Denning Characteristics of Brown Bears on Kodiak Island, Alaska Author(S): Lawrence J

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Denning Characteristics of Brown Bears on Kodiak Island, Alaska Author(s): Lawrence J. Van Daele, Victor G. Barnes, Jr., Roger B. Smith 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. 257-267 Published by: International Association of Bear Research and Management Stable URL: http://www.jstor.org/stable/3872927 Accessed: 03/01/2009 19:57

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http://www.jstor.org DENNINGCHARACTERISTICS OF BROWNBEARS ON KODIAKISLAND, ALASKA

LAWRENCEJ. VAN DAELE, Alaska Department of Fish and Game, 333 Raspberry Road, Anchorage, AK 99518 VICTOR G. BARNES, JR., U.S. Fish and Wildlife Service, 1390 Buskin River Road, Kodiak, AK 99615 ROGERB. SMITH,Alaska Department of Fishand Game, 211 MissionRoad, Kodiak, AK 99615

Abstract: Investigations of brown bear (Ursus arctos middendorffi) denning ecology in 2 areas of Kodiak Island, Alaska, revealed that subpopulations of bears living within 70 km of each other had developed noticeably different denning behaviors. One hundred and fifteen radio-collared brown bears were located in 321 dens. The relative order in which bears in various reproductive categories entered their dens was similar in both study areas; females entered dens earlier than most males, and pregnant females generally entered dens earliest. Female bears in Southwest Kodiak generally entered their dens 2 to 3 weeks later than their counterparts in the Terror Lake area. We hypothesize that this variation was related to the relative food availability in the 2 areas during late autumn. Emergence chronology was similar in both areas. Males were generally the 1st group to emerge from their dens, and females with new cubs were usually last. Bears at Terror Lake preferred steep slopes in alpine habitat for den sites. In Southwest Kodiak, midslope habitat and moderate slopes were preferred denning habitat. Two areas with high concentrations of dens were identified in the Terror Lake area. A high degree of fidelity to specific den sites was exhibited by individual brown bears on Kodiak. Two notable anomalies in denning behavior were observed in this study; use of multiple dens by 27 bears and failure to enter dens by 8 bears. Management implications of the differences in the denning ecology of these subpopulationsare discussed.

Int. Conf. Bear Res. and Manage. 8:257-267

The brown bear population on Kodiak Island is a (USFWS). We sincerely appreciateassistance received valuable resource that is intensively managed. Recent from numerousemployees of the ADF&G and USFWS investigationshave verified that the island supportsone throughoutall phasesof theseprojects. J.A. Patterson,M. of the densest populationsof brownbears recorded, with Vivion, T. Chatto, V. Lofstedt and C. Lofstedt, and an estimatedmean density of 1 bear/4.1km2 (Barnes et al. several otherpilots, providedexpert flying skills. Susan 1988). Approximately130 bearsare harvestedannually Malutinwas a valued assistantthroughout the projects, by sporthunters (Alaska Departmentof Fish and Game with her clerical skills and constantmoral support. [ADF&G] files) and the island has a reputation for producinglarge trophies(Nesbitt and Wright 1981). In STUDY AREA recentyears there has also been an increasein the number The Kodiak archipelago is located in the Gulf of of people visiting the island to view and photograph Alaska, approximately400 km southwest of the city of bears. Anchorage,Alaska (Fig. 1). KodiakIsland is the largest Past studies of bears on Kodiak have focused on island in the archipelago,encompassing 9,600 km2. The habits feeding (Clark 1957, Clark 1959, Atwell et al. region has a maritimeclimate characterizedby cloudy et al. 1980), reproduction(Hensel 1969), movements skies, cool temperatures,moderate to heavy precipita- and Hensel (Bers 1972, Bers et al. 1980) and harvest tion, and frequentwindstorms. Maximumtemperatures and Hensel (Troyer 1961, Troyer 1969). Althoughonly generally range from 13-18 C and winter temperatures limitedattention has been given to denning(Lentfer et al. below -6 C are infrequent. Annual precipitation at informationon 1972), denning ecology has utility for Kodiakcity averages157 cm, andoccurs primarily as rain disturbance avoiding to bearsin theirdens andin regulat- near sea level and snow in the higher elevations from harvest et al. ing (Schoen 1987). Octoberto May. In general,the southwestportion of the We investigated brown bear ecology in 2 separate island has warmer summers, cooler winters and less areasof KodiakIsland from 1982 to 1988 (Barnes 1986, precipitationthan the northernpart. The archipelago Smith and Van Daele 1988, Smithand Van Daele 1990). supportsa humanpopulation of 14,000, most of whom Brown bear in the 2 areas subpopulations lived within live in the city of Kodiak and 6 outlying villages. 70 km of each other, but occuped dissimilar habitats. The TerrorLake study area includes 774 km2on the of the of these bears Comparison denning ecology pro- northernportion of Kodiak Island. Inland topography vided an contrastin how had to interesting they adapted varies from rolling hills and gentle valleys to steeply each habitat . exploit successfully ascendingridges and peaks to elevationsof 1,340 m along for the researchat TerrorLake was Funding provided tributariesinto Kizhuyakand TerrorBays. Vegetation the Alaska Power the Kodiak by Authority, Electric varies from marine aquatics in the bays to hillsides Association, and the ADF&G. Research in Southwest covered with dense shrub thickets interspersed with Kodiakwas funded the U.S. Fish andWildlife Service by meadows (Smith and Van Daele 1990.) Alpine vegeta- 258 BEARS THEIR BIOLOGY AND MANAGEMENT

bears was 28 km2and 133 km2,respectively (Smith and Van Daele 1988). In Southwest Kodiak, the average annual home range size for radio-collaredfemale and male bears was 92 km2and 219 km2,respectively (Bar- nes 1990). No bearswere known to have used both study areas.

METHODS Data on denning chronology, den locations and bear reproductivestatus were collected duringweekly radio- trackingflights from April through December and monthly Southwest Kc flights from Januarythrough March. Den entrancedates Study Area were estimatedto be the midpointbetween the last date a bear was known to be out of its den and 1st date it was known to be in its den. When the period between re- location flights exceeded 20 days, den entrance dates were not calculated. Emergencedates were estimatedto 20 k m be at the midpointbetween the date of the last flight that a bearwas closely associated with its den and the date of the 1st flight it was no longer associated with its den. Close association was considered to be daily use of the den itself. Mean denning periods were calculated by Fig. 1. Location of Terror Lake and Southwest Kodiak brown bear study areas, the maximumand minimum number of in Kodiak Island, Alaska. averaging days the den. Maximum denning periods were the interval betweenthe last datea bearwas seen out of its den andthe tion includes low willow (Salix spp.), sedges (Carex 1st dateit was seen away fromits den. Minimumdenning spp.),and ericaceous heath. Salmonare abundant through- periods were the intervalbetween the 1st date a bearwas out the summer with pink (Oncorhynchusgorbuscha), known to be in its den and the last date it was known to chum (0. keta), andcoho salmon (0. kisutch)being most be in its den. Mean denningperiods were not calculated common. for bears that had a range of more than 40 days between The SouthwestKodiak study areaencompasses 1,231 the minimumand maximumdenning periods. km2between Uyak, Deadmanand Olga Bays. The topog- Estimatedslope categories (flat, gentle: <30%, mod- raphy is typified by wide flat valleys, rolling foothills, erate:30-45%, steep:>45%), aspects (8 categoriesbased and occasional areas of steep terrain. The highest peak on truebearing), vegetative cover andden locations were (997 m) andthe most ruggedterrain occur in the southeast recordedin the field. Elevation and distance data were portionof the study area. Lowlands supporta mosaic of derived from U.S. Geological Survey 1:63,360 topo- willow and herbaceouscover, with driersites dominated graphic maps. Den sites were categorized into 1 of 3 by heath vegetation (Barnes 1990.) Vegetation on mid- habitatcategories (alpine, midslope, lowland) based on elevation slopes is similarto thatin the TerrorLake area, elevation andvegetation characteristics within 1 ha of the but shrubthickets are not as extensive. Alpine vegetation site. Den constructiondata were collected duringground is similarto thatfound in the TerrorLake area,but is less visits to selected dens during the summer. Statistical extensive. Salmon are abundant from June through comparisonsof denning chronologies and den site char- October,and occur in greaternumbers and over a larger acteristicsbetween the 2 study areas and among repro- percentageof this studyarea than in the TerrorLake area. ductive categories (male, lone female, female with cubs- Sockeye (0. nerka), chinook (0. tshawytscha), coho, of-the-year [COY], and females with cubs >1 yr) were pink, and chum salmon all occur in this area. accomplished with analysis of variance tests, t-tests, Brownbear densities were similar in bothareas (1 bear/ Bonferroni z-tests and chi-squared contingency tests. 2.9 km2at TerrorLake and 1 bear/3.5 km2in Southwest Denningchronology was also analyzedby comparingthe Kodiak) (Barneset al. 1988), but home range sizes were percentage of radio-collared bears within the various considerablydifferent. At TerrorLake, the average an- reproductivecategories that were known to be in dens by nual home range size for radio-collaredfemale and male certain dates. The reproductivestatus was determined DENNINGCHARACTERISTICS OFBROWN BEARS * Van Daele et al. 259

Table 1. Mean den entrance dates for radio-collared brown bears, by reproductive category, in 2 study areas on Kodiak Island, Alaska, 1982-1988.

Study Reproductive Mean den Sample Standard area category entrancedate Rangea size deviation

TerrorLake Male 16 November 4 Nov.-14 Dec. 4 18.9 Lone femaleb 10 November 21 Oct.-2 Jan. 40 14.9 Female w/young 9 November 23 Oct.-14 Dec. 36 13.1 Pregnantfemale 5 November 15 Oct.-28 Nov. 27 11.2 Southwest Kodiak Male 12 December 3 Dec.-21 Dec. 2 12.7 Lone femaleb 26 November 22 Oct.-20 Dec. 12 18.9 Female w/young 3 December 17 Oct.-19 Jan. 47 21.9 Pregnantfemale 19 November 19 Oct.-29 Dec. 10 27.2 a Range of estimatedentrance dates. b May include some pregnantfemales that lost their newborncubs priorto the 1st post-denningobservation in the spring.

each spring at emergence. Some pregnantfemales may Den emergencein bothstudy areas generally began in have lost theirnewborn cubs priorto our 1st post-denning early April, althougha few individualsleft their dens as observations,and could have been misclassifiedas "lone early as February. A typical patternof emergence con- females". sisted of: 1) opening the den entrance;2) remainingnear or in the den for several days, interspersedwith short RESULTS forays in the immediateden vicinity; and, 3) abandon- One hundredand fifteen radio-collaredbrown bears ment of the den site (emergence). Chronologyof emer- (94 females and 21 males) were locatedin 321 dens (293 gence was generallythe reverseof entrancechronology, occupied by females and 28 by males). There were 184 with males emerging 1st, followed by lone females and dens (57%)used by 64 bearsat TerrorLake, and 137 dens females with yearlingand olderoffspring. Females with (43%) used by 51 bears in SouthwestKodiak. COY were usually the last group to emerge (Fig. 3). Mean emergence dates of females differed (P < 0.1) amongall reproductive categories at Terror Lake (Table 3). Denning Chronology In SouthwestKodiak, females with COY emerged later Typical denning behavior consisted of periods of than other females (P < 0.1), but emergence dates were excavationactivity interspersedwith extendedrest peri- similarfor lone females andfemales with olderoffspring ods. Bears often made several excavations in adjacent (P > 0.2). Bearsin SouthwestKodiak appeared to emerge locations priorto completing a den. somewhatearlier than their counterpartsat TerrorLake Bears at TerrorLake generally moved into denning areasby mid- to late October.In SouthwestKodiak, bears Table 2. Mean den entrance dates for radio-collared brown bears in 4 separate did not exhibit obvious movements into identifiable study areas in Alaska. denningareas, and they entereddens later(P < 0.1) than bears at TerrorLake These differences were (Table 1). Reproductivestatus (P < 0.1) for all female significant reproductivecatego- Study Lone Females Pregnant ries, averaging13.7 days differencefor pregnantfemales, area Males females with young females 17.4 for lone females, and24.6 for females with days days Southcentral sizes were insufficient young. Sample to test differences Alaskaa 16 Oct 14 Oct 15 Oct 13 Oct between the mean den entrance dates of males. Den Southeastern entrancedates in both areas were later than have been Alaskab 5 Nov (20)C 5 Nov (22)C 27 Oct (12)c 22 Oct (9)c reported in other brown bear populations in Alaska Terror (Schoen et al. 1987, Miller 1990)(Table2). Lake, Kodiak 16 Nov (31) 10 Nov (27) 9 Nov (25) 5 Nov In most cases, females entered dens earlier than did (23) males. Pregnantfemales generally entereddens earlier Southwest Kodiak 12 Dec (58) 26 Nov (43) 3 Dec (50) 19 Nov (37) than lone females or females with young (Fig. 2). Preg- nant females had an earlier a Miller(1990); females with 2-year-oldsincluded in the "lonefemale" mean entrancedate than did b category. Schoen et al. (1987). females with young in both study areas;however, these c Numbers in parenthesesindicate the difference, in days, from the mean den differences were not statisticallysignificant. entrancedates of bearsin similarreproductive categories in southcentralAlaska. 260 BEARS THEIR BIOLOGY AND MANAGEMENT

l DEN ENTRANCE BY REPRODUCTIVESTATUS i DEN EMERGENCEBY REPRODUCTIVESTATUS TERROR LAKE TERROR LAKESTUDY AREA 100

70 wz wz a 60 z z 50 Z z z w o L x w 40 l I CL

20 1 10 20 1 10 20 1 10 20 October November December January February

lone pregnant females lone females females males females females w/cubs males females w/new cubs w/older cubs

SOULTHWESTKODIAK STUDY AREA 100

70 z z a 60 z ? w 50 z z

10n

20 1 10 20 1 10 20 1 10 20 1 10 1015 251 5 15 25 1 5 15 25 1 5 15 25 1 5 15 25 1 5 15

October November December January February February March April May June July

Fig. 2. Chronology of den entrance by radio-collared brown bears in each Fig. 3. Chronology of den emergence by radio-collared brown bears in 2 study reproductive category in 2 study areas on Kodiak Island, Alaska, 1982-1988. areas on Kodiak Island, Alaska, 1982-1988.

(Fig. 3), but these differences were not statistically sig- stayed in their dens longer in the TerrorLake study area nificant. Den emergencedates in both areaswere similar thanin theSouthwest Kodiak study area (P < 0. 1)(Table5). to those reportedfrom other brown bear populationsin Females that emerged with COY did not have different Alaska (Schoen et al. 1987, Miller 1990)(Table4). mean denning periods between the 2 areas (P > 0.2). Maleshad the shortestmean denning period (135 days) Den entranceand emergence dates appearedto vary andfemales with COY had the longest (205 days). Bears annuallyin both studyareas, but datawere insufficientto in all reproductivecategories in both study areas had analyze these differences objectively. different mean denning periods (P < 0.05), with the exception of lone females compared to females that Den Site Characteristics emerged with yearling or older offspring. At Terror Fifty-six percent (n = 178) of the dens were in the Lake, lone females and females with yearling or older alpine habitatcategory, 43% (n = 139) in the midslope offspring were still differentbut at a slightly lower level category, and 2% (n = 3) in the lowland category. One of significance(0.1 > P > 0.05), andin the Southwestarea den was not located accuratelyenough to assign it to a females in these reproductivecategories did not have specific category. Radio-collaredbears at TerrorLake significantlydifferent denning periods (P > 0.2). Males occupied dens in alpine areas more frequentlythan did (P < 0.01), lone females (P < 0.05), and females that the bears in Southwest Kodiak (P < 0.1). The relative emerged with yearling or older offspring (P < 0.01) availability of each habitat type in each study area ex- DENNINGCHARACTERISTICS OF BROWN BEARS * Van Daele et al. 261

Table 3. Meanden emergence dates for radio-collaredbrown bears in 2 study areas on KodiakIsland, Alaska, 1982-1988.

Study Reproductive Mean den Sample Standard area categorya entrancedate Rangeb size deviation

TerrorLake Male 22 April 31 Mar.-24May 18 13.5 Lone female 2 May 23 Mar.-7Jun. 36 18.5 Female w/young 12 May 31 Mar.-7Jun. 31 15.9 Female w/coy 27 May 20 Mar.-13Jul. 15 27.1 Southwest Kodiak Male 8 March 1 Feb.-11 Apr. 2 48.8 Lone female 28 April 22 Mar.-22May 14 17.8 Female w/young 27 April 11 Mar.-8Jun. 61 20.3 Female w/coy 31 May 7 May-3 Jul. 18 15.6 a Based on 1st observationafter emergence; the "Lonefemale" category may include some pregnantfemales thatlost theirnewborn cubs priorto our 1st post-denning observation;"Female w/young" were those known to have emerged with yearlingor older cubs, females thatentered with cubs but emergedalone were excluded from this analysis;"Females w/coy" were those that were known to have emerged with cubs-of-the-year. b Range of estimatedemergence dates.

plained some of the variation(P < 0.01), but individual a critical factor in determiningsuitability of a den site. preferencealso appearedto play a role in den site selec- Den aspects differed between the 2 areas (P < 0.1). tion (Table 6). In both areas, dens were located in Northerlyaspects (north,northeast, and northwest) were lowlands less often than would be expected based on most frequently used for dens (33%) at Terror Lake, availability(P < 0.01). In theTerror Lake area, midslopes while in SouthwesternKodiak northerly aspects were the were used aboutequal to theiravailability (P > 0.1), and least frequentlyused (20%)(Table7). We collected no dens were located in alpine areasmore often thanwould data on the relative availability of various slopes and be expected(P < 0.1). Conversely,in SouthwestKodiak, aspects in the 2 areas. alpine areas were used about equal to their availability Gross den construction characteristicswere deter- (P > 0.1), and dens were located in midslope areasmore minedfor 135 dens, including:111 excavateddens (15 in oftenthan would be expected(P < 0.1). These differences TerrorLake and 96 in Southwest); 17 naturalrock cavi- were also reflected in the mean den elevations in the 2 ties (3 in TerrorLake and 14 in Southwest);5 snow dens areas. At TerrorLake, dens rangedfrom 91 to 1,189 m, (all in TerrorLake area); and, 2 snow dens in rockcavities with a meanof 665 m. In SouthwestKodiak, dens ranged (bothin TerrorLake area). Den dimensionsand structure from 128 m to 915 m, andwith a meanelevation of 457 m. were variable, and similar to those reported in other Mean den elevations varied annuallyand by sex, but no consistent trendswere evident. Fifty-two percent(n = 167) of the dens were located Table 4. Mean den emergence dates for radio-collared brown bears in 4 separate on steep slopes, 40% (n = 127) on moderateslopes, 8% study areas in Alaska. (n = 26) on gentle slopes, while no dens werefound on flat sites. Dens were found on steep slopes more often Reproductivestatusa (P < 0.1) at TerrorLake (65%)(n = 120) than in South- Study Lone Females Females west Kodiak (35%)(n = 47). Of those dens located on area Males females with youngb with coyC moderateor at gentle slopes TerrorLake, 80% (51/64) Southcentral were associated with cliffs or rock This asso- outcrops. Alaskad 23 Apr. 30 Apr. 4 May 15 May ciation with cliffs or rock outcrops on moderate and Southeastern gentle slopes suggests that these microhabitatswere Alaskae 19 Apr. 29 Apr. 16 May 11 May equivalentto steep slopes for meeting denning require- TerrorLake, ments. If this was the case, 93% (171/184) of the dens at Kodiak 22 Apr. 2 May 12 May 27 May TerrorLakewere in steepmicrohabitats. In contrast,only Southwest 11%of the dens in SouthwestKodiak that were on gentle Kodiak 8 Mar. 28 Apr. 27 Apr. 31 May or moderate were associated slopes with cliffs or rock a Determinedat 1st post-denningobservation. outcrops,resulting in a total of 32% (43/136) of the b Females with yearlingor older offspring. only c den sites in Females with cubs-of-the-year. steep microhabitats. d Miller( females with Aspects of den sites were variableand not 1990); 2-year-oldsincluded in the "lonefemale" category. apparently e Schoen et al. (1987). 262 BEARS-THEIR BIOLOGYAND MANAGEMENT

Table 5. Average denning periods of radio-collared brown bears in each Table 6. Relative distribution of den locations by habitat category for radio- reproductive category In 2 study areas on Kodiak Island, Alaska, 1982-1988. collared brown bears in 2 study areas on Kodiak Island, Alaska, 1982-1988.

Mean denning period in days(sample size in parentheses) Habitatcategory Study Lone Females Females Studyareaa Lowland Midslope Alpine Total area Males femalesa with youngb with coyC TerrorLake TerrorLake 157 (6) 176(31) 187 (20) 211 (15) % Area (km2) 26.6 (206) 33.1 (256) 40.3 (312) 774 km2 % Den sites (n) 1.7 (3) 26.8 (48) 71.5 (128) 179 dens SouthwestKodiak 91 (3) 160 (9) 149 (41) 198 (12) Southwest Kodiak Kodiaktotal 135 172 (40) 162 (61) 205 (27) (9) % Area (km2) 40.6 (500) 36.6 (451) 22.8 (281) 1,231 km2 a The"Lone female" category may include some pregnant females that lost their % Den sites (n) 0.0 (0) 73.9 (85) 26.1 (30) 115 den newborncubs prior to our1st post-denning observation. a Includesonly the area(km2) and the dens thatwere withinthe core studyareas; b Femalesknown to have with or oldercubs; females that emerged yearling bears which had home ranges within our study areas but denned outside of the enteredwith offspring but emerged alone were excluded from this analysis. areaswere excluded from this analysis. c Femalesknown to haveemerged with cubs-of-the-year. investigationsof brownbear dens in Alaska(Lentfer et al. seven dens of 10 radio-collaredbears were located on 1972, Schoen et al. 1987, Miller 1990). Den Mountainduring this study,95% (35) wereoccupied Den characteristics(elevation, aspect, construction) by females. These females rarelyventured further than of bears in various reproductivecategories varied annu- 10 km fromDen Mountain.Both males thatdenned in the ally in both areas. These variationswere not consistent areawere less than5 years old and vacatedthe areasoon and, because of data and sample size limitations, we after emergence. Unmarkedbears exhibiting denning could not correlatethem with weather or reproductive behaviorwere also observed in the area. statusof the bear. The middle reachesof BaumannCreek flow through a narrowvalley approximately150-180 m in elevation, borderedby steep, shrub-coveredsides to 610 m. Thirty Den Concentrations dens of 9 radio-collaredbears were located in this area, concentrationsof dens were found at 2 locations High 97%(29) wereoccupied by females. Movementsof these in the TerrorLake area: Den Mountainand Baumann females were generally within 10 km of the Baumann combined 1% Creek.The 2 areas comprisedonly (7.8 km2) Creek concentrationarea. Numerous unmarkedbears of the TerrorLake area,but contained36% (67/184) they were also observed denning in this area. Although the of the dens of radio-collared bears, including 40% dense vegetation and the fractured,rocky terrainoften of the dens of females and 13% (3/23) of the (64/161) precludedclose observationof actualden sites, the use of dens of males. No concentrationswere comparable naturalrock cavities for dens appearedto be greaterin the observed in Southwest Kodiak. BaumannCreek area than in other areas. Den Mountainis a 1,119 m glaciatedpeak about2 km northof TerrorRiver. Most dens were located on steep tundraslopes and barrenrock escarpmentsin north-and Fidelity to Den Sites sites west-orientedcirques. Most dens appearedto be exca- Individualbears exhibited fidelity to specific den den use vated, althoughsome naturalcavities were used. Thirty- in both study areas. Data on successive years'

parentheses). Table 7. Aspects of dens used by radio-collared brown bears in 2 study areas on Kodiak Island, Alaska, 1982-1988 (percent In

Aspect Total Study area North Northeast East Southeast South Southwest West Northwest

Terror Lake 43 (23) 35 (19) 14 (8) 12 (7) 22 (12) 29 (16) 17 (9) 12 (7) 184 Southwest Kodiak 8 (6) 21 (15) 12 (9) 24 (18) 14 (10) 21 (15) 23 (17) 13 (10) 136 Total 51 (16) 56 (18) 26 (8) 36 (11) 50 (16) 40 (13) 25 (13) 25 (8) 320 DENNINGCHARACTERISTICS OF BROWN BEARS * Van Daele et al. 263

werecollected for 74 radio-collaredbears using 162 dens. similarin bothareas. Meandistance between 1st and2nd Eighty (49%) of these dens were less than 1 km apartin den sites at TerrorLake was 1.5 km anddistances ranged successive years. Females occupied the same den site from 0.3 km to 8.9 km. In the Southwestarea the mean during2 successive seasons in 29 of these instances(8 in distance was 1.2 km (range = 0.3-2.9 km). The mean TerrorLake and 21 in Southwest). Actualuse of the same distance between 2nd and 3rd dens was 0.8 km den was suspected in all cases, but could not always be (range= 0.6-1.0; n = 2); both of these cases were in confirmed. Two females used their same den site for 5 SouthwestKodiak. consecutive winters. Fifty-three(33%) of the dens were Thirty-sixpercent (12) of these den changes involved 1 to 3 km apartand 29 (18%) were more than3 km apart single(possibly pregnant) females or females that emerged in successive years. The meandistance between individ- with COY, and63% (21) involved females with yearling ual dens in successive years was 1.9 km (range = 0.0 - or older offspring. In SouthwestKodiak, 42% (5/12) of 25.7 km). Males exhibited less fidelity to den sites the cases involved sows that emerged with 3-year-olds. (x = 7.8 km;n = 5; range= 1.3 - 20.0 km)than did females Overall,no bearschanged dens in 1982/83,1 in 1983/84, (x = 1.7 km; n = 157; range = 0.0 - 25.7 km)(P < 0.01). 6 in 1984/85, 17 in 1985/86, 8 in 1986/87, and 1 in 1987/ Meandistance between successive dens used by individ- 88. In most cases, we were not able to determine ual female bearswas similarin the 2 studyareas. Sample accuratelywhen bears moved between dens. sizes were inadequateto test differences among males. Seven males (11 instances) apparentlydid not den Radio-collaredbears occupying Den Mountainexhib- duringat least 1 of the wintersthat they were monitored. ited high fidelity to den sites. Seventy-fourpercent (20/ Theserepresented 22% (7/32) of the individualmales and 27) of the dens of radio-collaredbears in this area were 28% (11/39) of the denningperiods for males monitored within 1 km of the den used duringthe previousyear. The duringthe study. All instancesoccurred at TerrorLake, mean distance between dens of individual females in although 1 male in Southwest Kodiak may have used a successive yearswas 1.0 km (n = 25; range= 0.0-9.2 km). temporaryden for only a short time. The frequencyof Female bears denningnear BaumannCreek also exhib- non-denningdid not appearto varyannually. Three cases ited high fidelity to previouslyused den sites throughout occurredin 1982/83 and in 1983/84, 2 in 1984/85 and in the studyperiod (x = 1.6 km; n = 18;range = 0.0-2.7 km). 1986/87, and 1 in 1985/86. One beardid not den for the 3 consecutive years he was monitored,2 did not den for 2 consecutiveyears, and4 were monitored 1 Denning Anomalies duringonly denning season. radio-locationsof the non- Thirty-fiveradio-collared bears did not conformto the Sequential denningmales indicatedthey were in conventionaldenning pattern of enteringa single winter relativelysedentary mid-winter, making relatively short movements and den and remaining in that den throughoutthe winter. appearingsomewhat One bear seen bedded Includedwere 27 females (33 instances) that used mul- lethargic. undera small spruce (Picea did not awaken tiple densduring a single winter,and 7 males and 1 female sitchensis) despite repeatedclose passes with a aircraft. (12 instances)that did not occupy dens duringat least 1 fixed-wing winter. The only female that did not den lost her COY's in October 1985 within her traditionalhome near Of the females that used multiple dens in a single range BaumannCreek. She the winternear the season, 31 cases involved the use of 2 dens, and 2 cases spent village of Port several kilometers involved the use of 3 dens. No males exhibited this Lions, from her previous home range, where residents observed her in the behavior. Twenty-onecases occurredat TerrorLake and foraging landfill. She was found dead in 1986 12 in Southwest Kodiak. At TerrorLake, females that village May within 1 km of the landfill. Cause of death could not be used only 1 den duringa season occupied dens at higher determined,but she to be emaciated elevations (P < 0.1) (x = 694 m) than the initial dens of appeared and had little subcutaneousfat. females that moved dens within a season (x = 579 m). This difference was not evident in Southwest Kodiak. Characteristicsof 1st and 2nd den sites were not Mortalityat Den Sites conspicuously different. Mean elevations of 2nd den Fourradio-collared bears, all females, died at or near sites (631 m in TerrorLake and 456 m in Southwest)were theirden sites. All occurredat TerrorLake; 2 in 1984/85 somewhathigher than elevations of 1st den sites (579 m and2 in 1985/86. Two cases involvedfemales with COY in TerrorLake and 424 m in Southwest),but this differ- (0.9 yr), and 2 involved single (possibly pregnant)fe- ence was not statisticallysignificant (P > 0.1) in either males. Direct causes of mortalitycould not be deter- area. Aspects and slopes of 1st and 2nd den sites were mined. 264 BEARS-THEIR BIOLOGY AND MANAGEMENT

DISCUSSION on "averagebears" in "averageyears", a consistent pat- Winterdormancy is a complex behavioraland physio- tern of den entrancechronology is apparent. Bears in logical adaptationin response to the decreased food southcentralAlaska, with the least availablefood andthe availability and winter weather. Although numerous coldest temperaturesin late autumn,entered dens earlier authorshave described denning characteristics,knowl- than bears in areas characterizedby milder conditions. edge of whatfactors dictate when or wherea bearwill den Southeast Alaska and Kodiak have similar winter cli- is incomplete. Our investigation on Kodiak provided mates,however late autumnfood availabilityis different. additionalinformation, but even with a large sample of SoutheastAlaska has the lowest relativefood availability bears,we did not provideany specific answersas to what in the late autumnand the earliest mean entrancedates, makes bears enter dens or what is "criticalbrown bear while SouthwestKodiak has the greatestrelative availa- denninghabitat". We foundthat subpopulations of bears bility of late autumnfood and the latest mean entrance living within70 km of each otheron the same island,with dates. no real physical barriersto movement, had developed The relative timing of den emergence on Kodiak noticeably differentdenning behaviors. followed a patternsimilar to that reportedfor brown/ The relativeorder in which bearsin variousreproduc- grizzly bearpopulations in otherparts of Alaska (Schoen tive categories entered dens was similar in both study et al. 1987, Miller 1990), in the Yellowstone ecosystem areas. Femalesentered dens earlierthan most males, and (Judd et al. 1986), in Montana (Servheen and Klaver pregnantfemales frequently entered dens earlier than 1983), and in Siberia (Kistchinski 1972). Males were other bears. Onset of den entrance in both areas was generallythe 1st groupto vacate theirdens, and females gradualand not relatedto the 1st heavy snowfall, as has withCOY wereusually the last. Comparisonof meanden been reportedin the Yellowstone ecosystem (Craighead emergencedates reported for bearsin 4 areasof southern and Craighead1972). Alaska (Schoen et al. 1987, Miller 1990, this study) We found a markeddifference in mean den entrance revealedno consistentpatterns similar to those noted for dates between the 2 study areas. Females in Southwest den entrancechronology. On Kodiak,there appeared to Kodiak generally entered dens 2 to 3 weeks later than be a tendencyfor bearsto emergeearlier on the southern their counterpartsat TerrorLake. We hypothesize that part of the island than in the northernpart, but the this variationis directlyrelated to the differencesin food differencewas not significant.Weather patterns and food availabilitybetween the 2 areasduring late autumn(mid- availability may influence den emergence patterns in October through mid-December). In the TerrorLake southernportions of Alaska, but not to the same degree area, major sources of bear food were depleted by late that they influence den entrancepatterns. autumn. Herbaceous vegetation was desiccated, and Snow retentioncharacteristics are consideredto be a berries were no longer abundant. A few salmon were critical factor at grizzly bear denning sites in the Rocky availableuntil December,but most had finished spawn- Mountains(Craighead and Craighead 1972, Vroomet al. ing and had been washed to the sea by mid-October. A 1980, Servheenand Klaver 1983). Lentferet al. (1972) differentscenario occurred in SouthwestKodiak during also cited snow cover as an importantfactor on Kodiak thatsame time period(Barnes 1990). Sockeye salmon,a Island. Although most of the dens at TerrorLake were species uncommon in the TerrorLake area, were still snow-coveredthroughout the denning period,bears did actively spawningalong the shoresof the majorlakes and not appearto seek out sites thathad greatersnow depths. coho salmon were readilyavailable in several streamsin In SouthwestKodiak, it was not uncommonfor den sites SouthwestKodiak until mid-December. to have little snow cover (<1 m) throughoutwinter, and Johnson and Pelton (1980) reported considerable for some den entrancesto remainopen all winter. Schoen variationin the denningperiods of blackbears (U. ameri- et al. (1987) reportedden site characteristicson Admi- canus) across their range in North Americawith a trend ralty Island in southeasternAlaska similar to those ob- was toward longer denning periods in more northerlylati- served at TerrorLake. They speculatedthat snow tudes. These variationsresulted principally from differ- probably less importantfor insulation in south-coastal ences in the time of den entrance,and they suggestedthat Alaska, where winter temperaturesrarely fell below this was a result of harsherclimates and limited food -20 C, thanin colder interiorareas. They suggestedthat availabilityin the northernareas. A similarpattern was bears needed dry, cold sites where temperaturesgener- also evident among brown bear populationsin southern ally remainedbelow freezingand surfacewater was rare. on Ko- portionsof Alaska (Schoen et al. 1987, Miller 1990, this That hypothesis is consistent with our findings study). Althoughit is riskyto makegeneralizations based diak. DENNINGCHARACTERISTICS OF BROWN BEARS * Van Daele et al. 265

Most dens were apparentlyexcavated into hillsides or within the TerrorLake area. Den concentrationsat Den under rock outcrops. Bears frequently dug in several Mountain and Baumann Creek were in conspicuously places priorto excavatingtheir final den. Some of these differenthabitats. Female bears were able to satisfy all of exploratorydiggings may have been day beds, but most their needs in small areas in northernKodiak, and they appearedto be aborteddenning attempts, possibly aban- usually occupied relatively small annual home ranges. doned because of inadequatesoil conditions. Soil depth Sites such as Den Mountainand BaumannCreek may and stabilityappeared to be criticalfactors for denningin offer the best den site characteristicswithin the home most cases; however, snow dens and naturalcavities in rangesof severalbears and thus have disproportionately rock formationswere not uncommon. heavy use. Learnedbehavior may also play a partin den Den site characteristicswere remarkablydifferent site selection by females. Subadultfemales often remain between the 2 Kodiak study areas. Bears in the Terror in the vicinity of their mother's home range, whereas Lakearea preferred steep slopes in alpinehabitat for dens. male offspringfrequently disperse (Reynolds et al. 1987, Winter temperaturesat low and middle elevations are Miller 1987). The combination of high bear density milder and rain is more common in that area than in togetherwith learnedbehavior may result in large num- Southwest Kodiak. Bears at Terror Lake may prefer bers of females using the same denning area. alpine areas for dens because they are high enough that Althoughthe "average"bear can successfully den in a soils remainfrozen throughoutthe winter at the higher varietyof sites, the high degree of fidelity to specific den elevations. TerrorLake alpine habitat is characterizedby sites exhibited by individual brown bears on Kodiak steep, rocky crags with numerous naturalfissures and suggests a preferencefor certainsite characteristicsand/ cavities. These cragsare commonly surroundedby steep or thattradition plays a majorrole in den selection. Mean slopes thatare well-drainedand covered with sedges and distancesbetween dens of individualfemales in succes- ericaceous shrubs. The substrateis usually deep enough sive years were considerablyless in the Kodiak study to dig a den and, when frozen, stableenough for a den to areas(1.7 km) thanwere observed in southeasternAlaska retainits integritythroughout the winter. Alpine areasin (3.5 km; Schoen et al. 1987) or in southcentralAlaska SouthwestKodiak had vegetation and soil characteristics (6.1 km; Miller 1990). thatresembled those foundat TerrorLake, but the topog- Two notable anomalies in denning behavior were raphywas gentler and there were fewer rock outcrops. observedin this study;use of multipledens andfailure to In SouthwestKodiak, midslope habitatand moderate enterdens. We found little evidence thatmaternal status slopes were preferreddenning sites. Midslopehabitats in or cub age was relatedto the use of multipledens. Second Southwest Kodiak are usually on hillsides with slope dens were usually at higherelevations than 1st dens, but >30? that are vegetated with a mosaic of herbaceous site characteristicsand locations were similar.We could meadows and scatteredalder thickets. We believe they not accuratelydetermine the timingof, or the reasonsfor, provided an ecological equivalent of the steep alpine movements to 2nd dens in most cases. Most of the slopes found in the TerrorLake area. Most of the dens movements at Terror Lake appearedto coincide with found in midslope habitatwere within or at the edge of unseasonable warm and wet late autumn/earlywinter alderthickets. Alderroot systems are probably necessary periods. Some floodingof dens probablyoccurred during to stabilizedens excavated in loose, unfrozensoils (Lentfer these periods,which led to abandonment.This relation- et al. 1972). The relativelycooler, drierwinter climate, ship between weatherconditions and movement to a 2nd coupled with the laterden entrancedates, may also give den was not apparentin SouthwestKodiak. the bearsin the Southwestarea more flexibility in selec- The failureof some males to den did not appearto be tion of a dry den site with stable soils. affected by interannualvariations in food availabilityor The differencein den site characteristicsbetween the weatherconditions. Some males were active throughout 2 areasis especially interestingbecause of theirproxim- the winterduring every yearof the study. Morethan 25% ity. We suspectthat because bears in bothareas occupied of the radio-collaredmales at TerrorLake did not den small annualhome ranges,they utilizedthe most suitable during at least 1 of the winters of the study. It is not denninghabitat available within theirhome range. Suit- uncommon to see bear tracks throughout the winter able den sites were those sites thatremained dry through- months on the Kodiak archipelago. We found no pub- out the denningperiod, and provided adequate soil depth lished reportsof non-denningbrown/grizzly bears, but and for excavation stability of a den, or a suitablenatural non-denningblack bears have been reportedin Virginia cavity. and North Carolina(Hellgren and Vaughan 1987). The Adaptabilityin selection of sites was apparenteven relativelywarm winter climate and long seasonalavaila- 266 BEARS-THEIR BIOLOGY AND MANAGEMENT bility of food probablyallow some bearsto remainactive The dangerof extrapolatingdata from a denningstudy for longer periods of time on Kodiakcompared to other in 1 area to characterizedenning habitat in anotherwas portionsof brown/grizzlybear range. Non-denningbears evidenced in a reportwhich predictedthe impactsof the apparentlyspent much of their time bedded in shrubor TerrorLake hydroelectric project on brownbears (Spencer spruce microhabitatsand intermittentlytraveled rela- and Hensel 1980). In their assessment, Spencer and tively short distances within their normalhome ranges. Hensel delineateda "usabledenning habitat zone" using Althoughthese bears never entereddens, their behavior informationcollected from southern Kodiak Island (Troyer appeared to be similar to the "walking hibernation" andHensel 1969, Lentferetal. 1972). This zone included described by Nelson et al. (1983) for bears that had most of the mid-elevation(150 m to about600 m) shrub recently emerged from hibernation. No data on winter habitatin the TerrorLake area and did not encompass feeding were collected during this study, but it is sus- most of the alpine areas. Less than 40% of the dens of pected that non-denningbears reduced their food intake radio-collaredbears were within the "usable denning and may have experiencedlowered metabolism periodi- habitat"zone, and the den concentrationarea on Den cally. Mountainwas not includedin the zone. Fortunately,the impactsof the hydroelectricproject on denningwere not as as those in the assessment MANAGEMENTIMPLICATIONS great predicted pre-project because most of the impacts were in the lowland and management of a bear population re- Responsible areas(Smith and Van Daele 1990). However, an of the of the midslope quires understanding denning ecology theerror can serveas a valuablelesson thatcaution should population. Harvestrates and percentageof females in be exercisedwhen defining"critical denning habitat" for the harvestcan be affected by the timing of bearhunting any segment of the bear population. seasonsin relationto denningchronology. Knowledgeof suitable denning habitatand den concentrationareas is criticalto evaluationof potentialeffects of humanactivi- LITERATURECITED ties and developmentson the bear population. ATWELL, G., D.L. BOONE, J. GUSTAFSON, AND V.D. BERNS. OnKodiak Island, hunters harvest approximately 5.4% 1980. Brown bear summer use of alpine habitaton the KodiakNational Wildlife Int.Conf. Bear Res. of the totalbear population annually (ADF&G files). The Refuge. andManage. 4:297-305. fall hunting season (25 October - 30 November) coin- BARNES, V.G., JR. 1986. Progressreport-brown bear studies. cides with the peakperiod of den entrance,and the spring U.S. Fish and Wildl. Serv., Denver Wildl. Res. Cent., hunting season (1 April - 15 May) coincides with the Unpubl.Rep. 37pp. onset of den emergence. A limitednumber of permitsare __ . 1990. The influence of salmon availabilityon move- and of brownbears on southwestKodiak issuedto (Alaskaresidents) and guided (non- ments range non-guided Island.Int. Conf. Bear Res. and 8:305-313. hunters. Bears of eithersex are but Manage. resident) legal game, . R.B. SMITH,AND L.J. VAN DAELE. 1988. Density cubs andfemales accompaniedby cubs may not be taken. estimatesand estimatedpopulation of brownbears on By the close of the fall huntingseason, approximately Kodiakand adjacent islands, 1987. Unpubl.rep. to the 77%of the lone females and98% of the pregnantfemales Kodiak Brown Bear Res. and Hab. MaintenanceTrust. Alaska. at TerrorLake are in dens. In contrast,only about40% of Anchorage, 34pp. ANDR.J. HENSEL. 1972. brown of the females in BERNS,V.D., Radio-tracking the lone females and 70% pregnant bearson KodiakIsland. Int.Conf. BearRes. and Manage. SouthwestKodiak have entereddens by that time. This 2:19-25. suggests that females in Southwest Kodiak are more . G.C. ATWELL,AND D.L. BOONE. 1980. Brown bear available to hunters in the fall than are females in the movementsand habitat use at KarlukLake, Kodiak Island. 4:293-296. TerrorLake area. The relative of females in Int. Conf. Bear Res. and Manage. vulnerability 1957. Seasonal food habitsof the Kodiakbear. of CLARK,W.K. Southwest Kodiak is enhancedby their frequentuse Trans.North Am. Wildl. and Nat. Resour.Conf. 22:145- salmon streams during the fall hunting season, and by 149. their use of denning habitatthat is more accessible to 1959. Kodiakbear-red salmon relationships at Karluk Nat. Resour. humans(i.e., midslope habitats). This differentialvul- Lake, Alaska. Trans.North Am. Wildl. and must be taken into account when analyzing Conf. 24:337-345. nerability CRAIGHEAD,F.C., JR., ANDJ.J. CRAIGHEAD.1972. Grizzly bear harvestdata and when seasons. recommendinghunting prehibemationand denning activities as determinedby Femalesare probably equally vulnerable during the spring radio tracking. Wildl. Monogr.32. 35pp. huntingseason because emergence patterns are similar in HELLGREN,E.C., ANDM.R. VAUGHAN.1987. Home range and the 2 areas. movements of winter-active black bears in the Great DENNINGCHARACTERISTICS OFBROWN BEARS * Van Daele et al. 267

Dismal Swamp. Int.Conf. BearRes. andManage. 7:227- northcentralAlaska Range. Alaska Dep. Fish and Game. 234. Fed. Aid in Wildl. Restor. Prog. Rep. Proj.:W-22-5. Job HENSEL,R.J., W.A. TROYER,AND A.W. ERICKSON.1969. Re- 4.19R. Juneau. 59pp. productionin the female brown bear. J. Wildl. Manage. SCHOEN,J.W., L. BEIER,J.W. LENTFER,AND L.J. JOHNSON. 33:357-365. 1987. Denningecology of brownbears on Admiraltyand JOHNSON,K.G., ANDM.R. PELTON.1980. Environmental Chichagof Islands. Int. Conf. Bear Res. and Manage. relationships and the denning period of black bears in 7:293-304. Tennessee. J. Mammal. 61(4):653-660. SERVHEEN,C., ANDR. KLAVER.1983. Grizzly bear dens and JUDD,S.L., R.R. KNIGHT,AND B.M. BLANCHARD.1986. denning activity in the Mission and Rattlesnakemoun- Denning of grizzly bears in the Yellowstone Area. Int. tains, Montana. Int. Conf. BearRes. and Manage. 5:201- Conf. Bear Res. and Manage. 6:111-118. 207. KISTCHINSKI,A.A. 1972. Life historyof the brownbear (Ursus SMITH, R.B., ANDL.J. VAN DAELE. 1988. Terror Lake arctos L.) in north-eastSiberia. Int. Conf. Bear Res. and hydroelectricproject. Final reporton brownbear studies. Manage. 2:67-73. 1982-1986. AlaskaDep. Fish andGame. Kodiak,Alaska. LENTFER,J.W., R.J. HENSEL,L.H. MILLER,L.P. GLENN,AND 195pp. V.D. BERNS.1972. Remarkson denninghabits of Alaska __ , AND_ . 1990. Impacts of hydroelectric develop- brown bears. Int. Conf. Bear Res. and Manage. 2:125- ment on brown bears, Kodiak Island, Alaska. Int. Conf. 137. Bear Res. and Manage. 8:93-103. MILLER,S. 1987. Susitna hydroelectricproject final report. SPENCER,D.L., ANDR.J. HENSEL.1980. An assessment of Big game studies, Vol. 6: Black bear and brown bear. environmentaleffects of constructionand operation of the Alaska Dep. Fish and Game. Rep. to Alaska Power proposed Terror Lake hydroelectric facility, Kodiak, Authority. 276pp. (mimeo). Alaska. Brown Bear Studies and MountainGoat Studies. ___ . 1990. Denningecology of brownbears in southcentral Arctic Environ. Inf. and Data Center, Univ. of Alaska., Alaska and comparisons with a sympatric black bear Anchorage. 100pp. population. Int. Conf. BearRes. and Manage. 8:279-287. TROYER, W.A. 1961. The brown bear harvest in relation to NELSON,R.A., G.E. FOLK,JR., E.W. PFEIFFER,J.J. CRAIGHEAD, managementon the Kodiak Islands. Trans. North Am. C.J. JONKEL,AND D.L. STEIGER.1983. Behavior, bio- Wildl. and Nat. Resour. Conf. 26:460-468. chemistry, and hibernationin black, grizzly, and polar , ANDR.J. HENSEL.1969. The brown bear of Kodiak bears. Int. Conf. Bear Res. and Manage. 5:284-290. Island. U.S. Bur. of SportFish. and Wildl. Unpubl.rep. NESBITr,W.H., ANDP.L. WRIGHT.1981. Records of North 233pp. Americanbig game. Eighthed. Boone andCrockett Club. VROOM,G.W., S. HERRERO,AND R.T. OGILVIE.1980. The Alexandria,Va. 409pp. ecology of winter den sites of grizzly bears in Banff REYNOLDS,H.V., J.L. HECHTEL,AND D.J. REED.1987. Popu- NationalPark, Alberta. Int. Conf. BearRes. and Manage. lation dynamicsof a huntedgrizzly bearpopulation in the 4:321-330.