sign in sign up
<<
Home , Brown bear, Grizzly bear, Wolf, Wolf reintroduction

SHORTCOMMUNICATIONS

Interactions between and female grizzly with cubs in Yellowstone

A. 3 Kerry Gunther1 and Douglas W. Smith2'4 adult males, solitary adult females, and female grizzly bears accompaniedby yearling or 2--old offspring ManagementOffice, PO Box 168, Yellowstone would occasionally usurp -killed and National WY Park, 82190, USA scavenge the remains. We hypothesized that these 2Wolf PO Box YellowstoneNational Project, 168, Park, cohorts of grizzly bears would be more successful than WY,82190, USA subadultsat usurpingwolf-kills. We furtherhypothesized Key words: lupus, cub bear, mortality, grizzly that due to potential danger to cubs, females with cubs interferencecompetition, interspecific killing, klepto- would not attemptto displacewolf packs from theirkills. Yellowstone National , arctos, wolf, Our of interactions between Park monitoring interspecific wolves and bears is From wolf Ursus15(2):232-238 (2004) grizzly ongoing. reintroductionin 1995 until Januaryof 2003, 96 wolf- interactionshave been recorded(Ballard et al. 2003; D. Smith, National Park Service, Yellowstone NationalPark, , USA, unpublisheddata). Here we observationsof interactionsbetween wolves Gray wolves (Canis lupus) were extirpated from report and female bears with cubs and evidence of wolf Yellowstone NationalPark (YNP) by the 1920s through grizzly bear cubs near carcasses. Due to predatorcontrol actions (Murie 1940,Young and Gold- packs killing grizzly man 1944, Weaver 1978), then reintroducedinto the grizzly bears' low reproductiverate (Schwartz et al. and statusas a threatened park from 1995 to 1996 to restore ecological integrity 2003) (USFWS 1993), the effects of wolves on carcass and cub and adhere to legal mandates (Bangs and Fritts 1996, availability survival is an Phillips and Smith 1996, Smith et al. 2000). Prior to importantconsideration for wolf reintro- reintroduction,the potential effects of wolves on the duction and grizzly bear conservationefforts. YNP ha in the states of region's threatenedgrizzly bear (Ursus arctos) popula- encompasses 891,000 tion were evaluated (Servheen and Knight 1993). In Wyoming, ,and ,USA. The parkcontains areas where wolves and grizzly bears are sympatric, a variety of habitatsfrom high elevation alpine to low interspecifickilling by both species occasionally occurs elevation sagebrush (Despain 1990). YNP (Ballard 1980, 1982; Hayes and Baer 1992). Most and the surroundingarea (GreaterYellowstone Ecosys- agonistic interactionsbetween wolves and grizzly bears tem, GYE) support an estimated 56,100 (Cervus involve defense of young or competition for carcasses elaphus), 29,500 (Odocoileus hemionus), (Murie 1944, 1981; Ballard 1982; Horbeck and Horejsi 5,800 (Alces alces), 3,900 bighorn ( 1986; Hayes and Mossop 1987; Kehoe 1995; McNulty canadensis), 3,600 (Bison bison), and smaller et al. 2001). Servheen and Knight (1993) predictedthat numbers of whitetail deer (Odocoileus virginianus), reintroduced wolves could reduce the frequency of mountaingoat (Oreamnosamericanus), and pronghom winter-killed and disease-killed ungulates available (Antilocapra americana) (U.S. Fish and for bears to scavenge, and that grizzly bears would Wildlife Service 1994). Large in the GYE occasionally usurp wolf-killed carcasses. include grizzly bears, American black bears Servheen and Knight (1993) hypothesized that in- (U. americanus), wolves, and mountain lions ( terspecific killing and competition for carcasses would concolor). In 2002, the reintroducedwolf populationin have little or no populationlevel effect on either species. the GYE was estimated at 273 wolves in 31 packs As a component of post-reintroductionwolf and (Smith et al. 2003a). More than 90% of the prey killed grizzly bear monitoringprograms, interspecific interac- by wolves in the GYE is elk (Smith et al. 2003b). Other tions between the species were recorded.We expected prey species killed by wolves include deer, bison, and reintroducedwolves to occasionally kill grizzly bears, moose, but individually none of these prey comprise especiallycubs-of-the-year (cubs). We also predictedthat >2% of GYE wolves' diet. The GYE grizzly bear populationis estimatedat 280-610 bears (Eberhardtand Knight 1996). The GYE is unique among areas [email protected] [email protected] inhabited by grizzly bears in because

232 SHORTCOMMUNICATIONS 233

Fig. 1. An interaction between gray wolves and a female grizzly bear with 2 cubs-of-the-year in Pelican Valley, Yellowstone National Park,Wyoming, USA, 2000. The wolves are on the bank of the creek, which is 2-3 meters higher than the bears in the creek bottom. This makes the wolves appear larger in proportion to the bears than they were (photo by D. Smith). of the substantial consumption of ungulate by observed interactingwith wolves. Only 7 (7%) inter- bears (Mattsonet al. 1991, Mattson 1997). Priorto wolf actions between wolves and females with yearlings or reintroduction,GYE grizzly bears obtained ungulate two-year olds were recorded. meat primarily by scavenging winter-killed elk and Of the 8 interactions between wolves and female bison carcassesin spring (Greenet al. 1997), by preying grizzly bears with cubs, 5 were at carcasses, 2 were at on elk calves in late spring and early summer (Gunther wolf rendezvoussites, and 1 occurredat a neutralsite. In and Renkin 1990), and by preying on and scavenging 3 of the 5 interactionsat carcasses(Observations 1, 5, 8; rut-weakened and rut-killed elk and bison in late Table 1), the bear family groups were displaced by summer and fall (Mattson 1997). wolves regardlessof the numberof wolves present(1-5 wolves). In 1 of these interactions(Observation 1; Table 1), a larger bear, probably a male, was feeding on the Interactionsbetween wolves and carcass before the female with cubs approached.After female grizzlies with cubs the lone bear left the carcass, a wolf fed on the carcass From 1995 through 2002, 96 wolf-grizzly interac- and the female with cubs left the area.The outcome of 1 tions were recorded (Ballard et al. 2003, D. Smith, interactionnear a carcass was neutral (Observation2; unpublished data). Only 8 (8%) of these interactions Table 1; Fig. 1). A female grizzly with 2 cubs were between wolves and female grizzly bearswith cubs encountered 4 adult wolves that were walking away (Fig. 1). Females with older offspring were also rarely from the carcass of a bull elk that was being controlled

Ursus 15(2):232-238 (2004) 234 SHORTCOMMUNICATIONS

Table 1. Interactions between wolves and female grizzly bears with cubs in Yellowstone National Park, 1995-2002. Dominant Observation Date Bears Wolves Location species 1 6 Aug 1998 Adultfemale, 1 cub 1 adult Carcass Wolf 2 12 Jul 2000 Adultfemale, 2 cubs 4 adult Carcass Neutrala 3 17 Jun 2001 Adultfemale, 2 cubs 4 adult,2 yearlings Carcass Bear 4 11 May2002 Adultfemale, 2 cubs 1 adult, 1 yearling n/a Bear 5 22 May2002 Adultfemale, 1 cub 1 adult,2 yearlings Carcass Wolf 6 31 Jul 2002 Adultfemale, 3 cubs 5 adult,3 pups Rendezvous Wolf 7 8 Aug 2002 Adultfemale, 3 cubs 3 pups Rendezvous Neutral 8 21 Sep 2002 Adultfemale, 1 cub 2 adult, 1 yearling, Carcass Wolf 2 unknown alone adultbear had possession of bullelk carcass, female with2 cubs walkingtoward the carcass interactedwith 4 wolves leaving the carcass. by a single grizzly bear. After a brief standoff, the harassed them. At 0734 hours, after feeding on the wolves continued walking away from the carcass and carcass for about 48 minutes, the bears left the kill and the female with cubs continued walking toward the walked away to the southwest. The wolves did not carcass. Although the interactionwith the wolves was harassthe bears as they left. None of the bears was hurt. neutral,the female with cubs did not attemptto usurpthe Two encountersbetween wolves and female grizzly carcass from the single adult bear. bears with cubs were observed at wolf rendezvoussites. In the other interactionat a carcass (Observation3, In late July 2002 (Observation 6, Table 1), 5 adult Table 1), a female with 2 cubs successfully usurped wolves and 3 wolf pups were at their rendezvous site a carcass from 6 wolves. On 17 June 2001 at 0606 when a female grizzly with 3 cubs walked throughthe hours,6 membersof the DruidPeak were observed site. One wolf approachedthe bears and followed them in LamarValley feeding on the carcassof a cow elk they out of the area and no furtherinteractions ensued. One had probably killed the previous night. The 6 pack week (Observation7, Table 1) later, the same 4 bears members present included radiomarkedwolves 21 (the walked through the same wolf rendezvous site when alpha male) and adults 106F, 217F, and 224M, as well only the 3 wolf pups were present. The pups fled the as two unmarkedyearlings. The remaining20 adult and area upon sighting the bears;the bears left the area with yearling wolves of the pack were not at the carcass, nor no visible response to the pups. were the 11 pups from two litters. At 0614 hours, an One other interactionbetween wolves and a female adult female grizzly bear with 2 cubs was observed grizzly bear with cubs did not involve a carcass or approachingthe carcass from the west. When the bears rendezvoussite (Observation4, Table 1). A female with neared the carcass, the wolves circled and confronted 2 cubs was walking within 1 km of a wolf den site when them. As the bears faced wolves that were directly in 2 wolves approachedher. The adult bear charged at the frontof them, other wolves rushedin and bit at the bears wolves. The wolves stoppedtheir approach and retreated from behind. The cubs stayed directlybeside or beneath but did not leave the area. The female and cubs left the theirmother as she slowly continuedtoward the carcass. area, and no other interactionwas recorded. Periodically, the female stopped to protect herself and lunged and swatted at the wolves. At times all 3 bears lunged togetherat an approachingwolf; other times the adult or cubs lunged independently at approaching Interspecific killing of grizzly wolves. cubs by wolves Several times the wolves completely stopped the Although the interactions were not observed, we bears' progress toward the carcass as the bears whirled documented 2 incidents in which wolf packs likely around to face the circling wolves. The bears took killed grizzly bear cubs. The first incident occurred in approximately20 minutes to move the final 100 meters late June or early July. On 2 July 2001, we received to the carcass. At 0646 hours the bears reachedthe kill a reportof a dead grizzly bear cub near Alum Creek in and began to scavenge. The wolves continued to circle . We hiked to the site 2 days later and the scavenging bears, but only occasionally rushed and retrievedthe carcass of a male grizzly bear cub that we

Ursus 15(2):232-238 (2004) SHORTCOMMUNICATIONS 235

Table 2. Center-to-center, width measurements (mm) Peak wolf pack were observed sniffing, chewing on, and of upper and lower canines from reference skulls of playing with the carcass of a grizzly bear cub near the black wolves, and grizzly bears, bears, gray moun- bull bison carcass.We investigatedthe site and retrieved tain lions in the Greater Yellowstone . the carcass of a female grizzly bear cub. The cub had Canine Mean SD Range multiple canine puncture wounds to its body but was width Species (mm) (mm) (mm) Number <5% consumed. Field inspection of the carcass in- Grizzlybear Upper 58 5 48-69 35 dicated that the wounds were consistent with attackby Lower 53 6 35-66 35 a large predator.Circumstantial evidence suggested that Black bear Upper 50 4 43-60 31 Lower 45 4 37-55 31 the cub had likely been killed by either the Druid Peak Graywolf Upper 45 3 40-53 33 pack or the single adult grizzly bear observed at the Lower 40 3 35-47 33 bison carcass the previous night. The Druid Peak pack Mountainlion Upper 40 4 29-49 62 Lower 35 4 23-41 62 consisted of 6 adults, 20 yearlings, and two litters totaling 11 pups, for a total of 37 pack members(Smith and McIntyre2002). The pups had not yet left the den sites and had not been observedat the bison carcass.The estimatedhad been dead for 3 to 5 days. The carcasshad nearestclimbable escape was 336 meters away. The been picked at by small avian but was less nearestcontiguous forest large enough to provideescape than 5% consumed. Field of the carcass inspection or hiding cover was 1,193 meters away. revealed that the dead cub had canine puncturewounds The cub carcasswas retrievedfor laboratorynecropsy to the body and head as well as a crushed skull, in- to determinethe species of predatorthat killed it. The dicatinginfliction by a large The nearestclimb- predator. cub weighed 22.7 kg, was in fair to good postmortem able escape tree was 111 meters The nearest away. condition, and prior to death had been in good forest to or contiguous large enough provide escape physiologic condition with no evidence of disease. Bite hiding cover was 397 meters Fresh bear away. grizzly marks were observed over the majority of the body. and wolf tracks were observed but were nearby, Center-to-center distance between matching canine probably left after the cub had been killed (based on puncture wounds associated with hemorrhage and recent A bull elk carcass that was >90% heavy rains). traumatizedtissue (indicatingoccurrence while the cub consumedwas found 50 meters southeast approximately was still alive) measured33-44 mm, most >39 mm. of the dead cub. The of the elk carcass was Although no one observed either incident, available inverted, the suggesting scavenging by bears;however, evidence from the carcasses suggests that wolves killed cause of death was unknown. both cubs. The distances between canine A puncture laboratory necropsy was performed on the cub wounds were 38-42 mm and 33-44 mm on the cubs carcassto determinethe of thatkilled it. species predator killed in Haydenand Lamar Valleys, respectively,consis- The cub was in average physiologic condition prior to tentwith the center-to-centerdistances between canines of death. Examination of the carcass revealed numerous wolves, mountainlions, and small black bears from the puncturewounds to the head, chest, and abdomen.The GYE (Table 2). Canine widths in those ranges are too and of the skull were parietal temporalportions crushed, small to have been inflictedby grizzly bears (Table 2). several ribs were broken, and the abdominal region by mountain lions is not likely in either showed trauma. The distance between the centers of incident. In YNP, mountain lions typically inhabit canine wounds was measured from matching puncture Douglas-fir (Pseudotsuga menziesii) and spruce (Picea the hide. Distances between wounds puncture ranged engelmannii)-fir (Abies lasiocarpa) forest types con- from 38 to 42 mm. taining numerousrocky canyons and outcrops(T. Ruth, The second incident occurredat the carcass of a bull Horocker Wildlife Institute,Gardiner, Montana, USA, bison that died in Lamar Valley on 3 August. Prior to personal communication,2001). Both kill sites were in death, the bison was observed with a wound on its side large, nearlytreeless sagebrushgrasslands, not typical of caused another bull the rut. likely by during Grizzly mountainlion habitatin the GYE (Murphyet al. 1999), bears were first observed feeding on the carcass on the and lions are rarely observed in the non-forested of 7 A female bear with 2 morning August. grizzly cubs portions of either Hayden or Lamar Valleys (T. Ruth, as well as a single adult grizzly bear were observed personnelcommunication, 2001). Both cubs were killed the bison carcass on scavenging the night of 10 August. near the carcasses of large ungulates that had attracted On 11 at 0543 10 members of the August hours, Druid grizzly bears and wolves. The presence of grizzly bears Ursus 15(2):232-238 (2004) 236 SHORTCOMMUNICATIONS and wolves would likely have precludedscavenging by Discussion mountain lions, which are smaller than bears and, as Female grizzly bears with cubs were successful at solitary , are vulnerableto wolf packs (Murphy usurpingcarcasses from wolves in only 1 of 5 observed et al. 1998). These physical and behavioral character- interactionsat carcasses. Wolves displaced the female istics would have made it difficult for mountainlions to grizzly bears with cubs in 3 interactions observed at defend themselves against grizzly bears and wolves at carcasses; in 1 incident the outcome was neutral for carcasses located so far from escape . a carcass in the possession of a large adult grizzly bear Predation by black bears is not likely either. Both that displacedboth wolves and a female bear with cubs. grizzly cubs were killed in large, non-forestedareas far Althoughwe documented1 case of a female grizzly bear from forest cover. In YNP, black bears are rarely with cubs usurping a carcass, interactions between observed far from forest cover in large non-forested wolves and grizzly bears with dependent young were areas (Guntheret al. 1995). Due to their smaller body rare during our study. Avoidance of wolves by female size, black bears are at a competitive disadvantagewith grizzlies with cubs is likely advantageous, as we 2 cubs that were killed wolves. grizzly bears in large non-forestedareas (Herrero1979). documented probably by Ourdocumentation of an adultfemale bearwith Black bears are generally subordinateto (Barnes and grizzly 2 cubs an elk carcass from 6 Bray 1967) and are sometimes killed by grizzly bears successfully usurping members of the Druid Peak is to our (Arold 1930, Mattsonet al. 1992, Guntheret al. 2002). pack contrary that due to to cubs, females It is unlikely that black bears would attempt to kill hypothesis potentialdanger with cubs would not attemptto displace wolf packs from grizzly bear cubs, which are usually accompaniedand kills. In this incident,the wolves had been feeding on the aggressively defended by their mothers. It is also elk carcass before the female grizzly bear with cubs unlikely that black bears would compete with wolf arrivedand may have alreadybeen gorged and satiated. packs and grizzly bears at ungulatecarcasses located so Wolves with full stomachsmay give up carcasses more far from escape trees or forest cover. readilythan hungry wolves. In addition,only 6 of the 26 Elk, the primary prey of wolves in the GYE, are pack members (not counting pups) were present, likely abundant in Hayden and Lamar Valleys, which are contributingto the bearfamily group's success in usurp- occupied by the Nez Perce and Druid Peak wolf packs, ing the carcass. Although the energy gained by female respectively (Smith et al. 2003b). In addition,the range grizzly bears with dependentcubs that usurpwolf-killed in distances between canine puncture wounds in the ungulates is potentially significant, there are also risks hides of both cubs that were attackedby suggests they associatedwith ,as demonstratedby the more than one , consistent with by predation 2 cubs killed by wolf packs nearungulate carcasses. and hunt in wolves that typically live, travel, packs Our documentationof 2 incidents of probablekilling Paradiso and Nowak but not (Mech 1970, 1982), by of grizzly bear cubs by wolf packs is consistentwith our mountain lions or black bears solitary (Dixon 1982) predictionthat interspecifickilling would occur follow- (Jonkel 1978, Pelton 1982). ing reintroductionof wolves to the GYE. Both incidents of We used the center-to-centerdistance matching occurrednear carcasses of large ungulatesthat attracted canine puncturewounds in the hides of the dead cubs the bears and wolves. In both incidents it appearedthat to aid in determiningthe species of predatorthat killed the cubs were attacked and bitten by more than one them. Use of canine puncture wound width measure- wolf, which is consistent with wolf-wolf intraspecific ments is an imperfectscience. Multiple bites to flexible killing. The wolves did not consume the cubs in either skin capable of stretching or shrinking make such incident. In the 8 (1995-2002) since implementa- measurementsimprecise. In additionto canine puncture tion of the GYE wolf reintroductionprogram, these are wound width measurements,we used vegetation cover the first incidents documented in the GYE of in- , landscape physiographic features, and social terspecific killing of grizzly bear cubs by wolves. The behavior of local predators to aid in identifying the 2 grizzly bear cubs killed by wolves in 2001 represent countedthat species that likely killed the cubs. Although we cannot 3% of the 78 grizzly cubs (Haroldson2002) completely rule out predation by a mountain lion or year and <1% of the 556 cubs (Haroldson 2002) small black bear in either incident, the preponderance countedin the GYE for the 8-yearperiod following wolf bear cubs in of evidence suggests that wolves killed both grizzly reintroduction.However, because grizzly cubs. the GYE are not radiomarked(M.A. Haroldson et al.

Ursus 15(2):232-238 (2004) SHORTCOMMUNICATIONS 237

InteragencyGrizzly Bear Study Team, NorthernRocky BANGS, E.E., AND S.H. FRITTS.1996. Reintroducingthe gray Mountain Science Center, Montana State University, wolf to central Idaho and Yellowstone National Park. Bozeman, Montana,USA, unpublisheddata), not all cub Wildlife Society Bulletin 24:402-413. mortalityis detected. BARNES,V.G., AND O.E. BRAY. 1967. Population character- istics and activities of black bears in Yellowstone National These observations lend insight into interference Park. Final Wildlife Research competition between wolves and grizzly bears and Report, Unit, Colorado State Fort Collins, Colorado, USA. factors that contributeto of grizzly University, interspecifickilling D.G. 1990. Yellowstone of bearcubs wolves. Further of DESPAIN, vegetation:consequences by monitoring wolf-grizzly environment and in a natural Roberts bear interactions our of the history setting. may expand knowledge Rinehart,Boulder, Colorado,USA. relative adultfemale bears that energy gained by grizzly DIXON, K.R. 1982. Mountain lion. Pages 711-727 in J.A. wolf-killed in relation to the costs in usurp ungulates, Chapmanand G.A. Feldhamer,editors. Wild of terms of increased cub associated with mortality NorthAmerica: Biology, management,and economics. John kleptoparasitism. HopkinsUniversity Press, ,, USA. EBERHARDT,L.L., ANDR.R. KNIGHT. 1996. How many grizzlies in Yellowstone? Journal of Wildlife Management 60: 416-421. Acknowledgments GREEN, G.I., D.J. MATTSON, AND J.M. PEEK. 1997. Spring We thank R. McIntyre, D. Stahler, K. Murphy, D. feeding on ungulatecarcasses by grizzly bears in Yellow- Guernsey,and R. Stradleyfor assistancecollecting data stone National Park. Journal of Wildlife Management on wolf-grizzly bearinteractions. D. ,T. Wyman, 61:1040-1055. and S. Chin helped retrieve wolf-killed cub carcasses GUNTHER, K.A., AND R.A. RENKIN. 1990. Grizzly bear on elk calves and other fauna of Yellowstone and helped investigate the kill sites. N. Anderson predation National Park. InternationalConference on Bear Research conducted laboratorynecropsy of the cubs. N. Varley and 8:329-334. and R. McIntyreprovided accounts of the incident they Management , M.J. BIEL, K.A. CHURCHILL, AND R.L. DANFORTH. witnessed in which a female grizzly bear with cubs 1995. Changing problems in Yellowstone bear manage- usurped a wolf-killed elk carcass. T. Ruth provided ment, 23 years after the 85-110 in A.P. canine width measurementsfrom GYE mountainlions. dumps. Pages Curlee, A.M. Gillesberg, and D. Casey, editors. Greater D. Irelandand T. Schock assisted with measurementsof Yellowstone predators, ecology and conservation in canine widths from referenceskulls. We thankD. Boyd a changing landscape. Proceedings of the Third Biennial and an reviewer as well as EditorR. Harris anonymous Conference on the Greater Yellowstone Ecosystem. and Technical EditorM. Munson-McGeefor comments Northern Rockies Conservation Cooperative, Jackson, that improvedthis manuscript.R. Grayprovided helpful Wyoming, and Yellowstone National Park, Mammoth, editorial comments. The Yellowstone Center for Re- Wyoming, USA. sources provided support for wolf and grizzly bear , N. ANDERSON,AND L. WAITS.2002. Probable researchand monitoringprograms in YNP. grizzly bear predation on an in Yellowstone National Park. Ursus 13:372-374. HAROLDSON,M.A. 2002. Unduplicatedfemales. Pages 12-16 in C.C. Schwartz and M.A. Haroldson, editors. Yellow- Literaturecited stone grizzly bear investigations: Annual report of the ARNOLD,B. 1930. Cannibal bear. Yellowstone Nature Notes InteragencyGrizzly Bear Study Team, 2001. U.S. Geologic 7(8):54. Survey, Bozeman, Montana,USA. ANDD.H. BALLARD,W.B. 1980. bear kills gray wolf. Canadian HAYES,R.D., MOSSOP.1987. Interactionsof wolves, Field-Naturalist94:91. Canis lupus, and brown bears, Ursus arctos, at a wolf den . 1982. Gray wolf- relationships in the in the NorthernYukon ().Canadian Field-Naturalist Nelchina Basin of south-centralAlaska. Pages 71-80 in 101:603-604. F.H. Harringtonand P.C. Paquet, editors. Wolves of the , AND A. BAER. 1992. Brown bear, Ursus arctos, world. Noyes Publications,Park Ridge, , USA. preying upon gray wolf, Canis lupus, pack. Canadian , L.N. CARBYN, AND D.W. SMITH. 2003. Wolf Field-Naturalist107:373-374. interactionswith non-prey. Pages 259-271 in L.S. Mech HERRERO,S. 1979. Black bears: the grizzly's replacement? and L. Boitani, editors. Wolves: ecology, behavior, and Pages 179-195 in D. Burke, editor. The black bear in conservation.The University of Chicago Press, Chicago, moder North America. Boone & Crockett Club. The Illinois, USA. Amwell Press, Clinton, New Jersey, USA.

Ursus 15(2):232-238 (2004) 238 SHORTCOMMUNICATIONS

HORNBECK,G.E., ANDB.L. HOREJSI.1986. Grizzly bear, Ursus economics. John Hopkins University Press, Baltimore, arctos, usurps wolf, Canis lupus, kill. Canadian Field- Maryland,USA. Naturalist100(2):259-260. PELTON,M.R. 1982. Black bear. Pages 504-514 in J.A. JONKEL,C. 1978. Black, brown (grizzly), and polar bears. Chapmanand G.A. Feldhamer,editors. Wild mammalsof Pages 227-248 in J.L. Schmidt and D.L. Gilbert, editors. North America: Biology, management, and economics. Big of North America, ecology, and management. John HopkinsUniversity Press, Baltimore,Maryland, USA. Stackpole Books, Harrisburg,Pennsylvania, USA. PHILLIPS, M.P., AND D.W. SMITH. 1996. The wolves of KEHOE,N.M. 1995. Grizzly bear, Ursus arctos, wolf, Canis Yellowstone. VoyageurPress, Stillwater,, USA. lupus, interactionin Glacier National Park, Montana.The SCHWARTZ,C.C., S.D. MILLER, AND M.A. HAROLDSON. 2003. CanadianField-Naturalist 109(1):117-118. Grizzly bear. Pages 556-586 in G.A. Feldhammer,B.C. MATTSON,D.J. 1997. Use of ungulatesby Yellowstone grizzly Thompson, and J.A. Chapman,editors. Wild Mammalsof bears Ursus arctos. Biological Conservation81:161-177. North America: Biology, management,and conservation. , B.M. BLANCHARD, AND R.R. KNIGHT.1991. Food Second edition. The John Hopkins University Press, habits of Yellowstone grizzly bears, 1977-1987. Canadian Baltimore,Maryland, USA. Journalof Zoology 69:1619-1629. SERVHEEN, C., AND R.R. KNIGHT. 1993. Possible effects of , R.R. KNIGHT, AND B.M. BLANCHARD.1992. Cannibal- a restored gray wolf population on grizzly bears in the ism and predationon black bears by grizzly bears in the Greater Yellowstone Area. Pages 28-37 in R.S. Cook, Yellowstone Ecosystem, 1975-1990. Journalof - editor. Ecological issues on reintroducing wolves into ogy 73:422-425. Yellowstone National Park. Scientific Monograph NPS/ MCNULTY,D.R., N. VARLEY, AND D.W. SMITH.2001. Grizzly NRYELL/NRSM-93/22.U.S. Departmentof the Interior, bear, Ursus arctos, usurpsbison calf, Bison bison, captured National Park Service, Natural Resources Publication by wolves, Canis lupus, in Yellowstone National Park, Office, Denver, Colorado,USA. Wyoming. CanadianField-Naturalist 115(3):495-498. SMITH,D.W., ANDR. MCINTYRE.2002. Wolf pack size: How MECH,L.D. 1970. The wolf: the ecology and behavior of an did the Druid Peak pack get to be so big? International . The American Museum of Natural Wolf 12(1):4-7. History. The Natural History Press, Garden City, New , L.D. MECH, M. MEAGHER,W.E. CLARK,R. JAFFE, York, USA. M.K. PHILLIPS,AND J.A. MACK. 2000. Wolf-bison inter- MURIE, A. 1940. Ecology of the in the Yellowstone. actions in Yellowstone National Park. Journal of Mam- Fauna of the National Parks, Fauna Series 4. U.S. malogy, 81:1128-1135. GovernmentPrinting Office, ,D.C., USA. , D.R. STAHLER, AND D.S. GUERNSEY.2003a. Yellow- . 1944. The wolves of Mount McKinley. U.S. stone Wolf Project:Annual Report, 2002. YCR-NR-2003. Departmentof the Interior,National Park Service, Fauna NationalPark Service, Yellowstone NationalPark, Wyom- of the NationalParks of the , FaunalSeries 5. ing, USA. U.S. GovernmentPrinting Office, Washington,D.C., USA. , R.O. PETERSON,AND D.B. HOUSTON.2003b. Yellow- . 1981. The grizzlies of Mount McKinley. U.S. stone after wolves. BioScience 53:330-340. Departmentof the Interior,National Park Service, Scien- U.S. FISHAND WILDLIFE SERVICE. 1993. Grizzly bear recovery tific MonographSeries No. 14. U.S. GovernmentPrinting plan. Missoula, Montana,USA. Office, Washington,D.C., USA. . 1994. The reintroductionof gray wolves to Yellow- MURPHY, K.M., G.S. FELZIEN, M.G. HORNOCKER, AND T.K. stone NationalPark and centralIdaho. Final Environmental RUTH.1998. Encounter competition between bears and Impact Statement.Helena, Montana,USA. : Some ecological implications.Ursus 10:55-60. WEAVER, J. 1978. The wolves of Yellowstone. Natural , P. IANRoss, ANDM.G. HORNOCKER.1999. The ecology ResourcesReport 14. U.S. Departmentof Interior,National of anthropogenicinfluences on cougars. Pages 77-101 in Park Service, WashingtonD.C., USA. A. Peyton Curlee, S.C. Minta, and P.M. Kareiva, editors. YOUNG,S.P., ANDE.A. GOLDMAN.1944. The wolves of North Carnivores in : The Yellowstone experience. America.Dover Publications,, New York, USA. Yale UniversityPress, New Haven, Connecticut,USA. PARADISO,J.L., ANDR.M. NOWAK.1982. Wolves. Pages 460- Received: 9 January 2004 474 in J.A. Chapmanand G.A. Feldhamer,editors. Wild Accepted: 1 March 2004 mammals of North America: Biology, management,and Associate Editor: R.B. Harris

Ursus 15(2):232-238 (2004)