Landscape Permeability for Grizzly Bear Movements in Washington and Southwestern British Columbia

Landscape permeability for grizzly bear movements in Washington and southwestern British Columbia

Peter H. Singleton1'3, William L. Gaines2, and John F. Lehmkuhl1

1U.S. Forest Service, Pacific NorthwestResearch Station, 1133 NorthWestern Avenue, Wenatchee WA98801, USA 2U.S. Forest Service, Wenatchee NationalForest, 215 MelodyLane, Wenatchee WA98801, USA

Abstract: Providingopportunities for grizzly bears (Ursus arctos) to move between blocks of habitat is importantfor the long-termconservation of grizzly bearpopulations. While the particularsof grizzly bear habitat selection during long-distance movements are poorly understood, some landscape characteristicssuch as road density and land cover type are correlatedwith grizzly bear habitatuse at various scales. We compiled digital maps of roads, human populationdensity, land cover class, and topography to evaluate the resistance of the year 2001 landscape to grizzly bear movement in WashingtonState and adjacentportions of Idaho and British Columbia (BC). We developed habitat associationand dispersalhabitat suitability models based on publishedliterature and used geographic informationsystem (GIS) weighted-distanceand least-cost analysis techniquesto evaluate landscape permeabilityfor grizzly bear movement. Our analysis identified 5 blocks of potential grizzly bear habitat in Washington and adjacent areas, including the Columbia-Selkirk Mountains, the North Cascades, the CentralCascades, the South Cascades, and the Coast Range. We evaluated landscape permeability between these habitat blocks and highlighted potential linkage areas. Our models indicatedthe Stevens Pass fracturezone between the North and CentralCascades blocks was the most permeable,followed (in orderof relativepermeability) by the Fraser-Coquihallafracture zone between the North Cascades and the Coast Range, the Okanogan-Kettle fracturezone between the North Cascades and the Columbia Mountains,and the SnoqualmiePass fracturezone between the Central and South Cascades. This evaluation provides a consistent measure of the expected potential for grizzly movement across a broadlandscape that can be used to target areas for finer-scaleevaluation and help identify landscapemanagement priorities at a regional scale.

Key words: grizzly bear, habitat modeling, highways, landscape connectivity, meta-population,North Cascades Ecosystem, Ursus arctos

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Maintainingopportunities for animalsto move across demographicfluctuations (McCullough 1996). This is broad landscapes is an importantconservation consid- a particularly important consideration for long-lived eration for some sensitive wildlife species (Noss and species with large spatial requirements and low re- Cooperrider1994). Most animals are not uniformlydis- productive rates, such as grizzly bears (U.S. Fish and tributed across large landscapes. They occur in pop- Wildlife Service [USFWS] 1993, Weaver et al. 1996) ulations or subpopulationscentered on areas of suitable and other large carnivores(Beier and Loe 1992, Noss et habitat.Depending on the species and the characteristics al. 1996, Dobson et al. 1999, Edelmann and Copeland of the landscape between habitat patches, groups of 1999, Pierce et al. 1999, Reudiger et al. 2000). populationsmay function as a meta-population(McCul- Maintenanceand restoration of landscapepermeability for lough 1996). Providing animals opportunitiesto move is a particularlyimportant consideration ecosystems across broad landscapes in a functioning meta-popula- such as the North Cascades, which support relatively to be tion can mitigate negative effects of genetic isolation, small populations of grizzly bears and are likely random disturbances (such as fire or storms), and isolated from other populations (USFWS 1997, North CascadesGrizzly Bear Recovery Team 2001, Servheenet al. 2003). Substantialeffort has been expendedto assess [email protected] landscape permeabilityfor grizzly bears in the Rocky

90 LANDSCAPEPERMEABILITY FOR GRIZZLYBEARS * Singleton et al. 91

Mountains(Servheen and Sandstrom1993, Meitz 1994, populationin the Canadianportion of the NorthCascades Boone and Hunter 1996, Walker and Craighead 1997, Ecosystem consists of 17-23 adult and subadultgrizzly Servheen et al. 2003), but permeability has not been bears, including 5-6 reproductive females. The U.S. assessed in and aroundthe North CascadesEcosystem. portionof the North CascadesEcosystem is a designated Prior to Anglo-American settlement, grizzly bears grizzly bearrecovery zone (USFWS 1997). The Canadian were distributed through much of western North portionof the ecosystem is an areaof specialmanagement America. By 1970 grizzly bears remained in only 2% emphasisfor grizzly bears (NorthCascades Grizzly Bear of theirformer range within the contiguousUnited States RecoveryTeam 2001). Currentmanagement activities for (USFWS 1993, Servheen 1999). Though numbershave grizzly bears in the North Cascades Ecosystem are increased since their listing under the Endangered reviewed by Gaines et al. (2000 and 2001). Species Act (16 U.S. Code 1531-1544) in 1975, the While physicallycapable of long distancemovements, current distributionof grizzly bears in the contiguous grizzly bears do not frequentlymake such movements, United States is restricted to the Northern Rocky particularlyin the fragmentedhabitats of the northwest- Mountains, the Selkirk Mountains, the Cabinet-Yaak ern United States and southwesternCanada (McLellan Ecosystem, the Yellowstone Ecosystem, and the North andHovey 2001, Servheenet al. 2003). Adult male home CascadeEcosystem (USFWS 1993, Mattsonand Merrill ranges of grizzly bears in North America are 500-2,500 2002). Maintenanceor restorationof connectivity both km2 (M.N. LeFranc, M.B. Moss, K.A. Patnode, and within and between these remnantpopulations is a key W.C. Sugg, 1987, Grizzlybear compendium, Interagency conservationconcern for grizzly bears (Servheen et al. Grizzly Bear Committee, Missoula Montana, USA), 2003) and was explicitly identified in the Grizzly Bear indicatingthe ability to move long distances. However, Recovery Plan for the United States (USFWS 1993). McLellanand Hovey (2001) found thatthe averagenatal Grizzly bears have been and continue to be presentin dispersal distance of grizzly bears in the Rocky the North Cascades Ecosystem in Washington and Mountains near the U.S.-Canadian border was 30 km southernBritish Columbia (Bjorkland1980; Almack et for males (n = 18) and 10 km for females (n = 12). al. 1993; P.T. Sullivan, 1983, A preliminarystudy of Maximumdispersal distances were 67 km for a male and historic and recent reportsof grizzly bears in the North 20 km for a female. They stated,"Our results suggest that Cascadesarea of Washington,Washington Department of meta-populationreserve designs must provide corridors Game, Olympia, Washington, USA). Grizzly bear wide enough for male grizzly bears to live in with little numbers in the North Cascades Ecosystem were sub- risk of being killed" (McLellanand Hovey 2001:838). stantiallyreduced following Euro-Americansettlement as Several models have been developed that evaluate a result of intensive killing for the fur trade and for habitat suitability or habitat effectiveness for grizzly predatorreduction, followed by rapid human encroach- bears (Clevengeret al. 1997, Mace et al. 1999, Merrillet ment into grizzly bear habitat (Sullivan unpublished al. 1999, Carrollet al. 2001). Other modeling applica- report 1983, Almack et al. 1993). Sullivan (unpublished tions evaluatedhabitat linkages and potentialmovement report 1983) documented425 grizzly bear hides taken routes for grizzly bears. Servheenand Sandstrom(1993) around the Cascades between 1846 and 1851. Small developed a model to identify grizzly bearlinkage zones numbers of grizzly bears continue to be present in the incorporatingroad density, distance to developments, North Cascades Ecosystem. Almack et al. (1993) docu- hiding cover, and riparianhabitat. This model has been mented 20 confirmedgrizzly bear observationsscattered applied in a numberof areasin the Rocky Mountainsof throughout the U.S. portion of the North Cascades Montana, Alberta, and British Columbia (Mietz 1994, Ecosystembetween 1967 and 1991 (including9 locations Sandstrom1996, Apps 1997, Servheen et al. 2003). of grizzly beartracks, 1 food cache, 6 visual observations, Boone and Hunter(1996) designed a diffusion model and a grizzly bear that was killed in 1967). L.W. Gyug to evaluate landscape permeability in the Northern Forest (1998, development plan blue-listed species Rockies, using land cover and ownership to calculate for inventory mammals: assessment of grizzly bear resistance to movement. Walker and Craighead(1997) habitat use and populations, timber harvest mitigation conducted least-cost corridor analysis to highlight in the strategies North CascadesGrizzly Bear Population potential movement corridors for grizzly bears in the British British Unit, Columbia; Columbia Ministry of Rocky Mountains.Their model incorporatedvegetation Southern Environment, Interior Region, Kamloops, type, edge length, and road density as predictors of British Columbia,Canada) evaluated grizzly bear detec- landscape permeability. Kobler and Adamic (1999) tions andhabitat conditionsand estimated that the current developed a decision tree model from bear sighting

Ursus 15(1) WorkshopSupplement:90-103 (2004) 92 LANDSCAPEPERMEABILITY FORGRIZZLY BEARS * Singleton et al. locations and least-costpath analysis to predictEurasian East of the Cascade Range, relatively arid conditions brown bear movement relativeto highways in Slovenia. dominate the agriculturaland shrub-steppe landscapes Model parametersidentified from theiranalysis included of the interior Columbia Basin. These ard conditions percentforest cover, humanpopulation density, proxim- extend north along the Okanogan Valley into central ity to settlements,elevation, and forest type. British Columbia. This broad valley provides some of Based on our evaluationof previouslinkage modeling the most temperateconditions in all of Canada and is efforts, we developed a modeling approachthat would: known for its agricultureand retirementcommunities. (1) facilitatea multi-speciesanalysis; (2) explicitly iden- Northernportions of the OkanoganValley are heavily tify populationsource areas and resistanceto movement developed, particularlyalong OkanaganLake where the between them; (3) evaluate the cumulative effects of cities of Penticton, Kelowna, and Vernon are located. movementroutes landscapebarriers to identify potential East of the Okanogan Valley in British Columbia and and a consistent measure that obstructions;(4) provide northeasternWashington, the Kettle and Selkirk Moun- could be used for of the ranking portions landscape tain Ranges extend south from the ColumbiaMountains insteadof placing artificialcorridor boundaries on a map; to the Columbia River at Grand Coulee and the Pend and an intuitive thatcan be (5) provide graphicalproduct Oreille River north of Spokane. These low mountain used to communicatethe and resultsto problem analysis ranges are characterizedby interior mixed coniferous individuals with diverse The we backgrounds. analysis forest, and the U.S. portions are largely within the one of a broader multi- present here emphasizes part Colville and Idaho PanhandleNational Forests. Wildlife et al. 2001, 2002). species analysis (Singleton habitat conditions are described for Washington by Johnson and O'Neil (2001) and more specifically for grizzly bear by Gaines et al. (2000, 2001). Habitat Study area conditions in British Columbia were reviewed by the The analysis of Singleton et al. (2002) addressed North Cascades Grizzly Bear Recovery Team (2001). landscape permeability for large carnivores in Wash- ington and adjacent portions of Idaho and British Columbia (Fig. 1). The analysis evaluated from the Oregon-Washington border north to Revelstoke and Methods British and from the Pacific Coast Kamloops, Columbia, Our analysis included 3 steps: to the Idaho-Montana an area of east border, 325,667 1. we identifiedconcentrations of grizzly bear habitat km2. Results here the of presented emphasize portion using a regional model, that area to the evaluation of pertinent landscape 2. we evaluated landscape barriers to movement for bears. In we focus permeability grizzly particular, aroundhabitat concentrations, and on the CascadeMountain northof Mount Rainier Range 3. we evaluated the potential for animal movement northeastern and National Park, Washington, adjacent between habitatconcentrations. of British Columbia and Idaho. portions We used ArcInfo GIS (version 8.1, Environmental The of the largely defines broad- gross geology region Science Research Institute [ESRI] 2001) to assemble scale landscapepatterns in the study area. In particular, regional GIS maps of road density, human population the crest of the Cascade Range runs from the Columbia density, land cover, and slope (Table 1, base maps and River east of Portland,Oregon, into British Columbia complete metadata are available in Singleton et al. east of Vancouver, meeting the Coast Range along the We data that was suitable for mapping FraserRiver in southernBritish Columbia. These moun- 2002). compiled at a 1:100,000 to 1:250,000 scale. Because the analysis tain substantiallyinfluence the climate, vegeta- ranges area state and national boundaries, we com- tion, and humandevelopment in the region. West of the spanned bined 2 or more data sets for each layer. We used a 90- Cascade Range, moist coastal conifer forest and urban meter rastercell size for our analyses. development characterizethe landscape of the Puget We identified areaswith concentrationsof Lowlands. SouthwesternWashington and the Olympic highlighted bear habitat a model that identified core Peninsula are also characterizedby moist coniferous grizzly using areas with low levels of human disturbance(Puchlerz forest, much of which is in private ownership and and Servheen We identified all roadless areas managed for timber production.The Olympic National 1994). with a mix- Parkand some surroundingnational forest lands provide (road density <0.01 miles per squaremile) an isolated block of less disturbed forest and alpine ture of forest-mesic shrub or alpine edge landcover habitaton the Olympic Peninsula. types. We qualitatively identified the largest polygons

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Study Area

States and Provinces Highways

Multi-Species Analysis Extent Scale Y2 AreaPertinent to GrizzlyBears 0 25 50 75 100 Km S

Fig. 1. Area evaluated for landscape permeability for grizzly bears in Washington and adjacent portions of British Columbia (southwestern Canada) and Idaho (northwestern USA), 2001. Ursus 15(1) WorkshopSupplement:90-103 (2004) 94 LANDSCAPEPERMEABILITY FORGRIZZLY BEARS * Singleton et al.

Table 1. Base maps and data sources used to evaluate landscape permeabilityfor grizzly bears in Washington and adjacent portions of Idaho (USA) and British Columbia (Canada), 2001. Landscape characteristic Datafor Washington Datafor BritishColumbia Landcover WashingtonGAP Project1991 LandCover BritishColumbia Baseline ThematicMapping (30 meter raster,about 1:100,000 (BTM)and BiogeoclimaticSubzone/Variant scale) (Cassidy 1997) Mapping(30 meter raster,about 1:250,000 scale) (BCMELP1998) Humanpopulation U.S. Census Bureau1990 population StatisticsCanada 1989 populationby electoral density by census blockand Land districtand BritishColumbia Ministry of Ownership(1:100,000 scale) Environment,Lands, and Parks (BCMELP) (Quigleyet al. 2001) AlienatedLands map (1:500,000 scale) (StatisticsCanada 1989, BCMELP1997) Road density WashingtonDepartment of Natural BritishColumbia Terrain Resource Resources (WSDNR)Transportation InventoryMapping Transportation Data 1998 (1:24,000 scale) Data Layer(1:20,000 scale) (WSDNR1998) (BCMELP1996) Slope DigitalTerrain Model (90 meter) DigitalTerrain Model (25 meter (Quigleyet al. 2001) resampledto 90 meter) (BCMELP1999)

with the highest concentrations of these habitat where m is the cell size in meters (90 for our analysis). conditions as source areas between which we mapped Where s = 1, cells were assigned a weighted-distanceof the minimumdistance across the cell. landscapepermeability (Singleton et al. 2002). 90 meters, identified "availableareas" as those accessible to We conductedweighted-distance analysis to evaluate We intra-territorialmovements for animals within cumulativeeffects of landscapebarriers between grizzly regular, habitatconcentrations affected least by landscape bear habitatconcentrations. Weighted-distance analysis (areas barriers)by highlightingareas within 100 km weighted- assigns each map cell a c value thatrepresents resistance distance of a habitatconcentration area. The landscapes to movement,or cost of moving acrossthat cell, based on we described as available areas were portions of the cell characteristics (ESRI 1992:6-63 to 6-78). The with few barriers for bears moving from between each cell and the nearest landscape weighted-distance map habitatconcentrations. That these areashad few barriers habitatconcentration was calculatedas the sum of c for for bear movementdid not necessarilyindicate that they all the cells the route between that cell along least-costly were suitable habitat for grizzly bears in the sense of and the most accessible habitatconcentration. Map cells providing food, denning sites, or other life history with values had more landscape high weighted-distance requisites. barriersbetween them and the nearest habitat concen- Areas between habitatconcentrations with barriersto trationthan cells with low weighted-distancevalues. movement were identified by highlighting areas dis- habitat We developed an index of dispersal suitability playing a 100-1,000 km weighted-distancefrom habitat (s) from literatureand expert opinion to calculate c for concentrations. We refer to such areas as "fracture each cell (Singleton et al. 2002). Dispersal habitat zones" (Servheen and Sandstrom 1993). We assumed suitabilityranged from 0 (low permeability,most costly) that areas >1,000 km weighted-distancefrom a habitat We to 1 (most permeable,least costly), and was calculatedas concentrationwere inaccessible to grizzly bears. conductedleast-cost corridor analysis within the fracture s = cover class) X (Ppopulationdensity) (Pland zones to map the portions of those landscapeswith the x (Proad density) X (Pslope) fewest barriersto animalmovement. Least-cost corridor analysis attributeseach map cell with the total cost of where P is the value for each landscape permeability moving between 2 habitat concentrations along the characteristicat that cell (Table 2). The cost (c) of mov- least-costly route throughthat cell. The most permeable across each cell was calculatedas ing portions of fracture zones were identified by stratify- 10 that c (m(100( - s))) ing the fracture zone into equal-area groups representedthe most permeable10% of the fracturezone

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Table 2. Values for habitat characteristics and permeability (P) for the grizzly bear dispersal habitat suitability index for Washington and adjacent parts of Idaho, USA, and British Columbia, Canada, 2001. Humandensity Roaddensity Slope Land cover (people/square mile) (miles/square mile) (degrees) Class Value Class Value Class Value Class Value alpine 1.0 <10 1.0 <1 1.0 <20 1.0 coastal mesic forest 1.0 11-25 0.5 1.1-2 0.8 21-40 0.8 dry forest 1.0 26-50 0.3 2.1-4 0.5 >40 0.6 interiormesic forest 1.0 >50 0.1 4.1-6 0.3 wetland-riparian 1.0 6.1-10 0.2 coastal mesic shrub 0.8 >10 0.1 interiormesic shrub 0.8 dry shrub-grass 0.5 agriculture 0.3 bare ground 0.3 snow-ice 0.1 urban-developed 0.1 water 0.1 landscape(corridor value 1) to the least permeable 10% USA, and U.S. Fish and Wildlife Service, Missoula, of the fracturezone landscape(corridor value 10) based Montana, USA) and the designation of the area as on the least-cost corridorvalue. a recovery zone (USFWS 1993), we felt that it was appropriateto incorporatethis area into our analysis of landscapepermeability for northeasternWashington. We Results accomplished this by appending forested, roadless Five habitatconcentration areas were identifiedbased polygons in the Selkirksto the modeled habitatconcen- on our habitat association models for grizzly bears trationmap. (Fig. 2). Ourmodeling indicatedthat the North Cascades The dispersalhabitat modeling indicatedthat approxi- habitat concentrationarea extended from Manning and mately 36% of the analysis area (Washington and CathedralProvincial Parks (south of BC Highway 3), adjacentportions of Idaho and British Columbia) was south to the vicinity of Glacier Peak and Lake Chelan relatively good dispersal habitat (total permeability (northof U.S. Highway 2). The BC Coast Range habitat value >0.6), approximately23% of the analysis area concentrationarea was northwestof the North Cascades. was moderatedispersal habitat (total permeabilityvalue The Coast Range habitat concentrationis contiguous 0.3 to 0.6), and 41% of the analysis area was poor with occupied grizzly bear habitat extending north dispersal habitat (total permeability value <0.3). The throughcoastal British Columbia and Alaska. weighted-distanceanalysis delineatedbroad portions of East of the North Cascades,the Columbiaand Selkirk southern British Columbia, northernWashington, and Mountains habitat concentration also is contiguous the Cascade Range as being within the 1,000 km with occupied grizzly bear habitatto the north. South of weighted-distance that may be accessible for long- the North Cascades, our model identified the Central distance bear movements (Fig. 2). Most of south- Cascades (mostly within the Alpine Lakes Wilderess eastern Washington and western Washington were Area) and the South Cascades (near Mount Rainier beyond 1,000 km weighted-distancefrom any habitat National Park and the Norse Peak and Goat Rocks concentration.We expect that those areas beyond 1,000 Wilderness Areas) as habitat concentrationareas. The km weighted-distanceare inaccessible to any kind of grizzly bear habitat association model did not identify movement by grizzly bears. habitatconcentrations in the SelkirkRange in Washington Available area (those areas within 100 km weighted- and Idaho because roadless area polygons there were distance of habitat concentrations) surrounding the relatively small. However, due to the documented North and CentralCascades habitat concentrationsen- presenceof grizzly bearsin the Selkirks(W.L. Wakkinen, compassed 23,887 km2 (Fig. 2). This area with few and W. Kasworm, 1996, Grizzly bear and road density barriers connected the North and Central Cascades relationshipsin the Selkirk and Cabinet-Yaakrecovery habitatconcentrations near Stevens Pass but had a sub- zones, IdahoDepartment of Fish andGame, Boise, Idaho, stantialbottleneck along U.S. Highway 2. Although the

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HabitatConcentrations and Weighted-DistanceResults Highways [-1] States and Provinces Weighted-Distance 0 - 100 (Available) _ 101 -500 Scale 501 - 1000 (Least Accessible) 0 25 50 75 100 Km fi HabitatConcentrations and Available Areas Mii

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urbanland uses often defined the limits of habitatcon- Table 3. Landscape permeability within fracture zones identified for grizzly bears in Washington, centrations,areas accessible for grizzly bearmovements, USA, and adjacent portions of British Columbia, and landscapebarriers within fracturezones. In general, Canada. our analysis identified habitat concentrationsand adja- Minimum Ratio of cent availableareas located in montaneforest habitatson linkage weighted- public lands. Fracturezones were generally located in weighted- Actual distance: majorvalleys or mountain where distance distance actual passes majortranspor- tation human Fracturezone (km) (km) distance routes, developments, and natural tran- sitions in habitat occurred. Stevens Pass 84 25 3.3 type The Fraser-Coquihalla 348 23 14.7 major habitatconcentrations and adjacentavail- Okanogan-Kettle 598 162 3.7 able areas identified by our models correspondwell to SnoqualmiePass 760 42 17.9 the documented distribution of grizzly bears in our analysis area. The North and Central Cascades habitat concentrationsand adjacent available area corresponds to the North Cascades Ecosystem Grizzly Bear Re- area aroundStevens Pass was within 100 km weighted- covery Area (USFWS 1997). These areas also corre- distanceof habitatconcentrations and did not quite meet spond well to the distributionof confirmedgrizzly bear our definitionof a fracturezone (Table 3), we conducted observations recorded by Almack et al. (1993). Our least-cost corridor analysis throughthe area because we modeled habitat concentration and adjacent available were interested in the exploring habitat connectivity area for the Coast Range corresponds to the Stein- the bottleneck U.S. patternsthrough along Highway 2. Nahatlatchand Garibaldi-PittGrizzly Bear Population Available area the South Cascades habitat surrounding Units, which supportthreatened populations of grizzly concentration km2. Available encompassed 5,155 area bears (North Cascades Grizzly Bear Recovery Team the Coast and Columbia Mountains surrounding Range 2001). These population units (through adjacent units and km2, encompassed24,481 36,217 respectively.The with threatenedstatus) are contiguous with the Klina- Coast and Columbia Mountains are Range both conti- klini-Homathko and Knight-Bute units, which have with bear habitat guous occupied grizzly extending viable statusand are approximately200 km farthernorth north the extent of our beyond analysis. and west through the Coast Range (North Cascades identified Weighted-distanceanalysis 3 majorfracture Grizzly Bear Recovery Team 2001). Our Columbia zones between habitat in addition to concentrations, Mountains habitat concentration corresponds to the Stevens Pass (Table 3, Least-costcorridor anal- Fig. 3). Valhalla, Central Selkirk, and South Purcell Grizzly ysis indicated that Stevens Pass the Central (between Bear PopulationUnits, which supportviable populations and North Cascades habitat was the concentrations) of grizzly bears and are contiguous with viable most fracture followed the Fraser- permeable zone, by populationsextending north throughthe Columbia and Coquihalla(between the North Cascades and the Coast Rocky Mountains (North Cascades Grizzly Bear Re- Range), Okanogan-Kettle(between the North Cascades covery Team 2001). The South Cascades was the and the Columbia only Mountains), and Snoqualmie Pass area modeled as a habitat concentrationthat does not (between the Centraland South Cascades). have recent documentationof at least occasional grizzly bearpresence. This is a relatively small area (5,155 km2 within 100 km weighted-distanceof the habitatconcen- Discussion tration)with substantialhuman activity. This areais well Ourweighted-distance and least-costcorridor analysis below the 20,000 km2 identifiedby Mattsonand Merrill several highlighted common featuresdefining landscape (2002) as characteristicof landscapesthat have recently permeability.Major transportation routes and associated supportedgrizzly bears in the contiguous United States.

j 2. Fig. Grizzly bear habitat concentrations and results of the weighted-distance of the cumulative effects of analysis landscape barriers to grizzly bear movement in Washington and Idaho, USA, and British Columbia, 2001. Canada, Darker areas have fewer barriers for grizzly bears moving from the modeled habitat concentrations.

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Majorhighways pass througha matrixof grizzly bear routes over the Cascade Mountains. Because develop- habitatin all of the modeled habitatconcentrations and mentsalong this transportationroute are generally limited adjacentavailable areas (Figs. 2, 3). U.S. Highway 20 to small recreationcabins, this landscape is relatively over Washingtonand Loup Loup Passes, BC Highway permeable,although levels of permeabilitycould decline 3 in the vicinity of Manning Provincial Park, and WA as trafficvolumes andrecreational developments increase SR 542 near Mount Baker pass through the North along the highway. Cascades habitat concentrationand adjacent available Fraser-Coquihalla Fracture Zone. Our model areas.U.S. Highway 97 over Blewett Pass intersectsthe showed 2 potential linkages between the Coast Range Central Cascades habitat concentration and adjacent and the North Cascades. The shorterroute passes from available areas. U.S. Highway 12 around White Pass, the North Cascades, northwestof Ross Lake, across the WA SR 410 near Chinook Pass, and WA SR 123 FraserRiver between Chilliwackand Hope, and into the through Mount Rainier National Park pass through CoastRange east of HarrisonLake (Fig. 3). This is a short, the South Cascades habitat concentrationand adjacent 24-km linkage between modeled habitatconcentrations, availableareas. BC Highway 99 between Squamishand butit has poor landscapepermeability (weighted-distance Lilooet intersectsthe Coast Range habitatconcentration 349 km, weighted to actual distanceratio of 14.5). Poor and adjacent available areas. BC Highway 3 around permeabilityis due to the Trans-CanadaHighway on the KootenayPass, BC Highway 3a east of Nelson, and BC south side of the Fraser River (a 4-lane, divided Highway 6 from Salmo to Nakusp pass throughhabitat highway), BC Highway 7 on the northside of the Fraser concentrations and adjacent available areas in the River, a 300-m water crossing through the river, and Selkirk and Columbia Mountains. These routes could moderateto high humandensity in the valley bottom.The limit movements within landscapes that could support second route connects the northernportion of Manning grizzly bears and may contributeto factors that limit ProvincialPark to the Stein-Nahatlatcharea by passing resource availabilityand increase mortalityfor resident north of CoquihallaSummit and throughthe Anderson bears (Noss et al. 1996, McLellan et al. 1999). River drainage. This route is substantially longer, Landscapes in the Coast Range and Columbia Moun- approximately150 km, but has betteroverall permeabil- tains also showed some evidence of substantialnatural ity (weighted-distance 474 km, weighted to actual barriers within habitat concentrationsassociated with distanceratio of 3.1). Factorslimiting permeability along Upper Arrow, Lower Arrow, and KootenayLakes in the this linkageinclude the FraserRiver (a large,fast-moving Columbia Range and extensive glacial systems in the river in a rugged canyon), the Trans-CanadaHighway (a Coast Range. 2-lane highwaythrough the FraserRiver Canyon) and the Stevens Pass Fracture Zone. With a minimum CoquihallaHighway (BC Highway 5, a 4-lane divided has been weighted-distanceof 84 km, the Stevens Pass area did highway). Much of the Coquihalla highway not meet our 100 km weighted-distancecriterion to be equipped with game fencing to reduce animal-vehicle considered a fracture zone. However, the weighted- collisions. Severalunderpasses provide animal crossings; character- distance map indicated a bottleneck in landscape however, these structuresmay not have the bearsin other permeabilitythrough this area, so we included it in our istics of crossing structuresused by grizzly least-costcorridor analysis. The areaeast of Stevens Pass areas (Clevengerand Waltho 2000). 2 had the best potentialfor landscapepermeability between Gyug (unpublishedreport 1998) described grizzly the North and Central Cascades. Several features bears that were relocated into the BC portion of the in the Fraser- contributeto reduced permeabilitythrough the Stevens North Cascades ecosystem and traveled In June 1994 a female was Pass landscape, including a large ski area at the pass, Coquihalla fracturezone. of residential developments along U.S. Highway 2, and releasedin the AndersonRiver area(north Coquihalla in 1995 near rugged terrain.U.S. Highway 2 is a 2-lane undivided Summit) and recaptured May Agassiz River from a movementof highway and is 1 of 3 major east-west transportation (acrossthe Fraser Chilliwack,

Fig. 3. Fracture zones and results of the least-cost corridor analysis of the cumulative effects of landscape barrierson grizzly bears moving between modeled habitat concentration areas in Washington and Idaho (USA) and British Columbia (Canada), 2001. Darkerareas have fewer barriers for grizzly bears moving between the modeled habitat concentrations.

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Fracture Zones and Least-Cost Corridor Results

Highways i[_- States and Provinces \W HabitatConcentrations and Available Areas Value Linkage Scale 1 (Best) 2 -3 0 25- 50 75 100 Km _ 4 - 5 (Moderate) I __N

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approximately30 km). In October 1992 a male was the ColumbiaRiver, across WA SR 20 at ShermanPass, released in the Pasayten River area on the east side of then west across WA SR 21 along the Sanpoil River, Manning Provincial Park. It moved about 64 km west across U.S. Highway 97 near Riverside, and into the to the Chilliwack River that fall, then returnedto its North Cascades northwestof Conconully (Fig. 3). This originalcapture area in the Coast Range near Pemberton linkage was stronglychanneled to the east by substantial by June 1993 (a cumulative movement of at least 260 landscape barriersalong BC Highway 3, just north of km total distance). Both bears were detected near the the internationalborder, between Osoyoos and Grand linkage identified by our model near Chilliwack and Forks. Agriculturalland uses, high human population Hope (Gyug unpublishedreport 1998). density, and associatedurban areas combined to channel Okanogan-Kettle Fracture Zone. The best link- the modeled linkage into the vicinity of ChristinaLake ages between the North Cascades and the Columbia and along the crest of the Kettle Range. Mountainspassed through the Okanogan Valley south Snoqualmie Pass Fracture Zone. Several fac- of Kelowna and Penticton (Fig. 3). Both linkages tors limit permeability through the Snoqualmie Pass involve long water crossings (>1 km) throughOkana- landscape. These include a major interstate highway gan or Skaha Lakes. We expect that functionality of (Interstate90 [I-90]), extensive recreationand residential these linkages may be limited by the long water cross- development, fragmented forest cover resulting from ings. Our models also identified 2 terrestriallinkages checkerboardfederal-private land ownership, 3 large throughthe OkanoganValley; one throughthe Canadian lakes, and rugged terrainalong the crest of the Cascade portionof the valley at Vaseux Lake ProvincialPark and Mountains.Interstate 90 probablyreduces permeability the other through the U.S. portion of the valley near throughthis areamore thanother features (Singleton and Riverside, between Omak and Tonasket. The Vaseux Lehmkuhl 1999). It is the primary east-west trans- Lake linkagepasses from the habitatconcentration in the portation route across the Cascades into Seattle and Monashee Mountains, through the Kettle and Granby carries an average of 25,000 vehicles a day, with peak watersheds, across BC Highway 33 along the West volumes exceeding 58,000 per day (Washington State Kettle River, across BC Highway 97 at Vaseux Lake, Department of Transportation 2003). Our models through the Similkameen River valley north and west highlighted a primary linkage area approximately35 of Cawston, and connects with the North Cascades km east of Snoqualmie Pass, near Easton Lake State near CathedralProvincial Park. This is a long linkage Park. This linkage extends from the Central Cascades (approximately160 km from the Columbia Mountains habitat concentrationin the Alpine Lakes Wilderess to the North Cascades); however, grizzly bears are Area, across 1-90 at Easton Hill, to the South Cascades presentwithin this linkage in the Kettle-GranbyGrizzly habitatconcentration in the Norse Peak WildernessArea Bear PopulationUnit (statusthreatened, North Cascades and Mount Rainier National Park (Fig. 3). The linkage Grizzly Bear Recovery Team 2001) and are occasionally identified by our modeling correspondsto the primary reported moving into the Canadian portion of the linkage area along 1-90 identified by finer scale OkanoganValley (M. Austin, British Columbia Minis- modeling for multi-species landscape permeabilityand try of Land, Air, and WaterProtection, Victoria, British field surveys reported by Singleton and Lehmkuhl Columbia, Canada,personal communication,2002). In (1999). the 1997 a 5-year-old male grizzly bear was killed near The Snoqualmie Pass landscape is unique for Vaseux Lake, and in 1999 a 4-year-old male was killed attention it has received regarding management to northeast of Penticton (British Columbia Ministry of restore habitat connectivity for a variety of species. Land, Air, and Water Protection, Victoria, British This landscape was designated as an adaptivemanage- Columbia, Canada, unpublished data). It is also note- ment area under the Northwest Forest Plan (U.S. worthy that the distance from the North Cascadesto the Department of Agriculture Forest Service [USFS] was to closest viable population unit in the Columbia Moun- 1997). The primary management objective with tains (the Valhallaunit) is 150 km, while the distanceto restore habitat connectivity for species associated habitat the closest viable population unit in the Coast Range late successional forest. Recent land exchanges, (the Klinaklini-Homathkounit) is 290 km. acquisitions,and activities by non-governmentalorgan- connectiv- The other linkage between the North Cascades and izations (NGOs) focused on restoringhabitat also the ColumbiaMountains passes from the Valhalla area, ity through the area (USFS 1999), which was south across BC Highway 3 east of Christina Lake, a primaryobjective of a large highway reconstruction in this across U.S. Highway 395 into the Kettle Range west of projectplanned along 1-90. Though the emphasis

Ursus 15(1) WorkshopSupplement:90-103 (2004) LANDSCAPEPERMEABILITY FORGRIZZLY BEARS * Singleton et al. 101 area has not been on restoring habitat connectivity available habitat in our analysis (areas within which specifically for grizzly bears, the coordinationbetween movement is not restrictedby substantialbarriers) are land managementagencies, NGOs, and the Washington not necessarily suitable habitat. Departmentof Transportationin managingthe Snoqual- While the information presented here focuses on mie Pass landscapemay provide a positive example for grizzly bears, this approach can evaluate landscape land management emphasizing habitat connectivity in patternsfor many species, identifying common patterns other areas. for those species and developing viable multi-species plans. The majorityof the linkages presentedhere were also identified as potential linkages for other large Conclusion carnivores(Singleton et al. 2002). The products of our approachcan contributeto the Successful managementof broad-scale habitat link- managementof habitatconnectivity in a varietyof ways. ages for large carnivores will require cooperation These products can be used to communicate issues between resource managementagencies, local govern- associated with habitatconnectivity, including identify- ments and planningboards, NGOs, transportationagen- ing areas where habitatconnectivity may be an appro- cies, public utilities, local citizens, and stakeholder priate management objective and highlighting factors groups.Planning will need to integrateland management that could influence connectivity in those areas. We across jurisdictionaland ownershipboundaries through view this analysis as hypothesis development in which a variety of creative mechanisms (Knight and Landres we propose that the linkage areas we identify are more 1998). Products like those presented here can help likely to provide for successful passage for grizzly bears facilitate communicationbetween these diverse groups than adjacent areas, based on the landscape character- and contributeto the developmentof common goals for istics we evaluated.These hypotheticallinkages need to landscapeplanning. be investigatedmore thoroughlythrough the analysis of higher-resolutionGIS data and field surveys. We have attemptedto develop a method that expli- Acknowledgments citly estimates landscape permeability.These estimates This analysis was funded by the Washington State can be used to comparelandscape permeability between Departmentof Transportationand U.S. Departmentof different areas at various scales. However, the actual Agriculture Forest Service, Northwest Forest Plan. of the functionality linkage areaswe identify can only be We acknowledge P. Wagner and M. Carey of the tested throughempirical field studies, and even then they WashingtonState Department of Transportationfor their will be difficult to evaluate because of the challenges supportfor this project. The British ColumbiaMinistry inherentin the of study dispersal (Nathan2001). of Environment,Lands, and Parks provided us with These models a relative provide evaluation of land- most of the GIS data used for the Canadianportion of scape permeability.They highlight the most permeable our analysis area. portionsof landscapesthat could be highly disturbed.In highly alteredlandscapes, even the least-disturbedplaces may be entirely unsuitablefor animal movement. Literaturecited Users of this model must also considerthe appropriate ALMACK,J.A., W.L. GAINES, B. NANEY, P.H. MORRISON, scales for the of these application results.These analyses J.R. EBY,G.F. WOOTEN,M.C. SNYDER,S.H. FITKIN,AND were conducted using regional-scale data sets effective E.R. GARCIA.1993. North Cascadesgrizzly bear ecosystem for evaluatingbroad-scale patterns; these results should evaluation: final report. September 1993. Interagency not be expected to provide precise informationfor spe- Grizzly Bear Study Team, Missoula, Montana,USA. cific locations such as that which is requiredto identify APPs,C. 1997. Identificationof grizzly bearlinkage zones along locations for highway mitigation projects or to locate the Highway 3 corridorof southeastBritish Columbiaand southwest animalcrossing structures.These analyses are not a sub- Alberta. Aspen Wildlife Research, Calgary, Canada. stitute for field surveys. Alberta, ANDS. LOE. 1992. A This exercise is not intended to assess suitable or BEIER, P., checklist for evaluating impacts to wildlife movement critical habitat. Our corridors.Wildlife Society Bulletin modeling approach emphasized 20:434-440. resistance to animal not the evaluating movement, BJORKLAND,J. 1980. Historical and recent bear of food grizzly availability resources,denning habitats,or other sightings in the North Cascades. Miscellaneous Research features for important grizzly bears. Areas identified as Paper NCT-13. U.S. Departmentof the InteriorNational

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