Human Impacts on Bear Habitat Use Author(s): David J. Mattson 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. 33-56 Published by: International Association of Bear Research and Management Stable URL: http://www.jstor.org/stable/3872901 Accessed: 02/01/2009 16:25

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http://www.jstor.org HUMANIMPACTS ON BEARHABITAT USE1

DAVIDJ. MATTSON,Interagency Grizzly Bear Study Team, Forestry Sciences Lab,Montana State University,Bozeman, MT 59717

Abstract:Human effects on bearhabitat use aremediated through food biomasschanges, bear tolerance of humansand their impacts, and human tolerance of bears. Large- scale changes in bear food biomass have been caused by conversion of wildlandsand waterwaysto intensive humanuse, and by the introductionof exotic pathogens. Bears consume virtuallyall humanfoods that have been establishedin formerwildlands, but bear use has been limited by access. Air pollutionhas also affected bear food biomass on a small scale and is likely to have majorfuture impacts on bearhabitat through climatic warming. Majorchanges in disturbancecycles and landscape mosaics wroughtby humanshave furtheraltered temporal and spatialpulses of bearfood production.These changeshave broughtshort-term benefits in places, buthave also added long-termstresses to most bear populations. Althoughbears tend to avoid humans,they will also use exotic and native foods in close proximityto humans. Subadultmales and adult females are more often impelled to forage closer to humansbecause of their energeticpredicament and because more secure sites are often preemptedby adult males. Althoughmale bearsare typically responsiblefor most livestock predation,adult females and subadultmales are more likely to be habitu- to ated humansbecause they tend to forage closer to humans. Eliminationof human-habituatedbears predictably reduces effective carryingcapacity and is more likely to be a in factor preservingbear populations where humans are present in moderate-to-highdensities. If humansdesire to preserveviable bearpopulations, they will either have to accept increasedrisk of injuryassociated with preservinghabituated animals, or continueto crop habituatedbears while at the same time preservinglarge tracts of wildlands free from significanthuman intrusion.

Int. Conf. Bear Res. and Manage. 8:33-56

Humans(Homo sapiens) have preempteda large part informationpertaining mainly to brown (Ursus arctos) of the Earthfor their use. The attendanttransformation andAmerican black (U. americanus)bears; where appli- and depletion of ecosystems has resulted in extinction cable I also include information on polar bears (U. rates comparable to any prehistoric mass extinctions. maritimus)and Asian black bears (Selanarctos thibeta- Increasingly,humans have turnedtheir attentionto pre- nus). Humansaffect bearsmany ways. Generally,bear servingthe remainingflora andfauna. At the same time, responseto humansand their alterationsis a functionof even in cultureswhere the impetusto preservediversity food biomass changes, bear tolerance of humans and has been greatest,humans have been reluctantto sacrifice human-relatedhabitat changes, and humantolerance of their prerogativeto use lands for their exclusive benefit bears. Where and how bears use their habitat is an (Ehrenfeld 1972). Consequently, much research has integrationof these factors. I use this frameworkto been undertakento determine the level and nature of structuremy presentationof results and interpretation. human use that is compatible with retention of extant flora and fauna. This researchhas characteristicallyfit LITERATUREREVIEW into a minimalisticapproach to managingwildlife habi- tat;that is, how muchcan we do andstill retaina diversity Distributionof Bears and Humans of species sufficient to satisfy our needs? There is relatively little overlap between occupied For bears (Ursidae), this minimalistic approach is bearhabitat and high humandensities (>25/km2) (Fig. 1). evident in harvest strategies, and park and wildlands This is especially true for brown and polar bears and in management. Increasingly sophisticatedmanagement North America, although even European brown bear has entailed cumulative effects analysis (CEA) (Chris- populationsare typically centered on wildlandsand areas tensen 1986); thatis, how do bearpopulations respond to of low-to-moderatehuman densities. The Asian black the total interacting of humanactivities on a given mean- bearexhibits the greatestproportionate overlap of occu- scaled of ingfully piece ground,and does thatfit into our pied range with high densities of humans, although a managementobjectives? How bearsrespond to humans more refined distributionmap for the Asian black bear and their foods is critical input to the CEA and bear will likely show southernChinese populations restricted managementin general. The most sensitivemanagement to islands of forested higher relief terrain(cf. Servheen requires input concerning differences in bear response 1990). The Asian blackbear is notablyabsent from east- among differentsex and age classes, given thatsurvivor- centralChina, where islands of suitablehabitat are absent. and of adult ship productivity females areapparently crit- This mutuallyexclusive distributionof bearsand high ical to populationviability (Knightand Eberhardt1985, densities of humans has probablyresulted from niche Yodzis and Kolenosky 1986, Ramsayand Stirling 1988). differencesand, more importantly,from humanintoler- In this paper, I summarize and interprethow bear ance and predation. Humans inhabit extensive areas habitatuse is affected by humansand their foods. I use never occupied in recent millennia by bears. Humans have also eliminatedbears from many areas, ' including Invited paper much of temperateeastern North America (cf. Cowan Brown bear Black bear m ;c

H11 rn

Y2

oo

tz cl 0 OCCUPIED ASIAN AND AMERICAN z BLACK BEAR HABITAT OVERLAP OF OCCUPIEDBLACK BEAR HABITAT& HUMANDENSITY ) 50 z OVERLAP OF OCCUPIEDBLACK 0 BEAR HABITAT& m HUMAN DENSITY 25-50 m z

Fig. 1. Distribution and overlap of high human densities and occupied brown and black bear habitat (Banfield 1958, Bromlei 1965, Cowan 1972, Curry-Lindahl 1972, Herrero 1972, Zunino 1975, Vereschagin 1976, Yi-Ching 1981, Rand-McNally 1986, Clevenger et al. 1987, Elgmork 1987, Jakubiec and Buchalczyk 1987, Verstrael 1988). HUMANIMPACTS ON BEAR HABITAT* Mattson 35

1972, Burk 1979) andAsia (Servheen 1990), andmost of 1969a, Isakovic 1970, Pulliainen 1986, and others). In Europe(Curry-Lindahl 1972). The eliminationof grizzly the Soviet Union, drainagehas affectedca. 13 million ha bearsfrom virtually all of the westernUnited Statesin the (Ceriomuskinand Burminova1969), and has negatively absenceof high humandensities andextensive cropland, impacted brown bear populations (Sharafutdinovand between 1850 and 1930, reflects an extreme case of Kortokov 1976, Vereschagin 1976). human intolerance. Because of these exterminations, DisturbanceandRegeneration Cycles.-Humans have much bear habitatis currentlyunoccupied by bears be- contributedto the frequencyand intensityof fires under cause their progenitorswere killed by humans. primevalconditions in most ecosystems (Wilhelm 1973, Russell 1983, Christensen1988, Peet 1988);in this sense, Native Food Biomass and Habitat Structure humans have influenced bear habitat for millennia. Pathogens and HabitatConversion.-Availability of Human-causedfires were more of a factor in inherently bear foods within occupied bear habitathas been most fire-proneareas such as coastal southeastNorth America dramaticallyaffected by intentionalor accidentalelimi- and lower elevations of the Rocky Mountains,and were nationby humans. This has been effected by large-scale more common near traditionalencampments (Russell conversionof landand waterways to intensivehuman use 1983, Arno 1985, Gruell 1985). Primevalhumans gener- and by introductionof exotic pathogens. ally accentuatednatural fire cycles in a way thatreflected In the course of hydroelectricdevelopment and ma- the dependence of humans on natural habitat cycles nipulation of fisheries, humans have eliminated or re- (Russell 1983, Arno 1985, Lewis 1985). Withthe excep- duced salmonid spawners in several major drainages tion of recent centuries, wildland fire cycles, including occupied by bears, including the ColumbiaRiver head- the humanfactor, have been moreor less stablefor at least waters(Butterfield and Almack 1985, Davis et al. 1986), 4,000 to 6,000 years in forested bear habitat(Wilhelm and rivers in the northeasternUnited States (Cronon 1973, Wright1974, Arno 1985, MacDonald1987, Chris- 1983),California (Piekielek and Burton 1975), Kamchatka tensen 1988). (Lazarev 1978), and Hokkaido (Aoi 1985). This has Primeval disturbancecycles have been sometimes affecteda majorbear food in these areas,and contributed dramaticallychanged by agriculturaland technological to the decline or extinctionof bearpopulations (Lazarev humancultures. These changes have been effected by 1978, Davis et al. 1986). habitatalterations or deliberatefire control. Between 85 In North America, humans introduced2 tree patho- and 98% of virgin forests in the United States were gens thathad substantial impacts on bears. Between 1904 harvested since European settlement, largely between and 1950 virtuallyall of the previouslyabundant Ameri- 1800 and 1900 (Thomaset al. 1988). In manyparts of the can chestnuts(Castanea dentata) were eliminatedby the western and northern United States, this widespread chestnutblight (Endothiaparasitica) (Harlow et al. 1979). timber harvest resulted in unnaturalaccumulation of Chestnutswere a prolific andregular fruit producer used fuels, thatin turnprecipitated unusually widespread and by bears(Bennett et al. 1943, Harlowet al. 1979), and al- intensive fires (Whitney 1987, Peet 1988). In the north- though oaks increased after the demise of chestnuts central and northeasternUnited States, oak forests that (Callaway and Clebsch 1987, Greller 1988), loss of the replacedmost presettlementpine forests afterthese fires chestnutsprobably resulted in less productivebear habi- (cf. Dahlbergand Guettinger1956, Cronon 1983, Whit- tat. Similarly in western North America, white pine ney 1987) were probablymore productivebear habitat. blister rust (Cronartiumribicola) has virtually elimi- In recentyears, fire controlhas allowed maturationand, nated whitebarkpine (Pinus albicaulis) in wetter areas in places, senescence of forest stands initiatedby 19th- where seeds of the pine are an importantbear food (Arno century, human-causeddisturbances. Simultaneously, 1986). initiationof seres has become dependenton more regu- Conversion of bear habitat to intensive agriculture, lated smaller-scaletimber harvest. industry,and human habitation has been andcontinues to In southeastNorth America, European settlers tended be widespread,with negative impacts on bear popula- to perpetuateIndian fire managementpractices. Fre- tions;as in California(Lawrence 1979) andEstonia (Kaal quent fires enhancedforage quality, fruit productionof 1976). Loss of importantforaging and refuge areasdue trees, and efficiencies of acorn and chestnut collection to and drainage developmentof wetlandsis an especially (Wilhelm 1973, Christensen1988). These low-intensity critical issue in both the United States (Hugie 1979, fires also maintainedpine forests at the expense of oaks Hamilton and Marchinton 1980, Manville 1983, and (Waggoner 1975, Callaway and Clebsch 1987, Chris- others) and Europe (Stroganov 1962, Novikov et al. tensen 1988) and were probably detrimentalto bears 36 BEARS-THEIR BIOLOGY AND MANAGEMENT especially on the coastal plains (cf. Maehr and Brady incentivefor more intensivemanagement exists. This is 1984). Since effective fire control began in the early especially true of Pacific coastal North America, al- 1900's, many pine forests have succeeded to oak (Wag- thoughmore intensive silvicultureis being increasingly goner 1975, Christensen1988). At the same time, exten- practicedelsewhere. Very little bearfood exists in young sive pine plantationshave been established and main- closed-canopyforests in wet Pacific coastal regions (A. tained by prescribedfire (Dixon 1965). Hamilton 1987, pers. commun.). Most shrubsin these Vegetation succession on abandoned cropland is regions are susceptible to herbicidecontrol (Gratowski anotherfactor introducedby humans in the landscape 1978, Lawrence 1979), and even shrubs that resprout dynamicsof easternNorth America. Croplandabandon- after herbicide treatmenttend to be less vigorous and ment increased since 1900, and typically resulted in producesubstantially less fruit(Stewart 1974, Gratowski highly productive bear habitat during early and mid- 1978). The same is true of shrubsimportant to bears in successional stages of recovery (cf. Alt 1980b, Keever eastern deciduous and mixed-conifer regions of North 1983, Pelton 1987, Greller 1988). America (cf. Gill and Healy 1974, Hall and Nickerson Western and boreal Canadais in the early stages of 1986, Rogers 1987), and in boreal regions (cf. Hall and widespreadtimber harvest (cf. Horejsi 1986) and effec- Shay 1981). tive fire control. In most of Canadaas well as in wetter Ultimately,the effects of timberharvest practices on or higherelevation regions of the westernUnited States, bear food biomass in any given area depend on the 40 to 60 years of effective fire control by humanshave autecology of individual bear foods. In areas where probablynot haddramatic impacts on vegetationdynam- arborealspecies contributesubstantial amounts of food, ics andmosaics, given 100- to 500-yearnatural fire cycles managementfavoring forest developmentis beneficial. in most of these regions (Romme 1982, Foster 1985, However, for stone pines (Pinus, subsection Cembrae), Dymess et al. 1986, Franklin1988). the potentialbenefits of timberharvest are very limited Assessing the impacts of human-causedchanges in given the 100 yearsor more generallyrequired for stands disturbancecycles depends on our understandingthe to start producing significant seed biomass, and the comparabilityof timber harvest and wildfire effects. subsequentlong-term productivity of a stone pine forest Severalgeneralizations can be madeabout timber harvest (Iroshnikov 1963, Kozhevnikov 1963, Arno and Hoff effects on productionof bear foods. Most post-harvest 1989). However, in most regions productivityof bear site scarificationor harvest on dry or exposed sites is habitatis keyed to the first 100 years of succession (cf. detrimental.Scarification eliminates most berry-produc- Fowells 1965,Dyrness 1973, Gill and Healy 1974,Lindzey re- ing shrubsfor severaldecades (Minoreet al. 1979, Zager et al. 1986, Greller 1988, and others), and reflects 1980, Martin 1983), and overstoryremoval on dry sites sponses by fire-adapted,fruit-producing species (Wright removes the protective canopy that would otherwise 1972). Again, wet Pacificcoastal areas pose anexception et al. persist with typically frequent and low intensity wild- to this generalpattern (Alaback 1984, Lindzey 1986, fires. Timberharvest followed by no post-harvesttreat- Hamilton 1987) (Fig. 2). of ment or by broadcast burning produces the greatest Timber harvest also affects availability denning amountsof bearsfoods, especially on moist-to-wetsites trees. Large-diameterhollow trees are preferentially Americanblack bearsin (Minoreet al. 1979, Zager 1980, Bratkovich1986, Hillis used for den-sites by Asian and and Cowan 1986, and others). Early successional communitiesfol- temperate regions (Bromlei 1965, Jonkel and Meslow Hamiltonand March- lowing these silviculturalpractices are most similar to 1971, Lindzey 1976, Wathenet al. and Retention those precipitatedby wildfire (Martin1983, Zageret al. inton 1980, 1986, others). trees is not 1983). Thinning also tends to enhance bear habitat and productionof these denning compatible with the 70- to timberrotation in most productivity,and again more so on wettersites (cf. Pelton 150-year practiced Loss of 1979, Alaback 1984, Uress 1985, Young and Beecham temperatecommercial forests (cf. Burns 1983). den-sitetrees is not 1986); fruit productionby trees typically increaseswith large-diameter,old-growth probably but at the same time stress, black bear thinning(Wilhelm 1973, Pelton 1979). critical to, may Most benefits associated with timber harvest are populations(Lindzey and Meslow 1976). most the mosaic differsbetween a by intensivemanagement designed to accelerate In areas, vegetation negated harvest crownclosure andeliminate competing vegetation. This natural fire and a fire control/timber regime. settlersand tendedto usually involves scarification,planting, and control of Historically,European developers over a area. As shrubs and herbs, and is more common in the most reducediversity of vegetationseres large a the size of increased and productivetimber producing areas where the economic result, vegetation patches HUMAN IMPACTS ON BEAR HABITAT * Mattson 37

TEMPERATE COASTAL TEMPERATE DECIDUOUS timber harvest (Azuma and Torii 1980, 1.o - widespread FRUITS CAMIBIUM \..TREE timber \-REE Furubayashiet al. 1980). Bears use commercial to areas clearcut and in r \SHRUB \ stands adjacent being generally I FRUITS\ I harvest and manmade stands are I areas where timber I ' I o 0- I I extensive. Bear use of cambiumon Honshu is m probably o o relatednot only to landscapedynamics of food biomass, o BOREAL ROCKY MOUFNTAIN - but also to avoidance of areas without cover recent oSHRUB - (i.e., ILS\ , oS , IzRUIT / P-' i. clearcuts). 0.50- - Black bearswill also very likely sufferfrom continued habitat in western and Wash- A major degradation Oregon 0- L O 50ss 100 Y50 200 300 T 0 A ington. Within the next 50 years, unproductivemid- YEARS SINCE DISTURBANCE successional stages will increase from ca. 20 to 65% of the total forested due to historical Fig. 2. Relative bear food production under primeval conditions in different landscape widespread vegetation strata for 4 majorecosystems. Productionis scaled from0-1, and is and contemporaryold-growth clearcutting (Harris et al. relativeto each stratum and ecosystem. These graphs synthesize a review of This shift will stress bear literaturethat pertains to vegetation succession in each of these ecosystems. 1982). undoubtedly popula- References can be obtained from the author. tions, even given continuedpropagation of early succes- sional shrubfields. In addition, shrubcontrol is widely probably rendered temperate bear populations more practicedon commercialforest lands in western Oregon vulnerableto successional change. On the other hand, and Washington (cf. Dimock et al. 1976) and berry abandonedfields reintroduceda smaller scale mosaic. productionon new seres will often not be realized. Recent silvicultural practices also emphasize smaller Pollutantsand Toxins.-Bear food biomass andhabi- harvestunits and "sustainedyield" of wood products(cf. tat structurehave been, and will continue to be, affected Bums 1983). This has resultedin an unstablevegetation by atmosphericpollutants. Increased atmosphericcar- mosaic of diverse-agedsuccessional communities (Fran- bon dioxide andtrace gases, "smog",and acid deposition klin and Forman 1987). The more recent tendency to have alreadyaltered or promiseto alterbear habitat. The generate smaller scale mosaics is also constrained by effects of acid precipitation(pH < 5.6) on overall vegeta- existing forest structure. tion structureand productivityhave not yet been conclu- Forest managementpractices have almost certainly sively documented (Smith 1981), although decline of contributedto epidemic bear use of tree cambium in spruce (Picea spp.) in western Europeand the northeas- commercialforests. In coastal Washingtonstate, wide- tern United States has been almost certainlytied to acid spread timber harvest at low elevations during the late deposition(Tomlinson 1983). On the otherhand, signifi- 1800's and early 1900's produced a disproportionately cant air pollution impacts on vegetation have been con- large area of productive shrub fields, and local bear clusively documented(Smith 1981), but are restrictedto populationsconsequently increased (Poelker and Hartwell limitedareas downwind of smeltersand major metropoli- 1973, Lindzey et al. 1986). In most instancesthese shrub tan areas. Generally, vegetation diversity decreases fields were succeeded without replacementby closed- (Guderianand Kueppers 1980, Chubanov 1986) along canopy, pole-size forest. Local bear populations were with abundance of many fruit-producingspecies (cf. likely under nutritionalstress and probablyreverted to VanderKloet andHall 1981, Chubanov1986). Although use of secondary or successionally abundantfoods, in- abundanceof fruit-producingspecies may increase in cludingtree cambium. In wet coastal areas,tree diameter some situations(cf. Kickertand Gemmill 1980, Shugart andage classes used most heavily by bearssucceeded and et al. 1980), fruit production of both shrubs and trees replaced productive shrub fields (Fig. 2) (Fritz 1951, typically declines due to leaf damageand stresses associ- Glover 1955, Poelker and Hartwell 1973). This may ated with decreasedphotosynthetic efficiency (Cowling explain the otherwiseunexplained epidemic use of cam- andDachinger 1980, Scale 1980, and others). Typically, bium in certain coastal locales. Poelker and Hartwell high levels of air pollution negatively affect bear food (1973) speculatedthat cambium use in westernWashing- biomass, but over a small portion of occupied bear ton was related to the lack of Rubus spectabilis in bear habitat. diets. R. spectabilis is abundantalmost solely in open, Increasedatmospheric CO2 and trace gas concentra- typically newly clearcut areas (Franklin and Dyress tions will likely increasethe Earth'stemperature 1 to 5 C 1969, Smith 1978, Alaback 1984). In Honshu, Japan, by the end of this century (Dickenson and Cicerone Asian black bear use of tree cambium is also related to 1986). Temperatureincreases will be greatestat mid- to 38 BEARS-THEIR BIOLOGY AND MANAGEMENT high latitudes (Dickenson and Cicerone 1986), in the carnivoressurvived. rangeofmost occupiedbear habitat. By the 22ndcentury, Typically, bear populations are benefited by high averagetemperatures may be higher than any in the last ungulatedensities, whereashuman hunting of ungulates 10 million years (Dickenson and Cicerone 1986, Kerr can be both a benefit and detrimentto bears. Density, 1986). In response to this change, vegetation zones productivity,and distributionof bears have been posi- would shift north, and shrink or expand. In Canada, tively relatedto ungulatedensities (Kaal 1976, Mattson greatestincreases are projectedfor grassland,cool tem- et al. 1987, Reynolds and Garer 1987). However,even perate forest, and maritime boreal forest, and greatest at moderateor high densities, a human-harvestedungu- decreases for dry and moist continental boreal forest latepopulation is likely to be less productivefor bears.On (Rizzo 1988, Zoltai 1988). Because grasslands and the average, hunted ungulate populationsare healthier maritime boreal forest (Payne 1978) are typically not and more vigorous, and significantly below ecological productive bear habitat, and cool temperate forest is carryingcapacity comparedto an unhuntedpopulation likely to increasein the rangeof blackbears, grizzly bears (Connolly 1981, Mohler and Toweill 1982). Conse- would likely sufferfrom these predictedchanges in North quently, fewer winter-killedand weakened animals are American vegetation. The increasing number of con- available to bears during the spring. With harvest that fined and isolated bear populations would also be at usuallyemphasizes bulls, fewer adultmale ungulatesare greater risk with shifts in vegetation zones, given the also critically weakened by the rut and so vulnerableto static boundariesof their circumscribedrange. bear predation. On the other hand, ungulateharvest by Othermiscellaneous pollutants and toxins pose risks humanscan benefitbears primarily by generatingcarcass to bears. Polarbears could be greatlyaffected by ocean- remains and wounded animals (Haglund 1968, 1974; borneoil spills as a resultof thermoregulatoryand meta- Servheenet al. 1986). bolic stresses from toxicity of crude oil ingested during grooming(Anonymous 1981). Polarbears could also be Human Foods indirectlyaffected by seal populationdeclines. The risk AgriculturalCrops.-Bears make substantialuse of of oil spills to any given polarbear population would be agriculturalcrops wherever they are available. Bears a functionof the prevailingocean currentdirection (Stir- principally use apiaries and cereal, fruit, and forage ling et al. 1980, Stirlingand Kiliaan 1980). Historically, crops. Among cereal crops, bears make greatestuse of strychninepoisoning killed a large number of grizzly oats (Avenasativa) andcorn (Zea mays). Bearuse of corn bears in North America, whether by the intention of was mentioned in 11 and oats in 14 research articles humans or not (Storer and Trevis 1955, Brown 1985). (Fig. 3). Bears make less frequentor incidental use of However, contemporaryuse of strychnine to control barley (Hordeum vulgare) and wheat (Triticum aes- rodentpopulations in the Yellowstone areahas not been tivum). Peak use of oats and corn begins at the "milk" considereda threatto bears (Bares et al. 1980). stage andcontinues until harvest, usually August through UngulatePopulations.-Bear populationshave likely Septemberfor oats (Spencer 1955, Novikov et al. 1969b, been influenced by human management of ungulate Kaletskayaand Filinov 1986, Cicnjaket al. 1987), and Aoi populations(Peek et al. 1987). Ungulates are a poten- fall (Davenport1953, Alt et al. 1977, 1985, Garer for tially importantand high value diet item (Mealey 1980, and Vaughan 1987) into winter(Landers et al. 1979) Bunnelland Hamilton 1983), andbears preferentially use corn. Least corn use occurs in July in eastern North meat where it is available. This meat is often from America,as a resultof preferencefor native fruitsat that et al. Oats scavenging on ungulate carcasses, but bears are also time of year (Alt et al. 1977, Landers 1979). in known to kill ungulates outright (Filinov 1980, Cole grow more commonly in areas with cool, and corn 1972, Semenov-Tian-Shanskii1972, and others). areas with hot, growing seasons (Stoskopf 1985); bear Use of corn Ungulatepopulations have been dramaticallyaffected use coincides with this distribution(Fig. 3). common than use of oats in areas by humans,beginning perhaps as long ago as the Pleisto- appearsto be more a of cene (Martin1984). The extent, local densities, and sex whereboth crops occur andis probably consequence concentration Subcom- andage classes of populationshave all been manipulated. corn's greaterusable energy (cf. Nutrition Generally,populations of large ungulateshave not been mittee on Swine 1979, Stoskopf 1985). not bearuse of compatible with intensive agricultureand high human Usable energydoes explaininfrequent densities (Reed 1981, Bryant and Maser 1982). But wheat,the most widespreadof northernhemisphere grain for wheat is to ungulateshave fared better than bears and wolves, and crops. Metabolizableenergy comparable instancesof wheatuse bearsare rarely have large ungulates been eliminated and these corn,and yet recorded by HUMAN IMPACTS ON BEAR HABITAT * Mattson 39

QU11

O BEAR USE OF OATS A BEAR USE OF CORN T BEAR USE OF CAMBIUM m OCCUPIED BEAR HABITAT [l OATS CROPLAND CROPLAND 3 CORN CROPLAND DH OVERLAP * OATS & CORNCROPLAND OF CROPLAND AND OCCUPIEDBEAR HABITAT

Fig. 3. Main distribution of oats and corn crops, and recorded instances of corn Fig. 4. Distribution and overlap of cropland and occupied bear habitat (Reader's and oats use by bears (Ceriomusckin and Burminova 1969, C.I.A. 1974). Re- Digest Assoc. 1985). corded instances of "epidemic" cambium use are also mapped. rare. The difference may be due to characteristicsand croplands.Grain crops are undoubtedly high qualitybear distribution of wheat and oat fields. There is not a food; crude protein content ranges from 9 to 13% and substantialdifference in overlap between bear distribu- starchcontent from 54 to 73% for majornorthern hemi- tion andmajor oat and wheat cultivation. However, oats sphere grain crops (Subcommitteeon Swine Nutrition are more commonly cultivatedin small forest fields and 1979). However, bear use of this high quality food in wheatin areasof extensive contiguouscropland (Symons most bear habitatis prohibitedby humanintolerance. 1972). Most bear use of oats and corn occurs in isolated Bearuse of domesticatedfruits, primarily apples (Malus forest fields or close to cover in more extensive cropland domestica)and secondarily plums and pears (Prunus spp. (Ognev 1931; Davenport1953; Spencer 1955; Novikov andPyrus communis),is also widespread.Domesticated et al. 1969a,b;Landers et al. 1979;Klenner 1987). Wheat fruitsare known to be a majorpotential part of beardiets may be less availableto bears because there is typically in western Montana(Servheen 1983), ShenandoahNa- unfavorablejuxtaposition of wheat fields and cover. tional Park(Garer and Vaughan 1987), and Pennsylva- Domesticatedgrains are potentially significant to bears. nia (Bennett et al. 1943). Use generally peaks July Oats are especially importantto some Europeanbrown through October, after the fruit crop ripens (Spencer bearpopulations (cf. Kaal 1976, Cicnjaket al. 1987), and 1955, Servheen 1983, Cicnjak et al. 1987, Garer and the availabilityof oats apparentlyinfluences bear density Vaughan1987). Bears typically make greatestand most (Novikov et al. 1969a) and movements (Kaletskayaand consistent use of "wild" trees and abandonedorchards Filinov 1986). Cornis of apparentlyequal importanceto (Bennettet al. 1943, Spencer 1955, Zunino and Herrero some easternNorth American black bear populations (cf. 1972, Manville 1983, Garer andVaughan 1987). Use of Landerset al. 1979). maintained orchards more often occurs during years Bear use of grain crops is primarilyrestricted by the when native bear foods are in short supply (Slobodyan absence of bears from most intensively cultivatedareas 1976, Novick and Stewart 1982). Most use (Fig. 4). crop occursat the interfaceof wild- and Bears have used apiariesfor centuries,wherever they 40 BEARS-THEIR BIOLOGY AND MANAGEMENT are accessible. Jorgensenet al. (1978) reviewed bearuse native foods are scarce (Eide 1965, Brown 1985). As of apiaries, in the context of human-bear conflicts. with sheep, predationon cattle appearsto be greaterin Generally,timing of bear use varies among regions, but more remote areas with greatercover (Novikov 1956, is consistent with peak honey production. Novikov et al. 1969a, Bjorge 1983). Bears often use Introducedforage, principallylegume crops, receive carrion from cattle that have been poisoned by native substantialuse by some bearpopulations, as in the Swan toxins (Jorgensenet al. 1978, Brown 1985, Greer 1987). Hills of Alberta(Nagy and Russell 1978), northwestern Much of this scavenging has been falsely interpretedas Montana (Jonkel and Cowan 1971), and Yellowstone predation(Knight and Judd 1983, Brown 1985). National Park (Graham 1978). Mixes of introduced Morethan predation on sheep,bear predation on cattle legumes and grasses are especially significant during appearsto vary with availability of high quality native years when native fruits or seeds are in short supply. foods. In the Soviet Union, cattle and horse predation Domestic Animals.-Bears use most domesticated consistently increases during the summer and fall of animals common to the northern hemisphere (sheep years when high quality native foods are scarce (Ognev [Ovisaires], cattle [Bos taurus],swine, horses [Equusca- 1931, Bromlei 1965, Ustinov 1965, Shartafutdinovand ballus], and goats [Capra bircus]). Significantbear use Korotkov 1976, and others). Similarly,LeCount (1980) of sheep has been recorded in western North America attributedlack of conflict between black bears and live- (Jorgensenet al. 1978, Johnson and Griffel 1982, Jor- stock in centralArizona to high quality bear habitat. gensen 1983, Brown 1985), and for isolated European Bearsexhibit distinct preferences for differentspecies bear populations in Spain (Clevenger et al. 1987), the and age classes of domestic livestock. The order of Pyrenees(Faliu et al. 1980, Roben 1980, Berducouet al. preferencefrom greatestto least is roughly:swine, ewes, 1983, Camarra 1986), Italy (Krott 1962, Zunino and lambs,calves andyearling cattle, cows, horses,and bulls. Herrero 1972, Zunino 1981), and Norway (Mysterud Several authorshave observed that bears prefer swine 1973, 1976, 1980a). Moreincidental use of sheep occurs over all other livestock (Storerand Trevis 1955, Brown elsewhere. Bear predationon sheep in all of these areas 1985) or that swine are disproportionatelypreyed upon occursprimarily from July or Augustthrough September, by bears (Brown 1960, Slobodyan 1976, Horstmanand coincident with the tenure of sheep on summer range. Gunson 1982). Aside from this apparentpreference, While on summerrange, sheep are in closer contactwith vulnerabilityof domesticlivestock is likely a functionof bearsand are less closely attendedthan any othertime of size-mediatedbear preference, local beardensity, cover, year (Mysterud 1973, Horstman and Gunson 1982, and how closely the animals are attended. Bulls appear Johnson and Griffel 1982, Jorgensen 1983, Camarra to be nearly invulnerableto predation;sheep are killed 1986). In Alberta,Horstman and Gunson (1982) specu- more consistentlyand at higherrates thancattle (Brown lated that greaterproportionate bear predationon sheep 1960, Horstman and Gunson 1982, Knight and Judd comparedto cattle was largely a result of sheep being 1983, and others), and calves and yearlings more often stocked in more remote areas. In the Pyrenees, sheep thanany otherclass of cattle (Murie 1948, Bjorge 1983, comprise a significant part of the overall summerbear Knight and Judd 1983). diet (Faliuet al. 1980, Berducouet al. 1983), andin other Domestic livestock has additional, typically detri- areas,a significantpart of individualbear diets (Mysterud mental,effects on bears. Livestockgrazing has modified 1980a,b;Jorgensen 1983). Bears tend to more often kill vegetationcomposition and structurein many areas. In ewes than lambs (Brown 1960, Mysterud 1973, Horst- California,the Rocky Mountainsof Montana,and the man and Gunson 1982) and occasionally engage in mass CantabrianMountains of Spain, livestock browsinghas killing of sheep (Mysterud1976, Jorgensenet al. 1978). reducedor eliminatedrecruitment of desirabletree spe- Significantuse of cattlehas been notedthroughout the cies. Oaks have been most affected in Californiaand Soviet Union and in westernNorth America, more often Spain (Rossi 1980, Clevenger et al. 1987, Reed and by brownbears than black bears. For a briefperiod in the Sugihara 1987) and aspen most affected in Montana western United States, cattle constituted an important (Aune 1985, Stivers 1988). Some studiesindicate that in bear food and may have contributedto bear population the absenceof fire, livestockgrazing reduces competition increases (Bailey 1931, Storerand Trevis 1955, Brown with maturemast-producing oaks in California(Duncan 1985). Timing of bear predationon cattle varies more et al. 1987, McClaran1987), but grazingprobably does thanfor predationon sheep, but generallycoincides with not mimic fire effects in long-termoak standdynamics. for dispersalof cattleon summerranges (Murie 1948, Knight Reductionof forest cover by livestock or by humans andJudd 1983), or with springand fall when high quality livestock generallymakes habitatless secure,especially HUMAN IMPACTS ON BEAR HABITAT * Mattson 41

for European brown bear populations (Krott 1962, of humanfoods among species, individuals,and sex and Camarra1983, Clevenger et al. 1987). age classes, dependingon the food, season,and proximity Effects of livestock grazing on ground layer bear to humans. foods are more ambiguous and largely a function of Generally,larger bears prey on largeranimals. Adult timing, location, and intensity. In Montanaand Wyo- malesprey most often on cattle(Eide 1965, Horstmanand ming, unregulatedearly season grazingin riparianzones Gunson1982, Knight and Judd 1983, data from Craighead or avalanchechutes is detrimental(Mealey et al. 1977, et al. 1988) and are also the typical predatorson sheep Irwinand Hammond1985, Stivers 1988). Sheep brows- (Davenport 1953, Mysterud 1980a). Subadults more ing also reducescover andproductivity of most important commonly prey on smaller animals such as sheep and fruit-bearingshrubs (cf. Sharrowet al. 1989). Although yearlingcattle (Mysterud1980a, Knightand Judd 1983), heavy grazing on mountain meadows tends to reduce and females are consistently underrepresentedas preda- overall vegetation biomass (Leege et al. 1981, Ratliff tors on domestic livestock. 1985, Ignat'eva 1987), plant species preferredby bears Few data are available that concern differences in (such as, dandelion[Taraxacum spp.], clover [Trifolium bear-classuse of agriculturalcrops. However, the few spp.], timothy [Phleum alpinum], and bluegrass [Poa observations suggest 2 hypotheses: (1) adult females spp.]) tend to increase in abundance (Bonham 1972, more commonly use crops within establishedranges (cf. Leege et al. 1981, Ignat'eva 1987). Brown (1985) sug- Alt et al. 1977, Garner and Vaughan 1987), and gested that widespread "overgrazing"resulting from (2) subadultmales more often use crops (and dumps)on introductionof cattlein Arizonaand New Mexico caused the peripheryof occupiedbear habitat (cf. Gunson 1975, the loss of many bear foods either from direct use or al- Gunson and Cole 1977, Young and Ruff 1982, Klenner terationof hydrologicregimes, andreduced productivity 1987). of riparianzones. With more conservativemodem-day In many study areas, males are disproportionately public landmanagement, livestock grazingprobably has representedamong bears visiting human facilities or little direct impacton bearfood biomass (Stivers 1988). involvedin depredations.In some areasrepresentation of Edible Human Refuse.-Not much needs to be said males has been in the rangeof ca. 60-65%(Alt et al. 1977, about human garbage as a bear food. Bears have used Claaret al. 1986, Mace et al. 1987, datafrom Craighead edible garbagevirtually everywhere it is available. Ed- et al. 1988). This disproportionalitycan easily be attrib- ible was an garbage importantfood for bearpopulations uted to the greater probabilityof males encountering in Canada Newfoundland, (Payne 1978) and Yellow- pointor linearfeatures as a resultof typicallylarger range stone National Park (Bames and Bray 1967, Craighead sizes (Rogers et al. 1976; Bunnell and Tait 1981, 1985) and Craighead1971), and servedas an attractantin many and the seasonal exclusivity of adultfemales associated other areas. and Meagher Hape (1987, Yellowstone with core use areasin some regions:Alberta (Young and National Park estimated that files) 4,800 tons of edible Ruff 1982, Pelchat and Ruff 1986), Minnesota(Rogers were garbage availableeach yearfrom open-pit dumps in 1987), arctic regions (Nagy et al. 1983a,b), and central Yellowstone Park during the mid-1960's. Edible gar- Colorado (Haroldson, in prep.). However, the >70% is a food that bage high quality has been shown to explain male compositionof bearsvisiting dumpsor otherhuman differencesin and weights productivityamong individual facilities in Minnesota(Rogers 1987),northern Michigan bears and in populations Michigan(Rogers et al. 1976), (Rogers et al. 1976), northernCalifornia (Piekielek and Minnesota andYellowstone Park (Rogers 1987), (String- Burton1975), New York(Black 1958), andGreat Smoky ham Blanchard In 1986, 1987). national parks, where Mountains National Park (Beeman and Pelton 1976, human is concentrated the activity during summermonths, Singer and Bratton1980) defies such an explanation. In use of and humanfoods peak garbage occurs from June these areassome otherfactor, most likely active selection or July and throughAugust (Craighead Craighead1971, on the partof males, explains the disproportionality. Harms and Pelton 1980, Eagle 1983). In other areas, A positive relationship is apparentbetween domi- use garbage occurs during spring and fall, when high nanceof a bearclass andfavorable attributes of sites used native quality foods areless abundant(Hatler 1972, Alt et to forage on human foods. Adult males tend to use al. 1977, and Ruff et al. Young 1982, Nagy 1983a). typicallylarger dumps farther removed from humans (Alt et al. 1977, Tietje and Ruff 1983, Rogers 1987). In Bear Behavior Newfoundland and in Yellowstone Park before 1970, Use Foods.-All bearsdo not ofHuman benefitequally both sexes of adults either had prerogative on edible fromhuman foods. Thereis considerable variationin use garbage (Hornocker1962) or were nearly sole users of 42 BEARS-THEIR BIOLOGY AND MANAGEMENT

largerdumps (Payne 1978). No black bears other than use of humanfoods in the backcountry. In the Yellow- large males typically used dumps in Yellowstone in the stone area,adult females constitutea disproportionately face of competition from grizzlies (Barnes and Bray large part of bears scavenging from outfitter camps 1967,Craighead and Craighead 1971). Inboth Newfound- (Hoaket al. 1983, datafrom Craighead et al. 1988). In the landand Yellowstone Park, edible garbagewas an impor- Great Smoky Mountains, "troublesome"backcountry tantfood for the populationwhereas in otherstudy areas, bears are mostly adultmales (Beeman and Pelton 1976, where dump use was mostly by adult males (Alt et al. Singer and Bratton1980). The situationin Yellowstone 1977, Tietjeand Ruff 1983, Rogers 1987), edible garbage does not contradictthe hypothesisthat more subordinate was apparentlya supplementalfood importantto only a or security-conscious bears are more likely to forage few bears. The greateruse of dumps by subadultmales nearerto humans. Singer and Bratton(1980) hypothe- in east-centralAlberta (Young andRuff 1982) andnorth- sized that high levels of adult male involvement at ern Michigan (Rogers et al. 1976) may be explained by backcountrycampsites in the Smokies were attributable removalof adultmales neardumps as a resultof selective to locationof campsitesin high qualitybear habitat, along hunterharvest of trophies or less wary bears. Among naturaltravel routes. polarbears near Churchill, Manitoba, family groupsand Two other behavioralphenomena characterize bear subadultswere the principalusers of the dump, likely use of human foods. Use is typically nocturnal and because adultmales were disinterestedin edible garbage usually increases when high quality native foods are in duringthe periodof onshoreinactivity (Lunn and Stirling shortsupply. Bearuse of oats in the Soviet Union (Ognev 1985). 1931, Novikov et al. 1969a) andcorn in the UnitedStates Adultfemales andsubadults tend to occupy areasnear (Davenport1953, Brown 1985) typicallyoccurs at night; humansmore than adult males; as along spawningstreams as does use of campgroundsand areasnear human facili- on AdmiraltyIsland (Warer 1987), near developments ties (Barnesand Bray 1967, Harms1980, Schleyer 1983, in Yellowstone NationalPark (Mattson et al. 1987), and Tietjeand Ruff 1983, Harting1985, Ayreset al. 1986,and along roads in the FlatheadValley of British Columbia others) and predationon confined domestic livestock (McLellan and Shackleton 1988a) and Denali National (Davenport 1953, Zunino and Herrero 1972). During Park,Alaska (Tracy 1977). Nearly all panhandlerblack years of poor native food production,increased bear use bearsin Yellowstone Parkand a disproportionatelylarge of agriculturalcrops and humanfoods, and predationon numberin the GreatSmokies were adultfemales (Barnes livestock have been recordedfor California(Piekielek and Bray 1967, Tate and Pelton 1983). Subadultmales and Burton 1975, Novick and Stewart 1982), the eastern also compriseda largeportion of bearsforaging at camp- United States (Spencer 1955, Elowe 1984), contempo- groundsin Yellowstone Park,expecially before 1970 (cf. rary Yellowstone National Park (Knight et al. 1988), Craigheadet al. 1988), and at small dumps near human borealCanada (Young and Ruff 1982), the Soviet Union facilities in Alberta(Tietje and Ruff 1983). On the other (Bergman1936, Bromlei 1965, Ustinov 1965, Slobodyan hand, females with cubs-of-the-year tended to avoid 1976, and others), and the Alps (Krott 1962). These 2 developmentsin Yellowstone Park(Mattson et al. 1987), phenomena, as well as the propensity to use cropland trails in Glacier National Park,U.S.A. (McArthur-Jope isolatedor close to cover, suggest thatmost bearstend to 1983, Jope 1985), anddumps in Alaska (Dau 1989). The minimize contact with humanseven while using human closeness of humansmay providesubadults and females foods. Wherereliance on humanfoods is greatest and with young refuge and an opportunityto use higher competitionfrom otherbears significant, bears are more quality foods otherwise preemptedby dominant adult likely to expose themselves to humansin the process of males (Tietjeand Ruff 1983, Mattsonet al. 1987, McLel- getting human foods (e.g., Yellowstone National Park lan andShackleton 1988a). Whethera female with cubs- [Barnesand Bray 1967, Craigheadand Craighead1971] of-the-year uses the areas close to humans probably and Jasper[Herrero 1983]). Facilities.- depends on the quality of food at stake and her level of Response to HumanRecreationists and habituation. The tendency for especially adult females Bearsgenerally avoid humanstraveling in the backcoun- and subadultmales to range closer to humans may ex- try,although sometimes bears apparently preferred to use and In plainthe greaternumber of habituatedbears among these human-maintainedtrails (Garner Vaughan1987). classes observedin Yellowstone Parkand Alaska (Tracy the Cabinet Mountains of Montana, bears used areas 1977, Mattson et al. 1987, Warner 1987, Olsen et al. within 100m of trailsless thanexpected especially during 1989). hunting season (Kasworm and Manley 1990). With Few studies have recordeddifferences in bear-class increased levels of trail use by humans in Glacier Na- HUMANIMPACTS ON BEAR HABITAT* Mattson 43 tional Park, Montana,habituated bears remainingnear roads less than expected year-round;greater than ex- trailsexhibited a weakerresponse to humans(McArthur- pected use of fire roadsby females was attributedto use Jope 1983, Jope 1985). Bears tended to flee humans of native fruitsgrowing in the roadclearing (Garnerand when encounteredin open backcountryareas (Chester Vaughan1987). In westernNorth Carolina, frequency of 1980, Haroldsonand Mattson 1985, McLellan and Shack- road crossings by bears is negatively related to road leton 1989, Gunther 1990), although when bedded in traffic (Brody and Pelton 1989). otherwise secure areas bears were inclined to either not Bears generally exhibit the strongest avoidance of move or to attack (Schleyer et al. 1984, Haroldsonand occupiedfront-country human facilities. In Yellowstone Mattson 1985, McLellan and Shackleton 1989). There Park,spring bear use of ungulatecarcasses is ca. 90%less was also a negative relationship between number of and summerbear use of spawning cutthroattrout (On- people and number of bears observed in nonforested corhynchusclarki) 30-90% less than expected near rec- portionsof PelicanValley in Yellowstone Park(Gunther reationaldevelopments (Mattson and Henry 1987, Rein- 1990). The response of grizzly bears to infrequentoff- hart and Mattson 1990). The effect on carcass use trail encounters with people in the backcountry was extendsout 5 km (Mattsonand Henry 1987). Otherwise, short-lived and not energeticallycostly in Yellowstone bears tend to avoid Yellowstone Park developments Park(Haroldson and Mattson1985) but more extremein during daylight hours out to 5 km during summer and the nonparkFlathead area of BritishColumbia (McLellan 3 km duringfall, and have theirdaylight foraging activi- and Shackleton 1989). In Europe,off-trail or backcoun- ties disruptedout to 3 km duringspring and summerand try recreationalactivities such as mushroomand berry 4 km duringfall (Mattsonet al. 1987). Habituatedbears pickingwere apparentlyvery intrusiveto bears(Novikov account for most use within 3 km of developments et al. 1969a, Kaal 1976, Buchalczyk 1980, Zunino 1981, (Mattson et al. 1987). In Norway, Mysterud (1983) Roth 1983). observed that bears never bedded within 0.55 km of Bear response to people residing at backcountry inhabitedfarms and Elgmork (1978, 1983) observedthat campsitesis usuallystronger than their response to people bearuse of areaswithin 2 km of cabins declined substan- on trails. Bears tend to underuseareas within 0.8 to 1.0 tially as numberof cabins increased. The decline in use km of campsites(Gunther 1990; Mattson, in prep.)and to of habitat near cabins was not explainable by hunting have theiractivities disrupted up to 2.5 km away (Zunino pressure (Elgmork 1978), and bear use of areas near 1981;Mattson, in prep.). These effects were evidentonly abandonedfarms was common (Mysterud1983). for the most heavily used campsites(>40 people/month) Europeanbrown bears are vulnerableto humanintru- (Mattson,in prep.)or campsitesnear open areas(Gunther sion and requirehabitat secure from human use (Krott 1990) in Yellowstone National Park. and Krott 1963, Elgmork 1978, Buchalczyk 1980, Zun- Anglers also affect bear habitatuse in the backcoun- ino 1981, Camarra1983, Roth 1983, Clevenger et al. try; a negative relationshipexisted between numberof 1987, andothers). Apparently,traditional partitioning of anglersand bearfishing activity on spawningstreams in habitatby Europeanbrown bears and ruralhuman resi- Katmai National Park, Alaska (Olsen et al. 1989) and dents has facilitated mutual avoidance (Zunino 1981, Yellowstone Park (Gunther 1984). Olsen et al. (1989) Roth 1983, Clevenger et al. 1987). Certain,sometimes also observedthat during peak angleruse, bearsavoided small, areas were rarely visited by humans and consti- anglersby shiftingtheir fishing activityto evening hours tuted extremely importantrefuges for bears. With the when angler use was lowest. adventof moder recreationists,the traditional"balance" McLellan(1990) has reviewedthe effects of industrial has apparentlybroken down andformerly secure sites are roadsand activities on bears;bears generally avoid open no longer so (Zunino and Herrero 1972, Zunino 1981, industrialroads. Bears also avoid daytime traffic on Roth 1983). The existence of specific sites secure from commercialand recreationalroads, by as much as 500 m humanintrusion is also known to be importantto North during spring and summer and 3 km during fall in American bears (Jonkel and Demarchi 1984, Almack Yellowstone Park (Mattson et al. 1987). There is also 1985, Haroldsonand Mattson 1985). between 45 and 80% less use of ungulate carrionthan There is apparentlystill sufficient secure habitat in expected during spring within 400 to 1,000 m of high- eastern Europeto accommodatemajor bear population ways in Yellowstone Park, depending on presence of increases;whereas in Norway and westernEurope scar- cover (Green and Mattson 1988, Henry and Mattson city of secure habitat probably limits growth of relict 1988). In ShenandoahNational Park, males use areas populations (Zunino 1981, Elgmork 1988). European near all roads, and females near light-dutyand primary brown bear populationsconsistently and often dramati- 44 BEARS-THEIR BIOLOGY AND MANAGEMENT

cally increasedwhen protectedfrom huntingin Finland cubs-of-the-year(COY) by using relatively unoccupied (Pulliainen 1979, 1983), Estonia (Kaal 1976), the Volo- and typically less productive habitat (Pearson 1975, grad area (Kaletskaya and Filinov 1986), Poland Russell et al. 1979, Miller and Ballard 1982, Mattson (Buchalczyk 1980, Jakubiec and Buchalczyk 1987), 1987, and others),and by being extremely aggressive to Czechoslovakia(Sladek 1978), Bulgaria(Markov 1980), intruders.Then, when alone or when the cubs are more Rumania(Buchalczyk 1980), and Yugoslavia (Isakovic mobile, females use the most productiveavailable habitat 1970). The same has not been true of more isolated to recoup the incurredlosses (Eagle and Pelton 1983, populationsin Italy (Fabbriet al. 1983), the Cantabrian Mattson 1987). There are obvious exceptions to this Mountains (Clevenger et al. 1987), and the Pyrenees strategy, such as females with COY among other adult (Camarra1983, 1986). bearsat dumps and spawning streams; however, this class of females is consistentlyunderrepresented in these situ- DISCUSSION ations (cf. Horocker 1962, Stonorov and Stokes 1972, Egbertand Stokes 1976, Kendall 1986). Behavioral Framework I used the foregoing informationto rankbear classes To understandhow bears respond to humans, sorme in termsof characteristicunit-mass energy requirements generalitiesof how bearsrespond to each otherneed to be and security-dominance-mediatedaccess to productive established. There is considerablequantitative, inferen- habitat(Table 1). The differencebetween access rank(A) tial and anecdotalinformation available about bear be- and energy requirementrank (B) indicates the relative havior; there is also considerablevariation among sex predicamentof different bear classes in meeting their and age classes. Many behavioraldifferences appearto energy requirements.A lower (negative) rankindicates be size-mediatedand reflected in dominancehierarchies; greater stress and, perhaps, willingness to tolerate hu- this is obviously modified by individualpersonality and mans in the pursuitof food. As I mentionedbefore, lone experience, familial relationships, and the aggressive adult females may be much more highly motivated to defenseof young, (cf. Homocker1962, Egbertand Stokes feed, to replenish depleted adipose reserves, than strict 1976, Tate and Pelton 1983, Herrero 1985, Lunn and energy requirementswould indicate (i.e., their body fat Stirling 1985). cycle is probablymore meaningful viewed on a 2 to 3 In additionto size andexperienceper se, severalother year, ratherthan strict 1-year,basis). This rote calcula- majorfactors almost certainlyinfluence intra-and inter- tion also needs to be tempered by the likelihood that specific relationshipsof bears,including familiarity with securitytakes precedenceover all else for females with a given area(Klopfer 1962:60,Davies 1987:552)and the COY. By thisreckoning, females with young and subadult demandsof providingfood and securityfor offspring. In males are most likely to toleratehumans in the pursuitof termsof familiarity,subadult males areprobably the most both native and human-relatedfoods. disadvantagedof all bear classes due to long-rangedis- An additionalpopulation-level perspective is required persalfrom maternalranges (cf. Alt 1978, Garshelisand to interpretbear response to humansand their artifacts. Pelton 1981, LeCount1982, Klenner1987, Rogers 1987, The responseof any given bearpopulation is predictably and others) and young age; subadultfemales are more a functionof 4 main factors: (1) the natureand degree of likely to reside closer to or within the maternalrange. historical interaction with humans and human-origin Adultfemales probablyhave the greatestfamiliarity with foods, (2) bear populationdensity relative to ecological of the their ranges due to their age and the greaterintensity of carryingcapacity (K), (3) sex andage composition distributionof native home rangeuse implicitin smallerrange-sizes compared bearpopulation; and (4) productive to adult males (cf. Canfield and Harting 1987). On the habitatwith respectto humansand their facilities. Hunt- otherhand, adult females sustainthe undoubtedlyconsid- ing and frequency of contact are major variables in and influence how erableenergetic costs of providingfood and securityfor historicalhuman-bear relationships, humans of contact dependentyoung, evident in the energeticcosts of lacta- bearsview (Herrero1985). Frequency in a area is to tion (Sizemore 1980), the dependenceof reproductionon between bears and humans given likely due to chance alone food availability(Jonkel and Cowan 1971, Rogers 1976, increase as bear density increases, Bunnell and Tait 1981, LeCount 1982), and disparityof and the probableworsened energetic predicamentof an numberof bears The age-weightrelationships between males andfemales (Alt increasing (Keating 1986). propor- 1980b, Glenn 1980, Blanchard 1987, Kingsley et al. tions of adultand subadult males in a populationprobably interactions 1988, and others). Adult females apparentlyoften deal has the greatestramifications to bear-human et al. for with the demands of providing security especially for (cf. Young and Ruff 1982, Mattson 1987) HUMANIMPACTS ON BEAR HABITAT* Mattson 45

Table 1. Rank order of bear classes according to security-dominance mediated access to food and habitat (A), unit-mass energy requirements (B), and the relative predicament of bear classes in meeting their energy requirements (differences between B and A).

(A) (B) (B-A) Security-dominance Unit-mass Relative mediatedaccess energy requirements predicament

1. Adult males 1. Females with COY Adult males (2) 2. Lone adult females (lactation) Lone adult females (2) 3. Females with yearlings 2. Females with yearlings Subadultfemales (1) Subadultfemales (food-sharing) Subadultmales (-1) 4. Females with COYa 3. Adult males Females with yearlings (-1) (security mediated) Subadultmales Females with COY (-3) Subadultmales 4. Lone adult females (dominancemediated) Subadultfemales

a COY = cubs-of-the-year. reasons that I will addresslater. And distributionof the timber harvest, game management, and atmospheric most productive spring and fall habitat with respect to pollution. Bearshave been principallyaffected by greater humans has importantconsequences to the nature and spatial and temporal variation in pulses of bear food level of contactbetween humans and bears (Mattson et al. productionand by the elimination of high quality foods 1987). (e.g., spawningsalmonids, chestnuts, and whitebark pine nuts). The greatest divergence of contemporaryfrom Bear Response to Human-Caused primeval conditions in wildlands has occurred and is Habitat Changes likely to continue occurringin temperatePacific coastal Bears and humans are flexible, adaptableomnivores regions of NorthAmerica. In this ecosystem, bearshave and are naturalcompetitors. Both are capable of and a somewhat unique dependence on old-growth timber known to kill individualsof their own and other species (Lloyd 1979, Schoen and Beier 1986, Hamilton 1987), for food andto resolve conflicts. It is not unexpectedthat although Siberianand Yellowstone brown bear popula- competitionbetween bears and humansshould turnvio- tions are also dependenton old-growthstone pine forests lent, andthat each shouldpose some measureof riskto the for important food (Stroganov 1962; Bromlei 1965; other (MacPherson1965, McCullough 1982). Humans Ustinov 1965; Mattson and Jonkel, in press). Com- of technological societies have had the decided advan- poundingthis disruptivescenario is the prospectof whole tage over bears and have not tolerated any appreciable vegetationzones shifting, shrinking,and expanding with bear use of common foods, including wild game and warmingof the Earth'sclimate. fruits, and domesticatedlivestock and vegetal crops. Another critical factor that has influenced and will Even thoughhuman-origin bear foods have supplanted continue to influence bear populationresponses to hu- native bear foods on wildland converted to agriculture, man-effected changes in their habitat is the increased humanintolerance has typically precludedbear use. On isolation and fragmentationof bear populations. Al- the large scale, most humanfoods areunavailable in bear thoughbears are flexible animals,evolutionarily adapted habitatdue to the elimination of bears, and virtually all to variable environments(Herrero 1972, 1978; Kurten remainingbear populations depend on wild native foods. 1976:60), much of the species resilience must have de- Bear populationsthat rely heavily on humanfoods do so pended on free interchangeamong populationsfor natu- only in areaswhere sufficient securehabitat is available. ral augmentation of locally stressed populations and All use of human foods, regardless of importanceto a emigration into new areas. In many areas, bears are bear population,apparently depends on nearbyrefuge. endangered by population fragmentationand ongoing Human-inducedchanges in wildlandsare probably of habitatfluxes greaterthan any in the last 10,000 to 12,000 greater significance to surviving bear populations than years. Habitatavailable to a bearpopulation must be suf- introductionof exotic foods. Humans have disrupted ficiently large that perturbationscan be averagedacross otherwise stable, dynamically equilibratedprocesses in the landscape (Pickett and Thompson 1978). With his- virtuallyall wildlandecosystems occupiedby bears. This torical human alterations,the area necessary to accom- disruptionhas been effected primarilyby fire control, modate perturbationshas probably increased. More 46 BEARS-THEIR BIOLOGY AND MANAGEMENT populations are probablyat risk than managers would andthe occasional largeblack bear were primarybenefi- acknowledge,given thata mere5 yearsof dramaticlong- ciariesof remoteopen-pit dumps, subadult male grizzlies term change can look deceptively stable. and adultmale black bearswere the principalforagers at Humanattitudes can also dramaticallyinfluence the campgrounds,typically undercover of night, and adult ability of bearpopulations to respondto human-induced female black bears were the principalroadside panhan- habitat changes. This is illustrated by differences in dlers. Heavy harvestby humansnear dumps or habita- historicalhuman-bear interactions between Eurasiaand tions can removemost residentadult bears and instill fear North America. In both regions, bearshave been elimi- in the rest (Rogerset al. 1976). Underthis circumstance, nated from most of their former range. The greater subadult males may end up as primaryconsumers of currentproportionate overlap of bear populationswith edible garbage (cf. Rogers et al. 1976, Tietje and Ruff land intensivelyused andoccupied by humansin Europe 1983) or agriculturalcrops (cf. Gunson 1975). Subadult and China is very likely because Europeanbrown bears male use of dumpsmay also characterizethe peripheryof and Asiatic black bears are warier and less aggressive occupied bear habitat, given that they are the primary than their North American counterparts(Ognev 1931, dispersingclass and conceivably unacquaintedwith na- Curry-Lindahl1972, Zunino 1981). Cultureplays a part tive foraging options. in determininghuman tolerance of competitionand risk As a corollary,adult males apparentlymore often have froma largecarnivore, as clearlydemonstrated by human the prerogativeto use native foods fartherfrom humans. tolerance of the Bengal tiger (Panthera tigris) in India In Yellowstone Park, the richest fall foraging sites are (Schaller1967). In NorthAmerica, it is likely thatneither concentratedfarther from humans and receive greatest bears nor Europeansettlers had sufficient time to adjust use by adultmales (Mattsonet al. 1987). McLellanand to each other, as they probablydid to a greaterextent in Shackleton(1988a) suggest the same situationfor their Europe. The rate of habitat transformationin North BritishColumbia study area. However, in Yellowstone, America was rapidand was apparentlyaccompanied by food productionvaries considerablyamong years, and intoleranceto hindrancefrom bears or indigenous hu- during years of poor whitebark pine nut crops, rich mans (Storer and Trevis 1955, Cronon 1983, Brown foraging sites tend to be concentratedcloser to humans 1985). Dramaticalteration of habitatcaused by introduc- (Mattsonand Knight 1989). tion of livestock, eradicationof native game, increased Given the very likely pivotalrole thatadult males play fire frequencyand severity, and conversion of wildlandto in habitatselection, adultfemales and subadultmales are agriculturewas accompaniedby widespreadand deliber- probably more often left to use sites less secure from ate killing of bears. Ironically, in the past as well as humansfor feeding on humanor richnative foods. Also, present,human-caused habitat alterations probably con- these bearclasses probablyhave the motivationto feed in tributesubstantially to conflicts usually rationalizedby areas less secure from humans;not uncommonly,adult humans as due to the "irascible"and "irredeemable" females, females with young, and subadultmales have nature of bears (Bailey 1931, Storer and Trevis 1955, been observed to forage nearest to humans, especially Brown 1985). Rate of habitat change and concurrent when rich native foods were at stake. The nearness of human attitudes almost certainly synergistically affect humans may serve as a refuge from adult males, espe- the ability of bear populationsto persist in bear habitat. cially for subadultmales and females with young; and where black and grizzly bears coexist, the nearness of Bear Response to Humans humansmay also serve as a refuge for black bears. had and continues to Apparently,adult males more often have prerogative This disportmentof bears has on the best human foods (i.e., dumps rich in edible have consequences. Because adultfemales and subadult nearhumans out garbage)in settingsfarther removed from humans. This males seem to moreoften end up feeding classes more often is probably less of an individual and more of a class of necessity or by default, these to humans et al. phenomenonwhere humanfoods are more importantto comprise bears habituated (Mattson This is a a bear population. Under circumstanceswhere human 1987, Olsen et al. 1987, Warner1987). gener- foods arecritical or at least very important,as in Yellow- alization,given thatadult males areknown to habituateto stone Parkbefore 1970 and in Newfoundland,both adult humans(Herrero 1985). Still, in many regions, propor- male and lone adultfemale classes make substantialuse tionately more adult females and subadultmales come as risks humans of dumpsor hand-outs.In YellowstonePark before 1970, into conflict with, or are perceived by, therewas a hierarchyof access to humanfoods based on becauseof habituation.In areaswhere both grizzlies and bears for the same reasons quality and securityof the foraging site. Adult grizzlies black bearsrange, black may HUMAN IMPACTS ON BEAR HABITAT * Mattson 47 fall into this "bad bear"category (cf. Barnes and Bray humans. Habituationentails less fear of and greater 1967, Mundyand Flook 1973). Consequently,subadult proximity to humans (K. Jope, pers. commun.), and so males andadult females aremore often killed by humans, may allow bearsto use otherwiseunavailable but impor- especially in areaswhere the bearpopulation is protected tant foraging sites near humans. Habituationis more from hunting (cf. Craigheadet al. 1988). Where bear likely to functionin this mannerin populationsat or near populationsare huntedand where livestock predationis ecological carrying capacity. But especially for more a major source of conflict between humans and bears, aggressive bear species or populations,habituation en- males aremost proneto removal(Bunnell and Tait 1985, tails greaterrisk of injuryto humansand food condition- Auneand Brannon 1987, McLellan and Shackleton 1988b, ing aggravatesthis risk (Herrero1985). For this reason, andothers). The consequenceof these interactionsamong habituatedbears have been selectively eliminated by bears is that adult females and subadultmales may be humans. However, the remainingwarier bears are more advantagedin the shortterm by a certainlevel of human likely to avoid humans and their facilities, and overall presence, but the longer term probablyresults in lower habitateffectiveness (i.e., behaviorallymediated access) survivorshipfor both classes. and carryingcapacity almost necessarily declines (Keat- For reasons outlined above, adult males may partly ing 1986). This may not be a significant factor where regulatethe level of habituationand humanfood use in human densities are low and bears are not extremely bear populations. Subadultmales typically avoid adult wary,but in areaswith high or increasinglevels of human males, presumablydue to overt aggressionon the partof use andwith continuedcropping of habituatedbears, loss the adults(Bunnell and Tait 1980, Young andRuff 1982, of "effective" carryingcapacity will compound the ef- Rogers 1987). Influx of subadultmales may resultfrom fects of mortality. removalof adultmales on a large or small scale (Young This predicamentis more likely for brown and polar and Ruff 1982, Tietje and Ruff 1983). In the absence of bearsthan for Asian andAmerican black bears. Thereare adult males, subadult males probably exist at higher differences in aggressiveness and consequent risk to densities (Young and Ruff 1982) and may more often humansbetween these 2 groupsof bearsthat precipitate forageon humanfoods, whethergarbage or crops. These different levels of retaliationfrom humans (cf. Jonkel 2 factorscould resultin a much higherincidence of crop 1970; Herrero1972, 1978). The Europeanbrown bear damages and humanfood use on the fringe of occupied could be innately so wary that density of humansalone bear habitat, where adults have been eliminated, com- may influencepopulation viability, even in the absenceof paredto areaswhere the adultsegment is intact. This may hunting. It may be possible, although unlikely (Pelton explain the high level of apiary and grain crop use 1987), for humansto intensivelyuse landand have viable principallyby subadultmales in the Peace Riverregion of bearpopulations when dealingwith the opportunisticbut Albertaduring the 1970's (cf. Gunson 1975). Ironically, typically less aggressive black bear. The same is proba- as long as a productivebear populationpersists in sur- bly not true of polar and North Americanbrown bears, roundingareas, a high level of bearharvest in agricultural given thataggressiveness and the ability to habituateare districtswill probablynot alleviate and may even aggra- apparentlyinnate (Rasa 1987) and complexly associated vate the depredation problems. On a smaller scale, with the basic behavior of these species (Jonkel 1970; removal of some adult males from a populationat large Herrero 1972, 1978). Innate aggressiveness and the might give other bears more short-termoptions, with ability to habituatecan perhapsbe selected against and resultingfewer front-countryproblems for an uncertain reducedon the orderof evolutionarytime, but probably but probablyshort period of time. Thus, the observation not on the orderof decades,as has been impliedby Dood thatfewer bear-humanconflicts characterizehunted bear et al. (1988) andMeagher and Fowler (1989). This seems populations(Herrero 1985, Dood et al. 1988) may reflect especially likely given that bears apparentlyrespond to both greaterwariness among bearsand a greaternumber humans much as they would to other bears (C. Jonkel, of optionsfor subordinateor security-consciousbears; in pers. commun.) addition,a huntedpopulation is more likely to be below This review has demonstratedthat (1) humans and ecological carryingcapacity, and bears at largeare proba- bearsare naturalcompetitors, (2) bearhabitat and popu- bly betterable to avoid humansand meet theirenergetic lations will continue to be subject to disturbanceand needs becauseof greaterintraspecific individual "space" change,and (3) unless given no optionor attractedby rich (cf. Nagy and Haroldson 1990). foods, bears generally try to avoid humans. If humans Habituationper se has major implications to bear desire brownand polarbear populations that are capable populations confronted by even moderate densities of of survivingongoing andimpending major habitat distur- 48 BEARS-THEIRBIOLOGY AND MANAGEMENT bances, then we retainonly 2 options:either (1) increase and investigation. Mont.Dep. Fish, Wildl. andParks Rep. humanuse of occupied bearhabitat and accept the con- 138pp. , ANDB. BRANNON.1987. East Front studies. comitantincreased risk of injuryassociated with preserv- grizzly Mont. Dep. Fish, Wildl., and Parks. 146pp. ing habituatedbut hopefullynot food-conditionedbears, AYRES,L.A., L.S. CHOW,AND D.M. GRABER.1986. Black bear or (2) continueto crop habituatedbears, and maintainan activity patterns and human induced modifications in expanse of wildernesshabitat preserved from significant Sequoia NationalPark. Int. Conf. BearRes. and Manage. human intrusion. Humans have characteristicallynot 6:151-154. AZUMA,S., ANDH. TORII.1980. of humanactivities on acceptedthe risksentailed the first andso Impact by option, long- survivalof the Japaneseblack bear. Int. Conf. Bear Res. term of brown preservation andpolar bear populations is and Manage. 4: 71-79. likely to be contingent on preservation of wildlands BAILEY,V. 1931. Mammalsof New Mexico. NorthAm. 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