of bears to solve
different kinds of problems in captive situations.
Since publication of the broad reviews of tool use
referred to above, several recent studies conducted under
experimental conditions have confirmed the presence
of special and cognitive abilities in captive giant pandas
(Ailuropoda melanoleuca), American black bears (Ursus
americanus), Bornean sun bears (Helarctos malayanus
uryspilus), and Indian sloth bears (Melursus ursinus)
(Perdue et al., 2009; Vonk and Beran, 2012; Vonk et al.,
2012; Zamisch and Vonk, 2012; Perdue, 2016; Amici et al.,
2017, 2019; Hartmann et al., 2017). Of particular relevance
to this study are the experimental demonstration of tool use
by captive brown bears (Ursus arctos) (Waroff et al., 2017)
and a similar experiment with captive Indian sloth bears
(Amici et al., 2019) in which the subjects were unsuccessful
at demonstrating similar abilities.
For polar bears, there is a consistent historical record
in Inuit traditional ecological knowledge (TEK), reported
verbally to several early explorers and naturalists. In this
paper, we use the term TEK as dened by Berkes (2012:7):
“A cumulative body of knowledge, practice, and belief,
evolving by adaptive processes and handed down through
generations by cultural transmission, about the relationship
of living beings (including humans) with one another and
with their environment.” A closely related term is local
ecological knowledge (LEK). Some researchers have
taken the view that LEK is a subset of TEK and presents
“current local knowledge acquired more recently over the
lifetime of individuals” (Gilchrist et al., 2005:22; Henri et
al., 2018). For the purposes of this paper we use the term
TEK to include all information sourced from Inuit hunters
in historical as well as recent times.
Since 1780 (Fabricius, 1780), reports of polar bears
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 Inuit TEK, and in some cases, based on direct
observations or interpretations of tracks in the snow.
Although some writers appear to have considered such
reports as myths (e.g., Ellis, 2009) because of the absence
of published reports based on conventionally veriable
documentation (i.e., peer-reviewed scientic publications),
the persistence of such similar accounts from a diversity
of locations and over a long period of time suggests that a
more detailed overall review of the subject is warranted.
Thus, we summarize both historical information and recent
observations from all sources on the behavior of both wild
and captive polar bears using tools to access food.
METHODS
We summarize all available information that we were
able to access and conrm on possible tool use by polar
bears in three parts. First, we review and summarize
historical reports of tool use by polar bears as reported
by Inuit hunters to early explorers and naturalists in two
categories—secondhand TEK accounts and descriptions
reported as having been observed by the hunter reporting
them. We then summarize details of recent observations
of tool use reported in the literature by Inuit and non-Inuit.
Finally, we document recent observations of tool use by a
captive male polar bear in the Tennoiji Zoo in Osaka, Japan,
and by captive brown bears, their closest ursid relative, in
an experimental study in the State of Washington, USA.
Using our own cumulative and extensive scientific
knowledge of the behavior and ecology of both polar bears
and walruses, the history of Arctic exploration, and TEK
publications that include aspects of hunting of polar bears
and marine mammals by Inuit in the marine ecosystem,
we focused on 1) books and reports written by explorers
or scientists who had been active in the Arctic from the
19th century through the rst half of the 20th century,
especially those who had remained in areas frequented
by both polar bears and walruses for extended periods of

TOOL USE BY POLAR BEARS HUNTING WALRUSES • 177
time and had frequent contact with Inuit hunters; and 2)
published TEK and scientic reports from recent decades
that included aspects of polar bears hunting walruses and
seals. We searched the polar collections of the University
of Alberta Library (Edmonton) and the Danish Royal
Library (Copenhagen; including some sources in Danish,
German, and Swedish). In both those institutions, we were
aided by competent and motivated librarians. Searching
the internet and the Web of Science for papers that listed
both polar bears and walruses in the key words revealed no
relevant references that we were not already aware of. Ian
Gjertz, a former employee of the Norwegian Polar Institute
and the Norwegian Natural Science Foundation, searched
both published and unpublished sources (e.g., journals of
Norwegian trappers and hunters living in Svalbard and East
Greenland) for records of polar bears using tools but found
none. Lastly, we consulted widely with colleagues who had
signicant personal experience in both scientic and TEK
research collaboration with Inuit groups in areas where the
distributions of polar bears and walruses overlap and who
had knowledge of unpublished TEK reports from various
administrative agencies. There may be additional TEK
held by Inuit hunters that was not reported to explorers in
historical times or those conducting TEK studies in more
recent times. However, the extensive nature of our search
and the internal consistency of the content of the events
reported suggest to us that our coverage of the available
information is comprehensive.
RESULTS
Within Inuit TEK from both the eastern Canadian Arctic
and SW Greenland, there is a long oral history dating back
more than 240 years of bears using blocks of ice or stones
(i.e., “tools”) to aid in killing walruses. It is unclear whether
all the reports are of independent observations or whether
there might also be some overlap resulting from similar
TEK being passed down over generations or to different
areas. However, it was not possible to assess the uniqueness
of some observations so we tabulated all reports separately
under the following categories: secondhand accounts from
non-attributed TEK sources, rsthand accounts from Inuit
hunters, and direct observations reported by those who
published them.
Secondhand Accounts from TEK
1. In Fauna Groenlandica, Fabricius (1780:22 – 24)
who lived in SW Greenland from 1768 to 1773 (as a
clergyman and naturalist) reported that, “It [the polar
bear] attacks every living creature, especially seals
and the walrus. Cunning makes up for its lack of force
against the mighty tusks of the latter. Grabbing pieces
of ice and launching them against the walrus’ head,
the bear makes it lose its balance [or “stagger” is more
literal] and thus kills it easily. However, sometimes it
is bested by the walrus, or both of them die from their
wounds.” (Translated from the original Latin document
by L.M. Stirling, University of Manitoba).
2. Probably the best-known account of polar bear tool use
is the one illustrated by the engraving in Hall (1865:581)
of a polar bear on top of a cliff hurling a stone down at
an unsuspecting walrus (Fig. 1). Hall’s Inuk guide and
companion from SE Bafn Island told him that, “In
August, every ne day, the walrus makes his way to the
shore, draws his huge body up on the rocks, and basks in
the sun. If this happen [sic] 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 till the
skull is broken.”
3. Munn (1932:242) reported the following but provided no
additional detail: “The natives of different tribes widely
separated have told me they have watched a bear stalk
a young walrus out on the ice, taking advantage of a
hummock to get within striking distance, and then hit
the walrus over the head with a piece of ice held in one
paw.” Munn accumulated his information during several
years working closely with Inuit in Arctic Canada
including SE and NE Bafn Island and Southampton
Island in Hudson Bay, Nunavut, Canada, all of which
have resident walrus populations (e.g., Born et al., 1995).
FIG. 1. This illustration, titled “Bear killing walrus” (Hall, 1865:581), depicts
the use of a rock as a tool to try to kill a walrus, as described to the explorer
Charles Francis Hall by a local Inuk hunter.

178 • I. STIRLING et al.
4. In a posthumously published account, Haig-Thomas
(1956) reported being told by an unidentied Inuk hunter
that “long ago some Eskimos saw a herd of walruses
sleeping on the ice and a polar bear approaching them.
When the bear was close he lifted a large boulder of ice
and dashed it down on the head of one of the walruses.
This story I believe is told all over Greenland and the
Canadian Arctic.” In another anonymous account, he
was told “An Eskimo killed a walrus with skin hanging
from its skull. When he had pulled it up on to the ice
and examined the wound carefully he thought that a bear
must have tried to kill it with a large boulder and had
only struck it a glancing blow, scraping the skin off the
skull, though this might have occurred by ice falling off
a glacier. If, however, one does not accept this account,
it is difcult to see how a bear could kill a large walrus
before it got into the sea.”
5. Perry (1966) reported that, “Within our own times,
a Southampton Island Eskimo, Tonga by name, has
declared that he drove off a bear that had killed a sleeping
walrus in this way [by hitting it on the head with a piece
of ice], and that he subsequently butchered the walrus’s
carcass.” However, his information was secondhand, and
we have been unable to conrm the source.
6. In a recent unpublished interview as part of a TEK study
relating to polar bears in Arctic Bay, Nunavut, P. Wong,
Trailmark Systems, Toronto, Canada (pers. comm.
2020) recorded the following from an Inuk hunter from
Arctic Bay in reference to polar bears hunting walruses:
“They’re [polar bears] the only species we know, that
can think…that can have weapon. Like, we know that
they can design a…piece of ice, make it round, they
can use that to smash walrus head…for instance. They
can think, when they’re pursuing a prey, like humans”
(AB15, anonymous identication of Interviewee).
Inuit Hunter Accounts
We dene rsthand accounts as ones given by an Inuk
hunter who could be identied by name and where he lived
and who said he had personally witnessed a polar bear
using a tool to kill a walrus.
1. While his ship was frozen in for the winter in Foxe Basin,
Nunavut, Lyon (1824:375 – 376) shared his cabin with
an Inuk hunter named Ooyarra. During that time, the
hunter told him that, “On one occasion he saw a bear
swim cautiously to a large piece of rough ice, on which
two female walruses were lying asleep with their cubs.
The wily animal crept up some hummocks behind this
party, and with his forefeet loosened a large block of ice;
this, with the help of his nose and paws, he rolled and
carried until immediately over the heads of the sleepers,
when he let it fall on one of the old animals, which was
instantly killed. The other walrus with its cub rolled
into the water, but the young one of the stricken female
remained by its dam; on this helpless creature the bear
now leaped down, and thus completed the destruction of
two animals which it would not have ventured to attack
op e nly.”
2. Rae (1883) reported the following hunt of a walrus
by a polar bear, reported to him by “an eye witness, a
very truthful and honest Eskimo” who claimed to have
witnessed the event on drifting ice in Foxe Channel, east
of Southampton Island. A swimming bear climbed out
on the ice that three walruses were sleeping on and “I
and two or three other Innuits [sic] were attempting to
approach some walrus in winter, lying on the ice close
to the water kept open by the strong current in Foxe’s
Channel. As we were getting near we saw that a large
white bear was before us. He had reached, in the most
stealthy manner, a high ridge of ice, immediately above
where the walrus was lying. He then seized a mass of
ice in his paws, reared himself on his hind legs, and
threw the ice with great force on the head of a half-
grown walrus, and then sprang down upon it.” After the
bear was killed with a spear, the walrus was found to be
almost dead.
3. Rasmussen (1925:81 – 82) was in the Igloolik area in
northern Foxe Basin, where the angakok (shaman) Aua
told him that he had once seen a polar bear sneaking
up to a group of walruses. It had a massive lump of ice
between its forepaws and hid itself behind this piece
of ice so that its yellowish body was never detected by
the walruses. If the walruses moved, the bear remained
completely motionless looking like the hummocky sea
ice. However, the walruses had hardly calmed down
before it started to creep towards them again—raised
up on its hindlimbs. Then it nally carefully selected a
young walrus and threw the ice block down upon it with
such a force that it became immobilized while all the
other group members moved into the water. (Translated
from the original Danish by E.W. Born).
4. Nelson (1969:191) was told by an unnamed hunter from
Ulguniq (Wainwright, Alaska) that he saw a polar bear
approach some walruses sleeping on the ice and try to
attack a calf but the adults would not leave it. The bear
then picked up a chunk of ice (or several chunks) with
both paws, stood up on its hind legs, and threw it at the
walruses in a vain attempt to drive them away from
the calf. In a summary statement, Nelson reported
that, “Walrus hunting [in Alaska] by bears is often said
to involve pieces of ice and rock,” but no additional
observational information was provided.
Lastly, for the last century, after the introduction of
skiffs and larger vessels in the subsistence walrus hunt in
Canada and Greenland, the majority of the annual catch of
walruses has been taken in offshore pack ice (e.g., Born et

TOOL USE BY POLAR BEARS HUNTING WALRUSES • 179
al., 1995, 2017) where the distribution of walruses and polar
bears overlap. In several instances the hunt targets both
species (Born et al., 2017). However, despite an apparently
increasing opportunity to observe interactions between
the two species in their natural habitat, reports from Inuit
hunters of polar bears using tools to kill walruses are very
few. The small number of reports suggests to us that the use
by polar bears of tools to kill walruses is an unusual event.
Published Direct Observations
1. In April 1972, Kiliaan (1974) was sledging with two
Inuit hunters across Sverdrup Inlet on Devon Island,
Nunavut, conducting a denning survey, when one hunter
reported having just observed a place where a polar bear
had smashed in the snow roof over a ringed seal (Pusa
hispida) aglu (breathing hole) with a piece of ice. An
inspection of the site revealed a piece of freshwater ice,
approximately 20 kg in weight and 80 cm long, lying at
the edge of the snow cover that had been dug away from
the aglu. From tracks that were estimated to be about
6 h old, it was determined that the bear had broken the
ice block from a larger piece of frozen-in freshwater ice
about 6.5 m away and that it appeared to have dragged
the ice block to the dig site. In the end, they were unable
to conrm exactly what happened but suggested three
possibilities: the bear used the ice block to break through
the rm snow cover overlying the aglu, it had used the
ice block to try to kill a seal that surfaced to breathe or,
after being unsuccessful, it had broken the piece of ice
off in frustration and rolled it to the site of the aglu.
2. Kiliaan (1974) also cited a personal communication
observation of possible tool use by one or more polar
bears by the late bear biologist, Charles Jonkel,
University of Montana. In 1971, Jonkel was using foot-
snare traps to capture polar bears for tagging studies
on the western coast of Hudson Bay near Churchill,
Manitoba. From tracks in the snow, it appeared that one
or more bears had used rocks beside a trap site to set the
foot snare off in order to obtain the bait without being
captured. After Jonkel removed the rocks and covered
the area around the trap with boards, the bear (or bears)
apparently used rocks from up to 2 m away to spring the
trap again and access the food.
3. Born et al. (2011:88) reported an interview for a TEK
study about polar bears in NW Greenland, in which
a 44-year-old highly experienced Inuk hunter from
Qaanaaq (Ingleeld Bredning, NW Greenland) reported
his personal observation of possible tool use. For this
paper, the hunter’s original account, recorded on tape in
Greenlandic and transcribed into Danish, was further
checked and edited by E.W. Born. In the late 1990s, the
hunter was returning from hunting in the Kane Basin (a
body of water between Ellesmere Island, Canada, and
NW Greenland) region with two companions during a
very cold period in late February or early March. He saw
two walruses on the ice (at about 78.347˚ N, 72.685˚ W)
and approached them with the intention of harvesting
one for dog food. When he got closer he saw blood on the
ice from a female walrus that a bear had just killed. He
put his nger on the bear’s urine in the snow and found
it unfrozen, indicating it was still very fresh. He thought
that the bear got nervous when it heard him approaching
by dogsled and urinated before running away. It was
clear that the bear had killed the walrus. However, from
the fresh tracks in the snow, it appeared that before the
bear sat down to wait for the walrus to return to the
breathing hole, the bear had fetched a piece of saltwater
ice from the nearby coastal tide crack (estimated size not
specied) and had manipulated it until it was smooth all
over its surface. The manipulations were not described.
The bear then had a tool with which to kill the walrus
with a blow to its head. The bear then sat on some frozen
bergy bits and when the walrus surfaced to breathe it
had leapt towards it, leaving deep scratches in the new
ice with its claws. On examination of these observations
with his two companions, he concluded that the bear
had attacked the walrus and hit it on the head with its
weapon (the ice block). The blow had smashed its skull
from a little above the upper lip all the way to the back
of its head. The skull had been hit so hard that the skin
was torn open. After the bear had hauled the walrus out
of the water, it had dragged it some distance from the
breathing hole where it had surfaced. The walrus was
reported to be an old pregnant female with nice tusks.
In a separate interview (Born, 2011:490), but related
to the rst because both referred to manipulation of the
shape of an ice piece by a polar bear, the same hunter
“reported having observed the tracks of two small
cubs with their mother in the vicinity of Sermersuaq
(Humboldt Glacier in NW Greenland) in April during
the 1990s. Their mother had made a ball for them out of
a piece of saltwater ice, which she had taken from the
area between an iceberg and the sea ice. The ice ball
was completely spherical and approximately twice the
size of a soccer ball (ca. 45 cm in diameter). The hunter
described it as follows: “If mathematicians had measured
it, they would be amazed at how perfectly round it was.”
The bear cubs played with the ball (and had slid down
the iceberg for a long time). According to the hunter, the
ball was probably made of sea ice in order to make it
more solid than if it had been fashioned out of freshwater
ice from the iceberg, which would have been more
brittle and would have broken more easily. It was smooth
and rounded so that it would not crack and was, in the
hunter’s opinion, an implement devised and fashioned by
a polar bear (Born et al., 2011).
4. In 2010, a journalist (Hiroyuki Ueba, pers. comm. 2010)
with the Yomiuri Shimbun newspaper in Osaka, Japan,
sent photographs to the senior author of a 5-year-old
male polar bear named GoGo (originally from a zoo in

180 • I. STIRLING et al.
FIG. 2. Five-year-old GoGo, a male polar bear in Tennoji Zoological Gardens, Osaka, Japan, using tools to access a food source suspended above his reach.
Panels show GoGo (a) throwing a piece of plastic pipe, (b) holding a 2 m piece of tree branch, (c) using a small log and, (d) throwing a small dense buoy-shaped
tool using both forepaws at the same time (Photos © Tennoji Zoological Gardens, Osaka, Japan).

TOOL USE BY POLAR BEARS HUNTING WALRUSES • 181
Russia) at the Tennoji Zoo in Osaka. In these photos,
GoGo demonstrated an exceptional and previously
undocumented degree of conceptual creativity to
facilitate access to a food item hanging from the air
(Stirling, 2011:148). The circumstances that led to the
bear beginning to use tools, as described below, were
not part of a planned experiment; unfortunately, no
written records of observations were made at the time
or since. Thus, the following brief notes are based on
the recollections of the Animal Coordinator for the
zoo (Takahiko Ide, pers. comm. 2019) of the initial
development of GoGo’s behavior and its continuation
over a 10-year period. Initially, zoo staff had been trying
to improvise forms of behavioural enrichment to keep
the bear from becoming bored and possibly developing
repetitive stereotyped behavior. Thus, to provide
stimulation and distract his attention, they hung a piece
of meat about 3 m above his pool, which was too high for
him to grasp. Initially GoGo tried to get to the meat by
jumping but was unsuccessful. However, about a month
later, the bear invented two tools from “toys” originally
placed in his cage for his entertainment. First, he began
to throw a short, hard piece of plastic pipe at the meat
until he knocked it down (Fig. 2a). Second, although
it is not known exactly how much later, he picked up
the remains of a tree branch, about 2 m long, and used
it to slap the meat off the hook (Fig. 2b). When he rst
developed these methods, it took him a “couple of hours”
to get the meat by using either technique but after a while
his skills improved and he was able to retrieve the meat
in only 5 minutes. He later began to use a much larger
piece of wood (Fig. 2c), which he apparently preferred
when both wood pieces were available, although the
possible reason was not clear. As time went on however,
he continued to prefer to throw things at the meat and
ultimately stopped using the pieces of wood. At the time
of this writing, after about 10 years, his preferred tool
is a hard, dense, circular, and negatively buoyant buoy-
shaped object, similar in size to the initial pipe, which
he throws very accurately at the meat target, using both
front paws to direct it, much like shooting a basketball
(Fig. 2d). In 2019, a meat bait was suspended at a similar
height above a 6-year-old female bear (also from a
Russian zoo and raised in captivity) named Icchan. She
has not been able to observe GoGo using tools. Although
she sometimes threw a buoy, a tire, and a basket into her
pool and then dove in for them, so far she has not tried
to use any of the objects as tools to obtain the suspended
food.
DISCUSSION
TEK Historical Perspective of Polar Bear Tool Use
Over a period of at least 240 years, there is a striking
recurrence of highly similar but independently reported
accounts given by Inuit hunters to early explorers and
naturalists visiting SW and NW Greenland and the eastern
Canadian Arctic of polar bears using pieces of ice or (in
one case) stones as tools to kill walruses, as well as one
similar record from Alaska (Nelson, 1969). Conversely,
in other areas where large numbers of walruses and polar
bears also overlap in distribution, there have been no TEK
accounts or direct observations made by local Indigenous
hunters in Chukotka, Russia, or by foreign hunters or
trappers in Svalbard, Norway, of tool use by polar bears
hunting walruses that we are aware of despite considerable
eld research, documentation of TEK, and hunting of both
species (e.g., Ovsyanikov, 1996; Kochnev et al., 2003, pers.
comm. 2020; Øren et al., 2018; I. Gjertz, pers. comm. 2020).
While reports of polar bears using ice blocks or rocks
to kill walruses have been known for some time, there
has not been any previous attempt to collate and assess
these observations collected over the past 200+ years.
Some writers (e.g., Ellis, 2009:97) simply concluded that
the stories were mythological while, in contrast, Nelson
(1969:191) noted that “Most authors have questioned
whether this [tool use] occurs, however, apparently doubting
that the hunters are able to view their own surroundings
objectively. Yet it is worth remembering that Eskimos are
highly reliable observers of animal behavior, and many of
their least believable statements have been proved to me by
personal observation.”
As eld scientists, our personal experience over several
decades of working with Inuit hunters in Canada and
Greenland is that that reports of direct observations of
wild animals by experienced individual Inuit hunters are
highly reliable. The statement above by Nelson (1969) is
particularly relevant in relation to the detailed observation
reported personally by a highly experienced polar bear
and walrus hunter in NW Greenland (Born et al., 2011:88).
He and two companions interpreted exceptionally fresh
tracks, apparently made immediately before their arrival at
the site, to determine that a polar bear had killed a walrus
by using a piece of ice (Born et al., 2011:88). We suggest
that the interpretation of the recent observation of this
highly experienced Greenland hunter should be considered
plausible, as should the longer-term historical record of
similar observations.
Tool Use by Captive Brown Bears and Polar Bears
The closest living relative of the polar bear is the
brown bear, from which the former evolved about half a
million years ago (Liu et al., 2014). There are two recent
reports in the literature of tool use by brown bears. In
the rst, Deeke (2017) observed a brown bear on a single
occasion repeatedly pick up barnacle-encrusted rocks in
shallow water, reorient them in its forepaws, and use them
to rub its neck and muzzle. The purpose of this behavior
was not apparent, which weakens the interpretation.
Although feeding by brown bears in salmon streams has
been observed extensively in several situations for many

182 • I. STIRLING et al.
years (e.g., Shardlow and Hyatt, 2013; Lincoln and Quinn,
2019), no observations of tool use in that or other feeding
circumstances have been reported.
In the second, a unique controlled experiment (Waroff et
al., 2017) demonstrated that six of eight captive brown bears
taught themselves to use three previously unfamiliar objects
(large log, small log, and box) as tools to access a food
reward suspended too high to be reached without moving one
of the objects to a position below the food and then standing
on it in order to be able to reach it. Successful individuals
exhibited different preferences for tools and techniques but
all were able to independently use a new and unfamiliar tool
in a similar manner. Because the two bears that did not learn
to use tools were both born and lived in the wild prior to
being in captivity, Waroff et al. (2017) suggested that having
been raised in captivity may have contributed to the ability of
six of the bears to learn to use tools.
It is difcult to compare the observations of tool use
by six of the eight brown bears in controlled experimental
conditions to those of GoGo, the ve-year-old captive male
polar bear in the Tennoji Zoo in Osaka, because of the
limited and anecdotal nature of the descriptions of tool use
by the latter. However, similar to the brown bears, once
GoGo was successful at using the rst tool to access the
food suspended out of his reach, he recognized that new
and unfamiliar tools might also be used to accomplish the
same task. Additionally, when all his tools were available
to him at the same time, he showed preferences and, in
his continuing use of tools through the past decade, has
apparently developed a particular afnity for a small, dense,
and negatively buoyant buoy-shaped tool that he throws
with considerable accuracy with both paws (Fig. 2d).
Despite the fact the observations of GoGo were qualitative,
it is clear that he was capable of independently solving the
problem of accessing a food source he could not reach in
any other way than by using a tool. Furthermore, he was
able to apply more than one type of tool to solve the same
problem and retained the ability to apply the behavior over
a period of 10 years. To date, however, although having
been raised in captivity like GoGo, the 6-year-old female
polar bear (Icchan) has not yet been able to use a tool to
access the meat bait, rst suspended above her pen in a
similar fashion in 2019.
In contrast to evidence from captive polar and brown
bears, Amici et al. (2019) experimentally demonstrated
that captive sloth bears were unable to recognize that they
could access an out-of-reach food source by simply moving
a familiar bucket and standing on it (see also Waroff et al.,
2017). Despite behavior that they interpreted as indicating
high motivation, and in contrast to their predictions, Amici
et al. (2019) found that none of the sloth bears tested tried
to access the food by standing on the bucket, even after
they either observed a human experimenter modeling the
behavior or after being given direct relevant experience
about how to reach the goal. The authors suggested that
sloth bears failed to cognitively recognize the problem and
use available tools to solve it.
Ecological Context of Possible Tool Use
The diversity of TEK reports of polar bears using ice
blocks or rocks as tools with which to successfully kill
prey all involved hunting walruses. The body mass of adult
walruses is on average about three times larger than that
of polar bears (Knutsen and Born, 1994; Wiig and Gjertz,
1996; Derocher and Wiig, 2002) and walruses are usually
found in groups of variable size (Born et al., 1995; Stewart
et al., 2014). Furthermore, walruses have 2 – 4 cm of thick
skin on the head and neck (Fay, 1982) that is difcult to
tear even with a sharp knife (E. Born, pers. observ.) and
likely also with sharp canines, plus a dense skull (Kastelein
and Gerrits, 1990) that can withstand blows or attempts to
penetrate the braincase by a bear biting it with its canine
teeth. In addition, walruses are armed with tusks that are
formidable weapons and probably sufcient to protect
adults from polar bears in most situations (Fay, 1982). Not
surprisingly, the majority of published reports of polar
bears hunting walruses reported in the literature suggest
their primary focus is on calves and younger (smaller)
animals, although adult animals are occasionally killed
as well (Loughrey, 1959; Kiliaan and Stirling, 1978; Fay,
1982; Calvert and Stirling, 1990; Øren et al., 2018; Miller
and Kochnev, 2021). However, even small walruses have
large, heavily constructed skulls (Kastelein and Gerrits,
1990) as well as thick skin on the head and neck so that,
in most cases, even killing a calf would require multiple
bites (Fig. 3a) and probably blows to the head with the
front paws as a polar bear’s bite is not capable of crushing
the skull and brain. Similarly, because of their relatively
impenetrable skulls, even smaller subadult walruses may
require an extended period to kill (e.g., Fig. 3b) compared to
a ringed seal which may be quickly dispatched with a single
bite, although multiple bites usually follow, presumably to
eliminate the chance of it recovering sufciently to escape
(I. Stirling, unpubl. observ.). It is also apparent from tracks
and blood in the snow near breathing holes that some
walruses have escaped after being attacked (e.g., Calvert
and Stirling, 1990) and, some cases, it appears that the
bear may even be killed by the walrus (Freuchen, 1935;
Pedersen, 1962; Kiliaan and Stirling, 1978). Stirling (1984)
also documented a group threat behavior by walruses in
the water to a bear hunting walruses along the ice edge in
a polynya, sufcient to cause the bear to run from the ice
edge and leave the area quickly, which further illustrates
the possible direct danger to a polar bear when hunting
walruses. The possible risk of harm to a bear from attacking
a walrus was also rst reported by Fabricius (1780).
Recognizing the ongoing difculties that wild polar
bears experience when hunting walruses (a substantial
but dangerous food source) suggests the possibility that a
small number of individuals might make the conceptual
mental link between the need for a potential tool that
might facilitate an improvement of hunting success and a
possible solution. It is in this context that the observations
of GoGo, the polar bear in the Tennoji Zoo in Osaka,

TOOL USE BY POLAR BEARS HUNTING WALRUSES • 183
FIG. 3. (a) head of a walrus calf killed by a polar bear illustrating multiple bites from a polar bear attack without breaking the skull (photo © M.K. Taylor) and (b)
a bloody ongoing attack by a polar bear on a subadult walr us that illust rates the bear’s inability to kill the walrus quickly by biting its head (photo © Rod Vallee).

184 • I. STIRLING et al.
may be most relevant. Clearly, polar bears are intelligent
animals and are able to quickly learn to perform tasks
for research purposes (e.g., Øritsland et al., 1976) or in
circus situations (e.g., Engelhard, 2017) that relate to no
obvious function in the wild. No training or deliberate
experimental designs were used to stimulate or test GoGo’s
potential abilities. However, in captivity, with free time
and few other distractions, GoGo’s desire to access the
meat was apparently sufciently strong for his brain to
somehow conceptualize using a tool to successfully knock
the bait down. Furthermore, after success and positive
reinforcement from use of the rst tool (a piece of plastic
pipe), he then conceptualized the use of a second quite
different tool (a 2 m long stick) to similarly access the meat
that had been deliberately suspended on a hook beyond his
reach. Lastly, and of particular importance with respect to
whether a polar bear might be able to use a tool to kill or at
least partially disable a wild walrus, GoGo demonstrated a
remarkable ability to conceptualize the use of a tool to solve
an access problem and, importantly, to be able to coordinate
the use of both forepaws to throw his tool at least 2 m
with considerable accuracy. The ability of polar bears to
conceptualize how to solve a problem to access food with a
tool is further illustrated by the non-hunting example of the
polar bear that used a rock to set off a foot snare so it could
get the bait without being caught (C. Jonkel, cited pers.
comm. in Kiliaan, 1974).
When hunting for ringed seals at their lairs or agluit
(breathing holes) beneath the windblown snow in spring,
polar bears must stand completely motionless over the
site, in order to not make even a tiny noise that would
immediately frighten a seal in the water below. To have
any chance of success, the bear must remain absolutely
motionless, usually for an extended period, prior to a
seal possibly surfacing to breathe at an aglu and being
vulnerable to attack. Even the noise created by a small
movement needed to pick up or move an ice block as a tool
is sufcient to warn a seal to ee instantly well before an
attack could be initiated. Thus, it seems unlikely that the
polar bear tracks described by Kiliaan (1974) around a
ringed seal aglu were made by a bear trying to use a tool
to hunt a ringed seal beneath the snow. Consequently,
because agluit or haulout and birth lairs are protected by
a covering of windblown snow (Smith and Stirling, 1975;
Stirling and Øritsland, 1995), the ongoing lack of success of
tool use in that circumstance would likely result in negative
reinforcement.
In the case of the captive brown bears, it is impressive
that the intensity of the motivation to access a small food
item suspended beyond their reach was sufficient to
stimulate six of the eight individuals to independently
conceptualize using the same tools in different ways to
solve the problem of how to access the bait (Waroff et al.,
2017). Even more interesting was that each bear exhibited
alternative techniques and displacing of tools (log, stump
or box) to facilitate being able to reach for the food reward.
In stage three of the study, four of the six bears also chose
to use novel objects that were not present in earlier stages of
the experiment, which indicates the presence of a problem-
solving concept rather than simply a rote memory of what
had been done before. Similar to the use of different tools
by GoGo, Waroff et al. (2017) further suggested that “This
capacity to use different tools for the same purpose is
suggestive of an elaborated cognitive understanding of the
environment.” In a possible parallel to GoGo’s experience,
part of the explanation for the brown bears’ ability to
invent a tool may have been that being in captivity with
few distractions, possibly bored, and with an abundance
of time to contemplate the problem, made it possible for all
six bears to independently conceptualize solutions from the
potential tools available at the time.
Why the two brown bears that were brought into
captivity from the wild did not successfully use a tool to
access the suspended bait in a similar manner to the six
bears raised in captivity is uncertain. However, there have
been no known observations of wild brown bears using any
kind of tool similar to the TEK reports on wild polar bears.
One possible explanation may simply be that there are not
any known situations where a possible tool might improve
the success of feeding on primary food sources such as
vegetation, spawning sh, or newborn ungulate calves.
Thus, the bears that were brought into captivity from the
wild probably had no early experience with having a need
for access to a food source that might be strong enough to
stimulate possible use of a tool to achieve success.
SUMMARY
The detailed experimental observations of tool use by
captive brown bears, when considered in relation to the
non-quantitative but clear descriptive and photographic
record of tool use by the captive polar bear, GoGo, indicates
that both of these closely related species of bears are
capable of independently conceptualizing the successful
use of tools to resolve access to a unique food-related
problem. The documentation of a wild polar bear using a
rock to harmlessly set off a foot snare also suggests it may
have been captured at an earlier time and, consequently,
was also able to conceptualize a solution to the threat of
being recaptured and thereby be rewarded with access to
the bait. Taken together, these observations, along with
GoGo’s ability to access a bait suspended out of his reach
by coordinating the use of both front paws to throw a tool
accurately and thus determine its trajectory, leave us to
speculate that an occasional adult polar bear might be
capable of mentally conceptualizing a similar use of a piece
of ice or a stone as a tool to attack the well-protected brain
of a walrus in order to kill it. The long history of similar
observations reported from the wild by Inuit hunters, when
combined with the observations of captive polar and brown
bears, suggests the former may also have the ability to
conceptualize the possible use of tools in the wild.

TOOL USE BY POLAR BEARS HUNTING WALRUSES • 185
Lastly, the mention of both an adult male polar bear and
an adult female with cubs having similarly modied the
shape of a block of saltwater ice further suggests, albeit
more speculatively, the possibility that the creation and
use of a tool might be taught and transmitted between
generations. Consequently, we suggest that although tool
use by polar bears in the wild is likely a rare event, their
possible use would likely be limited to walruses because
of their large size, difculty to kill, and their possession of
potentially lethal weapons for both their own defense and to
directly attack a predator.
ACKNOWLEDGEMENTS
We thank the Wildlife Research Division of Environment and
Climate Change Canada, the University of Alberta Department
of Biological Sciences, Polar Continental Shelf Project, Natural
Sciences and Engineering Research Council (Ottawa), the
Greenland Institute of Natural Resources, the Environmental
Ministry of Denmark (DANCEA), and the Government of
Greenland for long-term support of our research. We are
particularly grateful to Takahiko Ide, Animal Coordinator, Osaka
Municipal Tennoji Zoological Gardens, Japan, for providing us
with unpublished observations and photographs of their polar
bears, GoGo and Icchan. We also thank David McGeachy,
Wildlife Research Division, Environment and Climate Change
Canada, for technical assistance with the gures; Gavin Young,
GYPhoto, Calgary, for creating the screenshot for Figure 2d from
a low density video made by Tennoji Zoological Garden; Dr.
Lea Stirling, University of Manitoba, for translation of the Latin
quote from Fabricius (1780); Ms. Bonni Gallinger, University
of Alberta Library, for her perseverance with hunting down old
and obscure references; Dr. Ian Gjertz and Dr. A. Kochev for
searching published and unpublished records in Norwegian and
Russian from Svalbard and Chukotka respectively, as well as
their own eld notes, for possible records of tool use by polar
bears; Dr. Pamela Wong for permission to cite her TEK record
of tool use made during an interview with a hunter from Arctic
Bay; and Rod Vallee and Dr. M.K. Taylor for permission to use
unpublished photos.
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