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Wendy Calvert and Ian Stirling Source: Bears: Their Biology and Management, Vol Interactions between Polar Bears and Overwintering Walruses in the Central Canadian High Arctic Author(s): Wendy Calvert and Ian Stirling Source: Bears: Their Biology and Management, Vol. 8, A Selection of Papers from the Eighth International Conference on Bear Research and Management, Victoria, British Columbia, Canada, February 1989 (1990), pp. 351-356 Published by: International Association of Bear Research and Management Stable URL: http://www.jstor.org/stable/3872939 Accessed: 03/01/2009 20:40 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http://www.jstor.org/action/showPublisher?publisherCode=iba. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit organization founded in 1995 to build trusted digital archives for scholarship. We work with the scholarly community to preserve their work and the materials they rely upon, and to build a common research platform that promotes the discovery and use of these resources. For more information about JSTOR, please contact [email protected]. International Association of Bear Research and Management is collaborating with JSTOR to digitize, preserve and extend access to Bears: Their Biology and Management. http://www.jstor.org INTERACTIONSBETWEEN POLAR BEARS AND OVERWINTERINGWALRUSES IN THE CENTRALCANADIAN HIGH ARCTIC WENDY CALVERT, Canadian Wildlife Service, 5320 122 Street, Edmonton, AB T6H 3S5 IAN STIRLING, Canadian Wildlife Service, 5320 122 Street, Edmonton, AB T6H 3S5 and Department of Zoology, University of Alberta, Edmonton, AB T6G 2E9 Abstract:There are few recordsof predationby polarbears (Ursus maritimus) on walruses(Odobenus rosmarus), although their distributions overlap extensively. During the late winter and early springfrom 1981 through 1989, we recordedinteractions between polar bears and walrusesin the centralCanadian High Arctic, where walrus movementsare severely restrictedin the winterby limited areasof open waterfor breathingand haulout holes. Predatorybehaviour of bearsand anti-predatorbehaviour of walruseswere observed. We found evidence thatpolar bears made woundingbut non-fatalattacks on 3 walruses,killed 3 walruses,and probably killed 4 others. One walrus was frozen out of its breathing hole and vulnerable to predation. Although the vulnerability of walruses to polar bear predation would vary with habitats and seasons, it is clear that polar bears are importantpredators of walruses in the centralCanadian High Arctic in late winter-earlyspring. Int. Conf. Bear Res. and Manage: 8:351-356 Walrusand polar bear distributionsoverlap in a vari- ety of habitats and seasons including the floe edge or drifting pack ice throughout the year in some areas, terrestrialhaulouts where all the ice has melted in the summer,and polynyas of variablesizes duringthe winter. The vulnerabilityof walrusesto predationby polarbears may vary significantly among these sharedhabitats, but thereare few confirmedreports of predation(Perry 1966, Kiliaanand Stirling 1978) andlittle quantitativeinforma- tion about the nature and magnitude of the predation. Most of the observationsof interactionsbetween polar bears and walruses have been made at terrestrialor ice- edge hauloutsor in pack ice. Polar bears are powerful predators,capable of taking large prey such as bearded seals (Erignathusbarbatus) (Stirlingand Archibald 1977) and belugas (Delphinapterus leucas) (Lowry et al. 1987), but walruses are the largest of the polarbear's possible prey, and they are able to use their tusks for defence. Loughrey (1959) felt there was little doubtpolar bearsprey on calves and subadults,but found factual accounts scarce. Fay (1982) statedthat he knew of no confirmed records of predationby bears on walruses. He concludedthat contact between polarbears and walruses occurredmainly in summerand that only younger walruses are really vulnerable to predation. AlthoughFay (1985) listed predationby polarbears as 1 of 3 primarycauses of mortality among walrus calves (along withpredation by killer whales [Orcinusorca] and crushing),he noted that Mansfield (1958) has calculated Fig. 1. Kills or attacks by polar bears on walruses in the Penny Strait and Queens that total of walrus calves is low to Channel area from 1981 through 1988: 1)10 Apr 1981, confirmed kill of young mortality compared adult, found partially eaten, tusks <30 cm; 2) 3 Apr 1982, confirmed kill, 1 large otherpinnipeds.It is hardto assess if this predationwould bear pulling adult walrus (length 247 cm) from hole, 2 walruses hauled out be to the nearby; 3) 26 Apr 1983, evidence of attack but not kill; 4)12 Apr 1984, young adult significant population. female frozen out >2 days, not killed, tusks -20 cm; 5) 19 Mar 1985, possible In the centralCanadian High Arctic, small groups of attack, blood around hole; 6) and 7) 30 Mar 1985, old kill of 1 adult and 1 yearling walruseswinter in a of 50- 100 walrus, carcasses dismembered, adult female polar bear and 2-year cub feeding polynyas, including group on them; 8) 30 Mar 1985, confirmed fresh kill of young female walrus, tusks 10 walruses at the Dundas Polynya at Cape Collins (Fig. 1) cm, 2 adult bears feeding; 9) 11 Apr 1985, possible attack, blood near hole, bear on the northeastern of Dundas Island et al. tracks windblown; 10) 21 Apr 1986, kill of young walrus, length 185 cm, tusks tip (Stirling 3.8 cm; 11) 23 Apr 1987, adult male carcass (length >275 cm, tusks 33 cm) at tide 1981). Open waterwhere walrusescan breatheand feed crack, probably killed by a polar bear, scavenged by many bears. 352 BEARS-THEIR BIOLOGY AND MANAGEMENT duringthe winteris maintainedthere and at severalother overlookingthe polynya. On an opportunisticbasis, we locations in easternPenny Straitby strongtidal currents recordedthe huntingbehaviour of polarbears, occasional (Tophamet al. 1983). In addition,multiyear floes that interactionsbetween polar bears and walruses, and the become groundedin shallow water in the late summer behaviourof walruseswhile hauledout andvulnerable to throughoutthis regionwill remainfrozen in placethrough predation. the winter. These floes are rockedby tidal currentsand We used a helicopter to survey Penny Strait and winds, creating a border of weaker broken ice where Queens Channelalso. On each survey, we followed the walruses are also able to breathe and haul out. The same generalroute north from the DundasPolynya along walrusesmay remainat these floes for weeks or months the western coast of Devon Island and returnedvia the at a time (Stirlinget al. 1981: Fig. 3). middle of Penny Straitand Queens Channelpast Hyde On 2 occasions,Kiliaan and Stirling (1978) foundlone ParkerIsland, the CheyneIslands, and the northernend of walruses,one an adult,the otheralmost 2-years-old,that Baillie-HamiltonIsland (Fig. 1). The exact routevaried had been attackedand killed by a polarbear at a haulout withinand among years, depending on the distributionof hole. They also reporteda kill by Inuit of a walrus at a walruses,changes in ice conditions,and prevailing weather frozen-overhole, and an observationof an adult walrus conditions. Surveyswere conducted2-6 times each year thathad been attackedby a polarbear but survived. From at approximately2-week intervalsbetween mid-March these observations,they suggested that walruses over- andearly May andcovered a distanceof 150-400 km. We winteringin areas with restrictedbreathing and haulout flew betweenabout 1000 and2000 hrsEST, at an altitude sites might be more vulnerable to predation,and that of about70 m and an airspeedof about 100 km/hr. The predationby polar bears might be more frequent than surveyswere primarilyto map walrusand polynya distri- previouslyseemed apparent.This paperpresents obser- bution and recordthe underwatervocalizations of wal- vations of predationby polar bears on both young and ruses and seals for anotherstudy, but we also noted all adultwalruses in a polynyaarea during the late winterand polar bears,polar bear tracks(and an estimationof their early spring. freshness), and any indicationsof interactionsbetween We gratefully acknowledge the supportof the Polar polar bears and walruses. When a walrus carcass was ContinentalShelf Project,the CanadianWildlife Service, found, ice conditionsand presenceof bears were noted. World Wildlife Fund (Canada),and the Departmentof When possible, measurementsand photographswere Fisheriesand Oceans. We thankJ.J. Burs, Fairbanks;T. taken, and a tooth was collected for age determination. Eley andK. Frost,Alaska Department of Fish andGame, Fairbanks;D. Grant,Yellowknife; and M.Taylor, North- RESULTS AND DISCUSSION west TerritoriesDepartment of Renewable Resources, to use their observations. In for permission unpublished Sightings of Polar Bears the field, we had the help and good company of D. Polarbears den, huntand feed on seals, andmate in the H. I. D. N. B. Andriashek, Cleator, Cote, Keith, Lunn, study area(Stirling et al. 1984), andbears of all age- and J.J. A. Sjare, and C. Spencer. S.C.
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