Factors Affecting the Evolution and Behavioral Ecology of the Modern Bears Author(s): Ian Stirling and Andrew E. Derocher 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. 189-204 Published by: International Association of Bear Research and Management Stable URL: http://www.jstor.org/stable/3872919 Accessed: 03/01/2009 19:54

Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use.

Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http://www.jstor.org/action/showPublisher?publisherCode=iba.

Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission.

JSTOR is a not-for-profit organization founded in 1995 to build trusted digital archives for scholarship. We work with the scholarly community to preserve their work and the materials they rely upon, and to build a common research platform that promotes the discovery and use of these resources. For more information about JSTOR, please contact [email protected].

International Association of Bear Research and Management is collaborating with JSTOR to digitize, preserve and extend access to Bears: Their Biology and Management.

http://www.jstor.org FACTORSAFFECTING THE EVOLUTION AND BEHAVIORAL ECOLOGY OF THE MODERNBEARS1

IAN STIRLING,Canadian Wildlife Service, 5320 122 St., Edmonton, Alberta, T6H 3S5, and Department of Zoology, University of Alberta, Edmonton, Alberta. T6G 2E9 ANDREW E. DEROCHER, Department of Zoology, University of Alberta, Edmonton, Alberta. T6G 2E9

Abstract: The present distribution and abundance of the ursids is but an ephemeral reflection of an evolutionary path that began with the first identifiable bear, the dawn bear (Ursavus elmensis), 20 million years ago in the early Miocene epoch. Although the dawn bear was only the size of a fox terrier, by the Pleistocene its descendents had evolved into some of the largest terrestrial carnivores the world has known. Most bear species evolved in the northern hemisphere although some dispersed and reached South America, Africa and SoutheastAsia. Each species had to cope with ecological changes that affected interspecific competition or the availability of food. Apparently the black bear was sufficiently adapted to have survived largely unchanged from what it was like a million years ago. Numerous species went extinct, leaving only the 8 still present today. Some understand- ing of the evolutionarypressures that the modem bearshave evolved throughmay help us to understandtheir behavioralecology. During the Pleistocene, bears at higher latitudes grew large and ecologically plastic while those closer to the equator remained small and became ecological specialists, as predicted by Geist's (1987) dispersal theory. Adaptations of the teeth of ancestral bear species allowed them to be both herbivores and carnivores. This allowed them to develop large size and broad ecological plasticity. Large body size enabled bears to conserve heat, capture large prey, defend carrion, travel great distances, and, as vegetation increased in the diet, to survive on qualitatively poorer food. Quantity and quality of available food and the degree of sexual dimorphism influenced the size of the home range and the evolution of social behaviorin each species. Bears show a great deal of individual variation in behavior and may exploit different subniches as a result of learned behavior. Slight differences in phenotype may also influence exploitation of subniches. Recent literature indicates that some terrestrial bear species are more active predators than previously thought and some evidence suggests a degree of scaling between the size of bears and the size of their prey. Social signalling appears to have been influenced by life in forest habitats but is not well understood. We give a preliminary interpretation of the social organization of the present day bears through the interactive framework of proximate ecological pressures, phylogenetichistory, and learning. There are likely few populations of bears anywhere in the world whose behavior has not been significantly influenced by man. This may confound our understanding of their behavior and ecology. Remaining populations of bears may not be able to adapt successfully to the combined effects of human predation, disappearing habitat, and climatic change.

Int. Conf. Bear Res. and Manage. 8:189-204

The bears are a fascinating group to analyze in an and, in the northernhemisphere, the biomass and diver- evolutionarycontext because of the remarkablevariation sity of plants suitable for ungulates reached its zenith in their adaptations. The largest species are about 10 (Guthrie 1984). Savannas and steppes became wide- times heavier than the smallest. The degree of sexual spread. At higher latitudes and altitudes the climate dimorphismranges from species with none to those in amelioratedand vegetation became abundant during inter- which males are twice the size of females. Bears have glacial periods. Mammalgroups such as ungulatesdis- evolved specializedniches as carnivores,herbivores, and persed,speciated, and becamelarger (Geist 1978, 1987). myrmecophages,while retainingthe functionalability to During this period, the first identifiablebear species of be omnivores. Pandas,which normallyeat only 2 species the genus Ursus, U. minimus,appeared in the late Plio- of bamboo will still eat meat, while polar bears, which cene deposits of Europe. It probablygave rise to the specialize in hunting seals, also eat berries. The home present day members of the genus as well as several ranges of different species can range from less than 10 extinct species. km2to over 100,000 km2. Coincidentwith this largeincrease in the biomassand The present day distributionand abundanceof the diversity of prey species, there was an explosion in the ursids is but an ephemeralreflection of an evolutionary diversityof predators.From the late Pliocenethrough the path that began with the appearanceof the first identifi- Pleistocene,the bearsspeciated and evolved into some of able bear,the dawnbear, 20 million yearsago in the early the largest terrestrialcarivores known (Kurten 1968, Miocene epoch (Kurten 1976). Consequently,a brief Kurtenand Anderson1980). Duringthis period,several examinationof the evolutionaryhistory of moder bears species of bearsevolved, dispersed,and disappeared. An may help in interpretingthe available informationon importantpoint is that many more species once existed theirpresent day behavioralecology. The dawnbear was thando today. Forexample, severalspecies of the genus only about the size of a fox terrier,but even after 10 Tremarctoslived in southeasternNorth America (e.g., million years, its descendent Protursus, from the mid- the Floridacave bear,T.floridanus) and SouthAmerica. Miocene of Europe,was only modestly larger. Today only the spectacledbear (T. ornatus) survives in About 5 million years ago in the mid-Pliocene the the northernAndes. Similarly, the large short-faced worldclimate became drier (Kurten 1976, Guthrie1984) bears(Arctodus spp.) of NorthAmerica, the cave bearsof Eurasia Ursus in Invited paper (e.g., spelaeus Europe),various popula- 190 BEARS-THEIR BIOLOGY AND MANAGEMENT

tions of brown bears (U. arctos) in Europe, Asia, and THE SIZE OF BEARS NorthAfrica, and the Langebaanwegbear (Agriotherium The modem bears are all medium- to large-sized africanum)of South Africa (Kurten 1966, 1967, 1968; mammals,ranging from 27 kg for the female Malayan Hendey 1977) all thrivedand subsequentlywent extinct. sun bear (U. malayanus)(Nowak and Paradiso1983) to In generalthough, the bearswere most successful where over 800 kg for an exceptionallylarge male polarbear in they originated,in northtemperate areas. primecondition (DeMaster and Stirling 1981). The latter Each species had to cope with a series of climatic representsa remarkableincrease in body size, relativeto changesthat in turnaffected interspecific competition or their small Miocene ancestor,the dawn bear,20 million alteredfood availability. A few, such as the American years ago. About 15 million years later, when Ursus black bear(U. americanus),were sufficientlyadapted to minimusfirst appeared,it weighed approximately50 kg, survive changingecological conditions and exist today, similarto the maximumweight of the male Malayansun largely unmodifiedfrom what they were like a million bear,the smallestof thepresent day ursids. Kurten(1976) yearsago. Thebrown bears and polar bears (U. maritimus) noted thatits canines were thin and sharpbut the molars of todayare morphologically similar to, thoughsmaller in had already become enlarged and better adapted for size, than their Pleistocene ancestors(Kurten 1976). feeding on vegetation, adaptationsthat together may An importantconsideration when analyzing the be- have madeit possible for the bearsto evolve a largebody. havioralecology of the presentday bears is the possible Even when the smallerspecies of bearsare included, effect of man. Because of incessanthunting and habitat the ursidsare significantlyheavier than all otherfamilies change, it is likely that few remaining populations of of carnivores (Gittleman 1985). Clutton-Brock and bears behave quite as their ancestorsdid. For example, Harvey(1983) summarized4 majoradvantages of large largenumbers of brownbears were once a common sight body size: the abilityto producelarge neonatesor litters, in continentalNorth America (Storer and Tevis 1955). reductionof relative heat loss, the ability to catch and Can we assumethat the habitatpreferences and behavio- handlelarger prey or travelgreater distances in searchof ralecology of remnantpopulations in places like Yellow- food, and the ability to survive on qualitativelypoorer stone or southeasternBritish Columbia are unchanged food. Except for the productionof altricialoffspring in from those of their predecessors? Probablynot, but it small litters,an anomalyimposed by physiological con- may not be possible to evaluate the changes that have straints(Ramsay and Dunbrach1986), all these advan- takenplace. Similarly,the habitatoccupied by remnant tages wereprobably important to bearsin theevolution of populationsof other species may be significantlydiffer- large body size. ent from that in which they originally evolved. Obvi- Reductionof the ratioof surfacearea to volume with ously, we can only workwith the informationat handbut increasedbody size would have aided thermoregulation we need to remainconscious of possible biases. in an increasinglyseasonal climate at higherlatitudes. In In this paper,we have followed the taxonomyoutlined this respect,the increasedbody size of bearswas consis- by Nowak and Paradiso(1983) in which the giant panda tentwith trendsin otherIce Age mammals. In an analysis (Ailuropodamelanoleuca) is considered an ursid. We of the evolutionof Ice Age mammals,Geist (1987) noted refer to all races and populationsof U. arctos as brown that speciation of cervids and caprids followed predic- bears and group other bears, except for the spectacled tions made by his dispersaltheory. In particularspecies bear, into the genus Ursus. thatcolonized higher latitudes with increasinglyseasonal Several organizationshave supportedour research climates where productivitypulses became larger, be- over the years, which in turngave us the experiencethat came more ecologically plastic, and developed more made it possible to write this paper. In particular,we ornatesocial organs(e.g., hornsand antlers). In contrast, acknowledgethe CanadianWildlife Service, PolarCon- dispersalinto lower latitudeenvironments with less sea- tinental Shelf Project, World Wildlife Fund (Canada), sonalvariability led to paedomorphism(i.e., theretention NaturalSciences and EngineeringResearch Council of of primitiveness)and ecological specialization. As was Canada,the ArcticPetroleum Operators Association, and the case for the ungulategenera studied by Geist (1987), the Departmentof Zoology and the Boreal Institutefor the biggest bearswere also northtemperate species of the NorthernStudies of the Universityof Alberta. We thank late Pleistocene, such as the cave bearof Europeand the M. Meagher,T. 0ritsland, B. Peyton, M. Rosenthal,D. short-facedbears of NorthAmerica (Kurten 1976). The Ruben, and D. Weinhartfor permission to cite unpub- largestmoder ursidsare also northtemperate species. In lished observations.M. Ramsayand 2 unidentifiedrefer- comparison,the bearsin sub-tropicalclimates (sun bear, ees providedconstructive reviews of the manuscript. slothbear [U. ursinus],and spectacled bear), and the giant EVOLUTIONOF BEARS * Stirling and Derocher 191 panda of southeasternChina, were removed from sea- ground, trees, or thick vegetation. To survive in open sonal pulses in productivity. All are smaller than their habitat, a mammal must be able to defend itself from northernrelatives, less sexuallydimorphic and most have predatorsor be fast enough to escape them. Conse- become ecologically specialized (Laurie and Seiden- quently,as the body size of some bearspecies increased, sticker 1977, Schalleret al. 1985, Lekaguland McNeely they probably occupied more open habitat for longer 1977). periods, and were able to increase the proportionof It may be thatbears were capableof broadecological vegetationin the diet. Their largersize also made them plasticitybecause the morphologicaladaptations of their betterable to defend themselves from predators.As the teeth allowed them to evolve into a niche combining diet became progressivelymore vegetative, therewould herbivoryand predation(Kurten 1976). Their grinding have beencontinuing pressure for body size to increaseso post-canineteeth enabledthem to process large amounts enough vegetation could be ingested and processed to of vegetationin the seasonalpulses of high productivity. substitute for a high quality diet of animal material. However,the digestive tractof extantursids is not highly Largerbody size also made it possible to travel more in modified from that of other carnivorous mammals search of patchy food resources and to store and carry (Bunnell and Hamilton 1983), which may have influ- morefat with which to surviveduring periods of seasonal enced body size. In a study of digestibility of different or unpredictablefood shortage.With increased body size diets by 2 captive brown bears, Bunnell and Hamilton and well-developedcanines, some bearswere able to kill (1983) demonstratedthat digestive efficiency declinedas ungulates and other mammals, defend carrion from the proportionof vegetationincreased. In particular,they competitors,and protect themselves from other preda- noted that cellulose was poorly digested, especially in tors. Throughthis uniquecombination of being able to be comparison to meat. Similarly, Schaller et al. (1985) predators,scavengers, and herbivores,they were able to found that dry matterdigestibility of bamboo leaves by exploit several food bases. pandas varied seasonally between only 12 and 23%. Smallpredators are restricted to smallprey, so thatone Pandas are able to obtain carbohydratesby digesting benefitof being largeis thatan animalcan kill both small hemicellulosefrom the cell wall of the plantsbut, as in all and large prey (Gittleman 1985). For example, brown bears,they cannot digest cellulose. In comparison,Sin- bearsare capableof takingadvantage of relativelysmall clair (1975) found that ungulates living on green grass animals such as groundsquirrels and salmon in circum- assimilate about 80% of theirdiet, including40-60% of stances where their abundance makes such behavior thecellulose andhemicellulose (Van Soest 1982). Guthrie energeticallyor nutritionallyworthwhile (e.g., Stonorov (1984) noted that non-ruminantscannot usually extract and Stokes 1972, Murie 1981). Even so, the ratio be- all the necessary amino acids, fatty acids, vitamins, and tween the size of the bearand its prey may be misleading other vital dietary constituents from 1 or 2 species of since the predator'slarge size may be necessaryto move plants. Consequently,he speculatedthat as non-rumi- heavy stones or earthto catch groundsquirrels or to stay nantsmoved towardincreasing proportions of vegetation warmwhile standingin cold waterfor protractedperiods in the diet, they probablyhad to move over largerareas to while fishing for salmon. In the case of the morecarnivo- find a variety of plant species to provide all the require- rous bear species, their maximum size may have been ments. The same would apply if there was only a small influenced by the maximumsize of generally available numberof digestible species but they were widely dis- prey, as will be discussed belpw. tributedat low density,in discontinuouspatches, or both. Although Guthrie (1984) was speculating about the evolution of groundsloths, the same could have applied SEXUAL DIMORPHISM to theancestral ursids. As thenon-ruminant bears evolved Sexualdimorphism is stronglyassociated with polygy- into a progressivelymore herbivorousniche, they would nous breeding and is classically thought to result from likely have needed larger home ranges to ensure an sexual selection. Trivers(1972) proposedthat variation adequatevegetative food base andallow for seasonaland in the degree of parentalinvestment was the principal annualvariation in its distributionand productivity. factorthat determined if an animalbred monogamously A vegetative diet alone is not a sufficient stimulusto or polygynously. However,in a subsequentreview, Ralls producelarge size, as is illustratedby several successful (1977) noted thatmuch of the theoryabout the evolution taxa of small mammals. Small animalsare more vulner- of sexual dimorphismwas based on avian models and able to predationthan are large ones so they need to was not as applicable to mammals. In particular,she remain adjacent to escape habitat such as holes in the found that although a high degree of investmentin the 192 BEARS THEIR BIOLOGY AND MANAGEMENT

- offspringby bothparents was a good predictorof monog- 2.5 amy, the converse was less reliable. In addition, the 0 0. of investment does not 0 degree parental explain why 2- * sexual dimorphismhas evolved more frequentlyin large O mammalsthan in small ones. ~**"OH in the * o Sexual dimorphismin body size is present all . 1.5- o 0 modem ursids the sloth for which 0 except possibly bear, O 0 0 0 thereare too few dataavailable to be certain As _0 (Table 1). * faras we have been able to determine,sexual dimorphism I characterizedmost of the extinct Pleistocene bears as well. o -t- In general, sexual dimorphism increases as species -j 0.5- Legend * BLACKBEARS become (Clutton-Brocket al. 1977). x larger Although 0 BROWNBEARS quantitativeweight dataare not availablefor most bears, * POLARBEARS n l I sexual dimorphismtends to increase with size in the 3 0 50 100 150 200 250 300 350 400 species of North American bears (Fig. 1). However, in WEIGHTOF MALES(kg) the 3 North America the of sexual species, development Fig. 1. Sexual dimorphism of black, brown, and polar bears as a function of body dimorphismis only significantlydifferent between black size. Black bear weights from Bunnell and Tait (1981); brown bear weights from and bears test P < It is also Interagency Grizzly Bear Committee (1987); polar bears weights from Lone polar (Tukey's 0.05). (1970) and Canadian Wildlife Service unpublished data. Line indicates regres- particularlyinteresting to note that a similar patternof sion line for North American brown bear populations (slope of regression is sig- than 1 increasing sexual dimorphismin relation to increasing nificantly greater (P< 0.05)). body size is present in North American brown bear populations(Fig. 1). phismin the size of the body andthe canineteeth of males, The bears did not develop anything resembling the especially in the north temperatefossil and extant spe- antlersof the Ice Age ungulates(Geist 1987). However, cies, functionfor display, threat,and fighting. Kadosaki we suggest the significantdevelopment of sexual dimor- et al. (1986, 1989) compared the skull morphology of brown bears and Asiatic black bears (U. thibetanus)in sexual was Table 1. Weights and approximate degree of sexual dimorphism in bears.a Japan.They foundthat, although dimorphism detectable in all measuredparts, the difference was sig- nificant in the canine teeth. In both species, they Mean weight only (kg) found the of sexual went from Species Males Females Ratio (male:female) degree dimorphism great- est to least in the following characters:canines, teeth Sloth bear 55-145 >1.0 except canines,length of toothrows, andskull size. Since Giantpanda 97-107 86-89 1.1 to 1.2 the diet of males and females of each species is similar, Malayansun bear 27-65 approximately1.2 the significantenlargement of the canine teeth in males, Giant short-facebear 350-375 250-270 approximately1.4 beyond that which would be expected because of their Spectacled bear 140-175 110-120 approximately1.4 larger size, probablyfunction for intrasexualthreat dis- Americanblack bear 82-165 58-95 1.5 (range 1.1-1.7) play and weapons. For example, in male polarbears, the Brown bear 145-389 93-207 1.6 (range 1.2-2.2) canine teeth are importantin intraspecificagonistic be- Asiatic black bear 110-150 65-90 1.7 havior. The canines of males are often badly broken in in Polar bear 271-322 147-197 1.8 (range 1.6-2.0) intraspecificfighting; a featurethat is absent females and more Europeancave bear 410-440 205-220 approximately2.0 (Ramsay Stirling 1986). Similar,though exag- of canine teeth characterizedother Floridacave bear 230-250 115-125 approximately2.0 gerated,development Pleistocene predators, such as the saber-toothed cats a Data for American black bear from Bunnell and Tait (1981); polar (Smilodon (Kurtenand Anderson 1980), and likely bearweights basedon a randomsample of 100 adultmales and 100 adult spp.) females from Svalbard and 4 different populations in the Canadian also functionedpartly for social display. Arctic (L0n0 1970; Canadian Wildlife Service, unpublished data); Intenseintraspecific conflicts between adultmales of brown bears from InteragencyGrizzly Bear Committee (1987); spec- several species of bears have been reported (e.g., sun tacledbear from M. Rosenthaland D. Weinhart and (unpublisheddata) bears,Laurie and Seidensticker 1977; bears, Nowak and Paradiso (1983); other extant species from Nowak and polar Ramsay Paradiso(1983); and,forextinct species fromKurten (1967) andKurten and Stirling 1986) and, although conclusive evidence (1976), based on estimates of body size. relative to mating success is absent, it seems likely that EVOLUTIONOF BEARS * Stirling and Derocher 193

large body size confers reproductiveadvantage when females it might put them at a competitivedisadvantage competing with conspecifics. Bunnell and Tait (1981) when feeding on thin stems or the ends of branches.This also suggestedthat the largersize of male ursids,relative may also be a factor influencing sexual dimorphismin to females, may have evolved in partto favor the estab- bears. Even thoughthere are few reliabledata on weights lishmentof largerhome rangesand a subsequentincrease of adultmale andfemale sun bears,sexual dimorphismis in potential mates (see Table 2). Ramsay and Stirling reduced and both are apparentlyquite arboreal(Laurie (1986) speculated that intense intrasexualcompetition and Seidensticker 1977). Male and female sloth bears between male polar bears for females, caused by the and giant pandasare of similarsize and both are capable somewhat unpredictabledistribution of females on the climbers, though they mainly feed on the ground. Fi- moving sea ice and the consequentinability of males to nally, the least sexually dimorphicof the 3 NorthAmeri- defend areasthat would reliablyinclude oestrus females, can ursids(Fig. 1, Table 1), the blackbear, also makesthe resulted in greaterintrasexual competition for females greatest use of trees. The spectacled bear and Asiatic thanis found in terrestrialbears. Further,they suggested black bearexhibit a similardegree of sexualdimorphism that the marked sexual dimorphismin polar bears is a to the Americanblack bear (Table 1), feed arboreallyin consequence of the intense intrasexualcompetition be- some areas, make nests in trees to aid feeding, and tween males for breeding opportunitieswith females. sometimesrest in the nests as well (Schaller1968, Peyton However, their hypothesis does not explain the appar- 1980). The spectacledbear is much less sexually dimor- ently similar degree of sexual dimorphismexhibited by phic thanwas its extinctnearest relative (Table 1), which some populationsof brownbears (Fig. 1), or the extinct may have been influencedby feeding arboreally. terrestrialEuropean and Florida cave bears(Kurten 1966, 1967). An alternatehypothesis is thatthe terrestrial large BEARS AS PREDATORS Pleistocenebears, the large-bodiedpopulations of brown The degree of active predationby the 3 bear bears, and the polarbear simply reflect the trendtoward species found in North America varies from the carnivorous greaterdimorphism with increasedbody size (Clutton- bear to the less brown and black bears. Brock et al. 1977). polar predatory Because of theirextensive use of vegetation,brown and One otherecological factormay have hada significant blackbears have not generallybeen thoughtto be influence on the developmentof sexual dimorphismin signifi- cant predators.However, several more recentand the bears. Clutton-Brockand Harvey (1978) reported quan- titative studies have forced this to be revised thatwithin the primates,sexual dimorphismis greaterin premise (e.g., Cole 1972, Franzmannet al. 1980, Stewart et al. terrestrialthan in arborealspecies. They suggest this is 1985, andGarer et al. and because increasedweight does not influence intersexual Reynolds 1987, Boertje 1988, other papersin this volume). competition for food in ground dwelling species. In Throughoutthe carnivores,there is a correla- contrast, if males of arborealspecies were larger than strong tion betweenthe size of a predatorand the size of its prey Table 2. Home range sizes of adult bears. (Rosenzweig 1966, Gittleman1985, Vezina 1985, Earle 1987) that,at firstglance, mightnot appearto applyto the bears. For example, the polar bear seems 'oversized' Meanhome range (km2)(S.D.) when comparedto its majorprey, the ringedseal (Phoca Species Males Females hispida) (Fig. 2). Similarly,brown bears in severalareas make Giant pandaa 8.5 (0.9) 4.6 (0.6) extensive use of small prey. However, when the of each of bearis in relationto Asiatic black bearb 12.6 (9.1) weight species plotted the weight of the largest prey it is now known to take Americanblack bear' 81 (55) 27 (20) regularly,the relationshipfor solitarycarnivores derived Brown beard 631 (442) 242 (186) by Earle (1987) fits fairly well (Fig. 2). The largest Polar bearf - 96,924 (78,453) regular,though less frequentlycaptured, prey species of a Schalleret al. (1985); Johnsonet al. (1988) the bear is the b polar beardedseal (Erignathusharbatus) Hazumi and Maruyama(1986) c (Stirlingand Archibald 1977, Smith 1980), which Alt et al. (1980), Amstrupand Beecham (1976), Garshelisand Pelton weighs up to about360 In occa- (1981), Hellgren and Vaughan(1987), LeCount (1980), Lindzey and kg (Kelly 1988). addition,they Meslow (1977), Manville (1983), Pelchat and Ruff (1986), Reynolds sionallykill whitewhales (Delphinapterus leucas) weigh- and Beecham (1980), Rogers (1987a) ing up to about600 kg (Lowryet al. 1987, Smithand Sjare d Bear Committee InteragencyGrizzly (1987) 1990), and walruses (Odobenus to about e Amstrup 1986 rosmarus)up 500 kg (Kiliaanand Stirling 1978). 194 BEARS THEIR BIOLOGY AND MANAGEMENT

On the basis of circumstantialevidence and an ob- 2 subadultbrown bears that drew blood 1000 served attackby from a lone adult bison (Bison bison), brown bears are suspected to occasionally kill young bison, although none has been confirmed (M. Meagher 1973 and pers. A CY) 100 Legend commun.). Observationshave also been madeof individ- * WHITEWHALE ual brownbears lone bison them t/) X WALRUS testing by approaching + + O BEARDEDSEAL andthen when the bison them,refused to >- leaving ignored n v v V + RINGEDSEAL c. run, and on (M. commun.). O MUSKOX kept feeding Meagherpers. 10 A CARIBOU Healthyadult male bison may be too largeand well armed * ELK for a bearto attackwithout risk of seriousinjury to itself. * MOOSE V MOOSECALVES Testing likely helps a bear to identify a sick or weak O DEERFAWN animal. Bison also have a clumped distribution,espe- X GRNDSQUIRREL l ...... I l I K . l X l ...... P EDII.S. OI I l. duringcritical periods such as calving (Calef and 10PREDATOR 100 o000 cially PREDATORMASS (kg) Van Camp 1987), which may also make predationby Fig. 2. Size of known prey of black, brown, and polar bears plotted in relation to bears difficult. In a review of historical material, Roe the regression line of body weight of solitary carnivores (Earle 1987) and the (1970) found evidence of brown bears scavenging on weight of their largest regular prey. References by prey species as follows: white whale, Smith (1980), Lowry et al. (1987), Smith and Sjare (1990); walrus, dead bison but it appearsthat predation was uncommon. Kiliaan and Stirling (1978); bearded seal, Stirling and Archibald (1977), Smith Black bearsalso demonstratepredatory behavior and (1980), Kelly (1988); ringed seal, Stirling and Archibald (1977); muskox (D. Ruben, pers. commun.); caribou, Reynolds and Garner (1987), Boertje et al. have been found to be significant predatorsof moose (1988); elk, Cole (1972); moose, Mysterud (1973), Franzmann et al. (1980), calves (Franzmannet al. 1980). The smallerbody size of Stewart et al. (1985), Boertje et al. (1988); deer fawn, Ozaga and Verme (1982), Mathews and Porter (1988); ground squirrel, Murie (1981). blackbears probably precludes them from being a signifi- cant predator on adult moose. Recently, it has also Boertje et al. (1988) reportedthat adult male brown become apparentthat black bears can be importantpreda- bears killed an average of 3.3 to 3.9 adult moose (Alces tors of neonate white-tailed deer (Odocoileus virgini- alces) (400-500 kg) per year whereaslone adultfemales anus) (Ozaga and Verme 1982, Mathews and Porter killed significantlyfewer (0.6-0.8 moose/year). Female 1988). The maximum size of prey taken regularly by brownbears with cubs killed no adultmoose. All classes black bears is not known but, from Figure2, it should be of bears killed moose calves but females without cubs about 151 kg for a 100 kg bear. The vulnerabilityof prey killed at a higher rate than did the other 2 groups. In the of differentsizes to predationby black and brown bears area studied, brown bears were primary predators of probablyinfluences niche separationbetween them. moose and killed 4 times more animalbiomass thanthey Peyton (1980) reportedseeing the hide of a woolly scavenged. Mysterud(1973) also reported2 adultmoose tapir (Tapiruspinchaque) with blunt scars from being killed by brownbears in Norway but the sex of the bears attackedby a spectacled bear. Villagers had found and was not known. killed the wounded animal. Although Tschudi (1844, Lone adultfemale brownbears killed an averageof 0.9 citedin Peyton 1980)reported that spectacled bears preyed to 1.0 caribou(Rangifer tarandus) per year in east central on deer, guanaco (Lama guanicoe), and vicufia (Vicugna Alaska(Boertje et al. 1988). Reynoldsand Gamer (1987) vicugna), there are,no supportingquantitative data. also documentedkilling of caribouby brownbears on the Recent studies of the energetics of polar bears also Alaskan North Slope. Most of the animals killed were suggestthat body size may have a significantinfluence on calves but some adultswere takenas well. Adult females how bearshunt. Hurstet al. (1982) found thatthe energy were involved in 64.7% of the chases but were only requiredfor the plantigradepolar bear to move is about observedfeeding on 37.3%of the carcasses,compared to double that for most other mammals. To move at the 58.5%for males. However, it is likely that severalof the modest speed of 7 km/hr,uses 13 times moreenergy than carcassesthat adult males were observedfeeding on were lying. This probablyexplains the polarbear's preference killed by other smaller bears (Reynolds and Gamer for lying and still-huntingfor seals (Stirling 1974, Stir- 1987). D. Ruben (pers. commun.) of Paulatuk,North- ling and Latour 1978). Lunn and Stirling (1985) calcu- west Territories,also observedan adultmale brownbear lated that unless a 320 kg adult polar bear captureda kill an adult female muskox (Ovihos moschatus) (ap- flightless snow goose in late summer in 12 seconds or proximately250 kg) near Fallaise Lake, NorthwestTer- less, it would cost the animal more energy that it would ritories,in 1984. gain if it was successful. The lower ratioof surfacearea EVOLUTIONOF BEARS * Stirling and Derocher 195 to volume, andheavier deposits of fat on adultbears (par- may also have influencedthe developmentof sexual di- ticularlymales and pregnantfemales) mean they can run morphism. As alreadynoted above, adult male brown muchshorter distances than subadults because they over- bears kill far more adult moose than do lone females, heatmore quickly and are unable to dissipateheat quickly whereasthe reverseis truefor the killing of moose calves. enoughto be able to continuehigh levels of exertion. Al- In the case of the sexually dimorphic and polygynous thoughthere are no data availableat presentto compare polar bear (Ramsay and Stirling 1986), the adult males the cost of locomotionof brownand black bears, we sug- appearto prey most frequentlyon beardedseals and oc- gest thatit wouldalso be easierfor smallerand leaner sub- casionallykill whitewhales. Fromdata collected through- adultsto runlonger distances than adults. If so, this would out the CanadianArctic, 93% (14/15) of the beardedseal probablymean that largeranimals would make most of kills thatwere found while still in thepossession of a polar theirkills aftera shortburst of runningfrom ambush, sim- bearwere being consumedby adultmales. Females pre- ilarto the lion (Pantheraleo). Coincidentally,the lion is dominantlykill the smaller(60 kg) ringed seal. Thereis the only other mammal known in which the metabolic some segregationof differentage andsex classes of polar cost of movementis aboutdouble that of most othermam- bearsby habitattype (Ramsayand Stirling 1986). Much mals (Chassin et al. 1976). Not surprisingly,Schaller of this appearsto resultfrom females with cubs minimiz- (1972) foundthat female lions caughtmedium-sized prey ing the risk of infanticideby avoiding adultmales. Con- twice as often as males. He suggested that the females sideringthe large degree of sexual dimorphismin polar were more successful on the faster medium-sizedprey bears, segregation might also be influenced by differ- because they were faster than the more cumbersome ences in the vulnerabilityof different sized species of males. prey. The relationshipsbetween brown and black bearsand Surpluskilling has been documentedin wolves (Canis theirprey may not be as simple as the regressionin Earle lupus) (Miller et al. 1985) and other carnivores(Kruuk (1987) or Figure2. We suggest thatbody size and ener- 1972). Similarly, surpluskilling of domestic sheep by getics are significantfactors in determininghow bearsof brown bears has been reported in Norway (Mysterud differentbody sizes huntungulates. Learning is probably 1975) and of harp seal pups (Phoca groenlandicus)off also important.We predictthat most kills made by adult the coast of Newfoundlandby polarbears (T. 0ritsland, males will be after a short rush from ambush or after pers.commun.). Lowryet al. (1987) reportedpolar bears stalkingto close range and that most kills that requirea killing several white whales at 1 location and leaving longerchase will be madeby adultfemales with cubs and some uneaten. In the CanadianArctic, we once observed by subadults. Thereis some supportfor this hypothesis. a polarbear kill a ringed seal, feed extensively on it and Cole (1972) noted that subadultor subordinateyoung then kill 2 more within the next hour but leave them bears appearedto be the most effective predatorson elk uneaten.It is not clearwhy animalsdo this. Althoughthe (Cervuscanadensis). He also reportedseparate incidents benefitto otherbears, particularly subadults, of scaveng- of elk being killed by 2 subadultbears hunting together in ing on the remainsis probablyconsiderable, this seems an chases that lasted 15 and 20 minutes each. On the unlikely explanation. AlaskanNorth Slope, only 1 of 17 brownbears of known Anotherdifference between bear species relatesto the age and sex observedchasing caribouwas an adultmale lengthof time spentprocessing a kill. Polarbears usually (Reynolds and Garer 1987). The remaining 16 chases feed once on a seal kill and then abandonthe remains, were made by adult females and subadults. which sometimes are substantial(Stirling 1974, Stirling For the omnivorous bears, sexual dimorphismdoes andArchibald 1977). The only exceptionsto this pattern not appearto conferbenefits in the areaof resourcesegre- of carcassuse area few adultmales thatwe have seen kill gation (Bunnell and Tait 1981). However, in the North an adult bearded seal and apparentlyremain with it, Americanbears, sexual dimorphismappears to become possibly for several days. In contrast,brown bears are more pronounced with increasing predatorybehavior well knownfor remainingfor severaldays withan animal (Fig. 1). Rails (1976) suggestedthat sexual dimorphism they have killed, or 1 they are scavenging(e.g., Boertjeet could be relatedto niche exploitationas well as to a poly- al. 1988). This differencein how long polar and brown gynous breeding social system. Sexual dimorphismin bearsremain with theirkills may also relateto the rateat birds of prey is thoughtto function partiallyto separate which preycan be capturedin each ecosystem, prey size, niches and reduce intersexual competition (Selander and gross energy value in relation to alternate food 1972). We suggest partialniche separationof males and sources,and the numberof potentialinter- and intraspeci- females could be importantin the predatorybears and fic scavengersthat might attemptto contest ownership. 196 BEARS-THEIR BIOLOGY AND MANAGEMENT

INTER- AND INTRASPECIFICCOMPETITION occupied by the brown bear. Brown bears crossed the Interspecific and intraspecificcompetition between Bering land bridge in the late Pleistocene and invaded bears,including predation (e.g., Miller 1985, Ross et al. western North America via Alaska, and presumably 1988), has been significantin theirevolution. Cubsof all continuedto exclude the black bear from the plains. the predatoryspecies of bears are sometimes killed by No brown bears occurredin eastern North America adult male conspecifics (e.g., Jonkel and Cowan 1971, duringthe Pleistocene. In this situation,the now extinct Taylor et al. 1985, Dean et al. 1986, LeCount 1987) as black bear(Ursus americanusamplidans) often became well as by othermammalian predators (e.g., Rogers and as large as brown bears and theirremains are still occa- Mech 1981, Ramsayand Stirling 1985, Paquetand Car- sionally mis-identified as such (Kurten and Anderson byn 1986). Intraspecificpredation has not been reported 1980). Presentday blackbears in easternNorth America for any of the subtropicalspecies of bears, although it are still largerthan theirwestern counterparts that share may occur. habitatwith brownbears. Kurten(1963) has speculated In a comparisonof black andbrown bears in different thatthe extinctionof the Floridacave bearand the eastern biogeoclimaticzones in NorthAmerica, Herrero (1978) short-facedbear (A. pristinus) may have been brought found that brown bears are consistently 1.5 to 2.0 times aboutby competitionfrom the largeeastern race of black the size of black bears. He furtherconcluded that black bears and invading brown bears from the north. In this bears had retained the forest dwelling niche of their context, althoughblack and brown bears first appeared ancestorswhile the brown bear moved to exploit more together in the fossil record in Europe about the late open habitattypes as well as forests. When faced with a Miocene or early Pliocene, only the brown bear exists serious threat,the strategyof a female black bear is to there today, possibly because it displaced its smaller send her cubs up a tree safe from danger,flee, andreturn competitor(Kurten 1976). for her cubs when the threathas passed. In contrastto Another open country habitat occupied by brown black bears,the largerbrown bears protect their cubs by bearsin NorthAmerica is the tundra,north of the treeline. standingtheir ground or attackingthe perceived threat In parts of northernCanada, Harington et al. (1962) directly(Herrero 1978). Althoughthe cubs arecapable of suggested thatbrown bearpopulations have diminished climbing trees, they apparentlydo so much less fre- as a result of overhunting. Coincidentally,Jonkel and quentlyin responseto dangerthan do blackbears. Female Miller(1970) noteda possible increasein the numbersof polarbears, which live in open habitat,also defend their black bears recorded in various tundraareas and sug- cubs by directattack, even if threatenedby an adultmale gested this might be because of reducedcompetition or twice her size or a helicopter hovering over her head. threatfrom brownbears. Along the southwesterncoast of Hudson Bay, where The otherforest dwelling bearsare able to climb trees polar bear family groups spend significant amounts of although the extent to which they do so varies. Spec- time on land during the late summerand fall, we have tacledbears and sun bears are excellent climbers and feed never seen cubs attemptto climb trees, even thoughlarge arboreally. Sun bearslack hairon the soles of theirfeet, trees are presentin some areas. In lieu of trees as escape which has been suggested to be an adaptationto aid habitatin the High Arctic, female polarbears with cubs, climbing (Bunnell 1987). Although pandas feed pre- andlone subadultsoften climb 100 m ormore up a hillside dominantly on the ground, unattendedyoung are still above the sea ice anddig a pit to lie in wherethey can see vulnerableto predation(Schaller et al. 1985). They use aroundthem before sleeping. This precautionappears to trees for escape habitatunder some circumstances,in- be in responseto the threatof intraspecificpredation. cluding when harassedby courtingmales, but the pres- A plausiblehypothesis to explain why the black bear ence of leopards(Panthera pardus), which are known to did not move out of the forestmay be thatit was not large kill pandasoccasionally, may reducethe overallvalue of enough to protect its young, or possibly itself, on the that escape strategy. groundfrom largercarnivores (Herrero 1978). During The subtropicalsloth bear is also an expertclimber but the Pleistocene, there was an abundanceof large terres- thecubs remainon the groundwhen the female is in a tree. trialpredators in the opencountry, including the cursorial If threatened,the female leaves the tree immediatelyand giant short-facedbear (Arctodussimus), one of the most flees on the ground,her cubs sometimesdeparting ahead powerful terrestrial mammalian predators to evolve of her (Laurieand Seidensticker 1977). They attribute anywhere (Kurten 1967, Kurten and Anderson 1980). this behaviorto the presenceof the leopard,a significant With the passing of the giant short-facedbear during the arboreal predator, which sometimes kills sloth bears Pleistocene extinctions, its open country habitat was (Kurtand Jayasuriya1968). Consequently,climbing a EVOLUTIONOF BEARS * Stirling and Derocher 197 tree is ineffective for escape and might make the bear spread, genus that first evolved in Europe during the more vulnerableto predation. They also note that large Miocene but duringthe Pliocene spreadto North Amer- ungulatesare more likely to standand fight predators,or ica, Asia, and Africa (Hendey 1977). They were appar- attackthem, than run away. They suggest the presenceof ently extinct by the end of the Pliocene. It is possible, elephants (Elaphus maximus) and rhinoceros(Rhinoc- though unknown, that in the northernhemisphere they eros unicornis), which are capable of pulling down or were out competedby other species of bears. However, pushing over even medium-sized trees, furtherreduce the present day lack of ursid successors in central or their value as escape habitatfor sloth bears. Despite its southernAfrica is puzzling, considering the large and small size, the sloth bear is known to attackhumans if variable food base, unless the rapid evolution of other surprisedand is regardedas dangerousby local people carnivoresand primates(including humans)into avail- (Laurieand Seidensticker 1977). Like the much larger able niches excluded them after the passing of the brownbears, aggressive behaviormay be a consequence Langebaanwegbear. of not being able to rely on trees for escape. It is likely that interspecific,and possibly intraspeci- Interspecificcompetition from mammals other than fic, predationinfluenced the behaviorof temperatebears bears may have played a significant role in preventing duringwinter denning. Bearsdiffer from otherhibernat- bears from invading some areas. Alternatively,an ab- ing mammalsin thattheir body temperaturedrops only a sence of competitors for a particularniche may have few degreesand they arecapable of rapidarousal (Folk et facilitated evolution and dispersal. For example, the al. 1972). This may be necessarybecause females give sloth bear apparentlywas able to enter the myrmecoph- birth to altricialyoung and probablyhave to give them agic niche in southern Asia because areas of suitable continuousattention to ensuretheir survival. However, habitatwere unoccupiedby the 3 other allopatricmam- from the numberof reportsin the literatureon the killing malianmyrmecophages present (Laurie and Seidensticker of bearsin theirdens by otherpredators, including ursids 1977). In South America,there are 5 sympatricspecies (e.g., Paquetand Carbyn 1986, Ross et al. 1988), it is clear of myrmecophages,which appearto occupy all available thatbears in dens must also be able to arousethemselves habitat,and there are no bears that eat ants or termites quickly,if necessary,to protectthemselves and their cubs (Laurieand Seidensticker1977). However,in temperate from being killed. North America and northernAsia, where there are no mammalianmyrmecophages, ants may form a signifi- cant partof the diet of blackand brown bears (e.g., Hatler INDIVIDUALVARIATION 1972, Vereschagin 1976). In general, biologists who have worked with bears Pruitt and Burghardt(1977) note that the mountain have been impressedwith how variablethe behaviorof gorilla (Gorilla gorilla beringei) appears to occupy a individualsappears to be. Similarly,most of us have the similar niche in central Africa to that occupied by the distinct,if unquantifiedimpression that bears remember blackbear in NorthAmerica. Similarly,there are numer- a greatdeal aboutparticular areas and how to do things. ous species of primatesin northernSouth America and The success that circuses have had with trainingbears other tropicalregions. What role, if any, primatesmay also suggests they are good at learningnew tasks. Yet, have had on distributionpatterns of the moder bears is with the exceptionof a very few quantitativestudies such unknown. as Bacon and Burghardt(1976a, b), there is little more Althoughthere are no bearsin southernAfrica today, than an anecdotalappreciation in the literatureof their bears of the genus Agriotheriumhave been found in ability to learn or remember things. As long-lived Pliocene deposits dating back between 4 and 5 million mammals that spend most of their lives within a home years (Hendey 1977). The Langebaanwegbear is the range and show strong seasonal fidelity to particular largestterrestrial predator recorded from southernAfrica locations, bears probably learn much about the area, and,from its largejaws andthe degreeof developmentof includingwhere and how to find food or othernecessities its incisors and canines, appearsto have evolved into a undera variety of circumstances. The variabilityin the largelycarnivorous niche. Itsmuzzle was shortand broad ways bears from the same populationbehave within a and the palate was even shorterthan that of the short- particulararea may be influencedby bothgenetic factors faced bearsof NorthAmerica. The sagittalcrest was high and learning. If there is a lot of variabilitywithin the and the zygomatic archwas wide, which are also indica- habitat(e.g., in food types and availability,cover, and tive of strong musculatureindicative of a carnivore. topography),over time therewill be differencesin some ApparentlyAgriotherium was a short-lived, but wide- of the experiences individualbears have while feeding. 198 BEARS-THEIR BIOLOGY AND MANAGEMENT

Thus,through learning, some bearsmay develop individ- than those of brown bears but we do not know if that ual differencesin food preferences,vary in the degree to accountsfor a lackof comparablevariability in the skulls. which they prey on live animals, or respond to distur- bances. Individualswill develop behavioralpatterns that are molded by their own experiences. Similarly, some SOCIAL ORGANIZATION behaviorswill be learnedby cubs while accompanying In general, the presentday bears tend to live most of their mothers during the long period before weaning. their lives as solitary individuals, with social groups However, there has been no attemptin the literatureto being limitedto females with cubs andmale-female pairs review or quantifythe aspects of learningnoted above. duringthe breedingseason. There is no indicationfrom An unexploredbut possibly fertile areafor investiga- the fossil recordthat the ancestorsof the modernbears tion is thatof individualvariation in niche exploitationby were any more gregarious(Kurten 1976). As with other different individuals within a populationas a result of species, their social organizationappears to have been variations in their morphology. In a recent review, influencedby the risk of predation,intraspecific compe- Lomnicki(1988) arguedfor the adaptivesignificance of tition, and the distributionof resources(Wrangham and individual variation within populations. Similarly, Rubenstein1986). Wallace (1982) suggestedthat the higherdegree of phe- It is possible that some of the ancestralursids might notypic variationthat sometimes occurs among the off- have been vulnerableto significantpredation because of spring from the same parents, compared to those of their small size. However, it appearsthat as body size, unrelatedanimals, could be adaptivebecause, in the case teeth, and claws increasedin size throughthe Pliocene of a shortageof resources,the survivalof at least some of and Pleistocene epochs, bears were probably not as the progeny may be possible. Kurten and Anderson vulnerable to predationfrom non-ursids. As a result, (1980) noted that Erdbrink(1953) listed 232 recent and therewas probablylittle significantpressure to aggregate 39 fossil species and subspecies of brown bears in what for the purposeof groupdefence or vigilance. We suspect they describeas "... a waste of taxonomiceffort which ... that, similarto the moder bears,the threatof predation is unparalleled". Ignoring the unrealistic amount of by other species of bears, or males of theirown species, taxonomic splittingthat was done, the fact remainsthat might have had a significantinfluence on theirbehavior thereis substantialmorphological variation in the skulls andecology. The smallerbears might have used treesas of these mammals.This was broughthome to us recently escape habitatwhile largerspecies could standand fight when we examined a small sample of skulls from male if necessary. brown bears collected from the southern Caucasus Intraspecificcompetition, including predation by large Mountainsin the U.S.S.R. In broad terms, the shapes males, has been suggestedto be importantin population variedfrom what we thinkof as normalfor a brownbear regulation of North American black and brown bears to one with a shortenedface and high foreheadreminis- (e.g., Kemp 1972, Stringham1983). The importanceof is unknown. cent of a pandato anotherthat was elongatedrather like this factor to other species Intraspecific a wolf skull. A similaramount of variationwas reported predationalso occurs in polar bears (Tayloret al. 1985) and illustratedfor brownbears in Hokkaidoby Kadosaki but in the open habitatof the arcticsea ice it may be less and et al. (1989:27, Fig. 2). The consequences of such importantthan in the forest (Ramsay Stirling 1986). and are able to outrunadult males variationin phenotypicexpression on the developmentof Cubs develop rapidly are 6 months old. 1 different feeding strategies by individual bears is un- by the time they Nevertheless, the known. Possibly the variabilityin skull morphologyis consequenceof intraspecificcompetition, including threatof is differentialdistribution of bears greaterin a species like the brownbear because its habitat predation, by female bears and the food resources are highly variable. Does this age and sex class. Forexample, adult polar and allow differentindividuals within a populationto special- with cubs on the sea ice duringthe breedingseason, on land in Hudson the season, ize in particularsubniches? The retentionof such vari- Bay during non-breeding tend to themselves from habitatswhere adult ability in skull morphology in brown bears from fossil segregate males are most abundant et al. 1977, throughrecent species (Erdbrink1953) suggests there (Stirling Ramsay and Derocherand 1990a). may be some benefit we do not understand.In compari- Stirling 1986, Stirling Home of for whichdata are available, are son, based upon a superficialcomparison of polar bear ranges bears, and have a of skulls, the same amountof obvious variabilitywas not extremely variable(Table 2) high degree with In most cases, this presenteither within populationsor between them. The overlap conspecifics. probably resources are distributedand not diet and habitatof polarbears are probablyless variable indicates that widely EVOLUTIONOF BEARS * Stirling and Derocher 199

defendable. Group defence of a home range would membersof the group can be fed within their territory. probablynot be any moreenergetically beneficial since it Exceptfor briefperiods in special circumstances,such as is unlikely the defendablearea would increaseenough to at salmon streams,bears cannot do this because the prey supporta group of bears. availableto them are distributedat densities lower than Intraspecificcompetition for patchy and ephemeral those in lion habitat.For brown bears, killing an ungulate resources,and the evolution of a largely vegetariandiet, is a rareenough event thatit may be advantageousnot to which necessitatesa large food intakebecause of a non- share it. Additionally,in temperateregions, the cooler ruminantdigestive tract,likely acted against the forma- climate may act to preserve a carcass, making it more tion of large social groups of bears. Groups of bears beneficialfor an animalto guardit forcontinued use. The would be likely to exhaust food patches more quickly warmerclimate in lion habitat,plus the abundanceof than individuals so they would have to move more scavengers,may makeit advantageousto sharea kill and frequentlyin searchof new feeding areas. The effect of ensure consumption by kin. Although brown bears, additionaltravel could be negativebecause the large size especially subadults,are occasionally cursorialhunters and massive build of bearsappears to reducetheir ener- of mammals as large as elk or caribou (Cole 1972, getic efficiency of movement(Hurst et al. 1982). If there Reynoldsand Gamer 1987), and may huntin pairs(Cole is a similartrend in otherspecies of bears,it is likely that 1972, M. Meagherpers. commun.), the rateat which they intraspecificcompetition would negate feeding in groups are able to kill does not approachthat of lions. If bears except in exceptionalcircumstances where there is a high huntedin sleuths, they would have to travelextensively density of high quality food, such as at a salmon stream between kills, as do packs of wolves, because of the low or a garbagedump. density of prey species. Each bear would receive a In consideringwhy bearsare not found in sleuths,it is reducedcaloric return from each kill because of the need insightfulto comparetheir social organizationto thatof to share. However, comparedto wolves, long distance lions. Bearsand lions bothgive birthto altricialoffspring travelby bearsis slow andlikely muchmore costly in the so that substantialpostpartum care is required. In lions, energeticsense, so thatsolitary hunting is the best overall the mother-offspringbond is the basis of groupformation strategy. (Packer 1986). Also like bears, the ancestors of lions While feeding on a vegetarian or omnivorous diet, were solitary carnivores, as most other felids still are individualbears are capable of sustainingand protecting today (Packer1986). Most studiesattribute group living both themselves and their cubs in most circumstances in lions to the benefits associatedwith the advantagesof without the assistance of conspecifics. Consequently, but killing large prey, Packer (1986) arguedthat group there is little apparentnutritional benefit in becoming in living lions appearsto have evolved despite possible more socially developed. Even in the completely car- of disadvantages grouphunting. The kin-basedstructure nivorous polar bears, the small size of their majorprey of female pridesresults from natal area philopatry (Packer item, ringedseals, probablynegates any potentialadvan- and the 1986) may represent rudimentarymechanism tage from huntingas a group or sharinga kill with any from which levels of higher sociality develop. A major conspecific except offspring. Like brownbears hunting advantageof group living in lions may be protectionof ungulates, the rate at which polar bears are able to kill the cubs from infanticidalmales, resulting in increased large prey such as beardedseals or odontocete whales success reproductive thatnegates possible disadvantages does not appearto be frequentenough to stimulatethe of Packeret group hunting(Packer 1986, al. 1988). development of group hunting. Nevertheless, large Both infanticideand natal areaphilopatry are closely numbersof polar bears will scavenge togetherat whale in ursid all ursids paralleled ecology, yet remainsolitary. carcasses or dumps, as do brown or black bears, though However,there are 2 importantdifferences. Femalelions in those circumstanceseach animal still behaves inde- can come into oestrus at any time of year comparedto pendently. which are seasonal breeders. bears, Thus, a male lion Lastly,in contrastto lions, manypast and present ursid be able to mate with a lioness if he may kills her cubs, species hibernateand this may restrictthe development of the regardless season, somethingunlikely with bears. of sociality. By way of analogy, there is a fairly wide infanticideis a less Consequently, importantstimulus for rangein the developmentof sociality in groundsquirrels. in bearsthan in lions. We groupliving suggest food size Apparentlywhat characterizesthe most social species is and density may constitute the critical difference. By a prolonged association between adults and subadults lions are able to obtain hunting together, large enough that can only occur with short, or absent, periods of units of often that all high quality food, enough, the hibernation(Armitage 1981). Even though some pres- 200 BEARS-THEIR BIOLOGY AND MANAGEMENT

ent-daybears may not hibernatein warmerregions, their It is also possible that the apparentlysolitary forest- herbivorousdiet in a forest environmentdoes not lend dwelling bears are more social than previouslythought. itself to the developmentof sociality as discussedabove. Reassociationof family groups after breakuphas been In contrast to the varied diet of omnivores such as reported(Reynolds and Beecham 1980, Garshelis and blackbears, more than 99% of the diet of the giant panda Pelton 1981). In black bears, female offspring tend to consists of stems, branches,and leaves of only 2 bamboo settle in or adjacentto the home ranges of theirmothers species (Schalleret al. 1985). Thereis seasonalvariation (Rogers1987a) while malecubs disperse. Rogers (1987b) in the use of each species and the partsof the plants that also suggested that female black bears can recognize are eaten but, since bamboo grows year-roundat high independentoffspring and behave in a bereficial manner density, pandascan normallyobtain all their metabolic dictatedby genetic relatedness. requirementswithin much smallerareas than other spe- cies of bears (Table 2). This is probablystrongly influ- enced by the additional fact that there is no seasonal COMMUNICATION variationin bambooquality (Schaller et al. 1985). Thus, Because bears are solitary animals and are usually there is no need for the panda to either change diet or difficultto observe, theirmethods of communicationare hibernate. Even so, they show little social organization. not well understood.The degree to which bearsvocalize Probablybecause of their solitary existence, female varies between species. Herrero(1978) suggested that bears appearto be induced ovulators(Bunnell and Tait blackbears are more vocal thanbrown bears because they 1981). There is little advantageto ovulating spontane- are more of a forest animaland have restrictedvisibility. ously if the chance is good there would not be a male Otherforest species such as spectacledbears, sloth bears, nearbyat the time. Fromobservations in zoos and in the and sun bears also seem to be quite vocal (Laurie and field (Meyer-Holtzapfel 1957, Horocker 1962, Spar- Seidensticker1977, Peyton 1980, Bunnell 1987). Pandas rowe 1968, Herreroand Hamer 1977), it appears that in zoos vocalize during oestrus (Kleiman et al. 1979) male and female pairs may remaintogether for up to 2 while those in the wild have a repertoireof approximately weeks. Males may try to sequesterfemales to isolated 11 identifiablesounds (Schaller et al. 1985). In contrast, areas where they are less likely to encountercompeting in ourexperience, polar bears vocalize little. Femalesand males (Herreroand Hamer 1977, Ramsay and Stirling cubs may call to each otherif they become separated,or 1986) and copulation usually occurs many times. In- if the female is leaving a site andwants the cub to follow. trasexualcompetition between males for mating privi- Males snort and chuff (Wemmer et al. 1976) during leges can be intense and some females may mate with intrasexualagonistic behavior but otherwise they lackthe more than 1 male (Sparrowe1968). Since female bears distinctivecalls that characterizeother carnivores. mayhave multiple ovulations (Ramsay and Stirling 1986), Several species of bears marktrees. The functionof but it is possible for members of the same litter to have this behaviorhas not been confirmedexperimentally differentfathers (Bunnell and Tait 1981). For example, the information conveyed likely includes territorial Hornocker(1962) observed a female brown bear that markingand possibly the statusof the individuals. mated 10 times with 4 males in 2 hours. How frequent The use of scents, including pheromones,have not in are polyandrousmating is, andwhat effect it may have hadon been documented bearsthough they likely present. the evolution of the social organizationof bears is un- For example, we have trackedindividual adult males on known. the sea ice duringthe breeding season in the spring,when bears. Nevertheless, some sociality does exist although its theirpaths may cross the tracksof dozens of other until a male crosses the function may not necessarily be fully understood. For There is no discernibleresponse a lone adultfemale. is instantand he example, during the ice-free period in western Hudson pathof Recognition the track until he catches to her or is Bay, 2 to 14 or more adultmales may aggregateclosely then follows up not know how a and show extremetolerance of conspecifics (Kolenosky distractedby anotherfemale. We do the track of a and 1987, Derocher and Stirling 1990b). In this circum- male polar bear recognizes lone, but it is clear that he stance, considerable ritualized fighting may also take presumablyoestrus, adult female can. It seems a chemical stimulusis involved. place in which combatantsare not injured(Latour 1981). likely of color in bears is Two adultfemale polar bears, each with cubs, were ob- In general, the presence patterns when to some served interactingnon-aggressively, and even attending fairly conservative,especially compared each other's cubs on occasion, over a period of 6 weeks othercarnivores (Nowak andParadiso 1983). However, on the commu- while feeding togetherat a garbagedump (Lunn 1986). contrastingcolor patterns body may help EVOLUTIONOF BEARS * Stirling and Derocher 201 nicatean animal'spresence, especially in a foresthabitat. may have had on the evolution of the moder bearsbut it The existence of color patternsand contrastis greatestin has probablyinfluenced aspects of theirleaned behavior lower latitude species such as the spectacled bears and such as movementpatterns and diet preferences. As the pandasin particular,but also to a lesser degreein the sloth habitat available for bears continues to decrease, we bear. Sun bears, Asiatic black bears, spectacled bears, reducethe genetic variabilitythat remains available to the and usually Americanblack bears,have a patchof white species. This may alter the patternof naturalselection on the chest. The muzzle of these smaller forest bears, because genetic drift increases in smaller populations andeven partof the face of the sun bear,are much lighter (Allendorf 1983). in color than the rest of the head or upper body (see Largecarnivores are sensitive indicators of ecosystem Nowak and Paradiso1983, Bunnell 1987). By compari- health and could be used to define the minimum area son, there is less contrastin the body color patternsof necessaryto preserveintact ecosystems (Eisenberg 1980). brown bears. In the polar bear, which lives in the most However, it is estimatedthat areas in excess of 106km2 open habitatof any species of bear,there is no contrastin are requiredfor mammals 50 kg and larger to persist body color at all, with the exceptionof the blacknose and throughevolutionary time (i.e., 105 to 106 years) (Be- eyes. Schalleret al. (1985) suggestedthe complex body lovsky 1987). This estimate assumes a scenario of no markingsof the pandasent importantsignals to conspeci- majorclimatic change. It is clear that bears will never fics and Ewer (1973) thoughtthat the chest markingsin regain the vast expanses in which they evolved, so it is bearspossibly servedto accentuatea threatposture when vital for us to ensurethat the remainingpopulations have an animalstood on its hind legs. Bears in generaltend to large enough areasof appropriatehabitat. Yet, it is also approachconspecifics in a head-onmanner so that con- apparentfrom the size of the home rangesof most species centrationof the markingpatterns in the chest and facial of bears (Table 2) and the minimum population sizes areas would enhance identificationand communication. requiredto maintainan adequategenetic pool that large Head and neck orientation,ear position, and the orienta- geographicareas will be requiredif bearsare to survive. tion of the mouth and teeth are probablyall important Solution of this dilemma will requirecreative thinking. though they have been little studied. Somehow, we will need to delineate and manage large Tails in the ursidsare conspicuous by theirsmall size. areasof the most optimalremaining wild and semi-wild In many carnivorespecies, tails serve an importantfunc- habitatfor a varietyof equallyimportant priorities, one of tion in communicationand in many instancesare highly which is the conservationof large carnivores,including patterned(Ewer 1973). Even in otherspecies with short bears. tails such as the lynx (Lynxcanadensis), the tail is held and is used in social contact and upright maintaining LITERATURECITED communication(Ewer 1973). The absence of a func- ALLENDORF,F.W. 1983. Isolation,gene flow, and tional tail have been influenced the genetic may by relatively differentiationamong populations. Pages 51-65 in C.M. non-social natureof the bears and the fact that the most Schonewald-Cox,S.M. Chambers, B. MacBryde,and L. importantdisplays seem to involve frontal and bipedal Thomas,eds. Geneticsand conservation: a reference for display. managingwild animal and plant populations. Benjamin/ Cummings,London. 722pp. ALT, G.L., G.J. MATULA,JR., F.W. ALT, AND J.S. LINDZEY. 1980. Dynamicsof home andmovements of adult MANAGEMENTIMPLICATIONS range blackbears in northeasternPennsylvania. Int. Conf. Bear It is not possible to predictthe directionin whichbears Res.and Manage. 4:131-136. may evolve but it is obvious from the generationtime AMSTRUP,S.C. 1986. Researchon polarbears in Alaska, 1983- 1985. in involved thatchange will be slow. Largespecies evolve Pages85-108 Polarbears: Proc. ninth working meetingof IUCN/SSCPolar more slowly because of low rates of reproductionand SpecialistGroup. IUCN, Cambridge.152pp. rates of extinction This not high (Stanley 1979). may , AND J. BEECHAM. 1976. Activity patternsof radio- bode well in a world which appearsto be changingever collaredblack bears in Idaho.J. Wildl.Manage. 40:340- more quickly, especially when, as Peters(1983:196) has 348. K.B. 1981. noted, "Evolutionhas favoredsmaller species, and large ARMITAGE, Socialityas a life-historytactic of 48:36-49. size tends to be an evolutionarydead end". groundsquirrels. Oecologia BACON, ANDG.M. BURGHARDT.1976a. All extant E.S., Ingestive behav- populations of bears have been hunted, iorsof theAmerican black bear. Int. Conf. Bear Res. and displacedfrom habitat, or impactedin some otherway by Manage. 3:13-25. the presenceof man. It is difficultto assess the effect this _ , AND . 1976b. Learningand color discrimination 202 BEARS-THEIR BIOLOGY AND MANAGEMENT

in the American black bear. Int. Conf. Bear Res. and EWER,R.F. 1973. The carnivores.Cornell Univ. Press,Ithaca, Manage. 3:27-36. N.Y. 494pp. BELOVSKY,G.E. 1987. Extinction models and mammalian FOLK,G.E., JR., M.A. FOLK,AND J.J. MINOR.1972. Physiologi- persistence. Pages 35-57 in M.E. Soule, ed. Viable cal conditionof three species of bearsin winterdens. Int. populations for conservation. CambridgeUniv. Press, Conf. Bear Res. and Manage. 2:107-124. Cambridge. 189pp. FRANZMANN,A.W., C.C. SCHWARTZ,AND R.O. PETERSON. BOERTJE,R.D., W.C. GASAWAY,D.V. GRANGAARD,AND D.G. 1980. Moose calf mortality in summer on the Kenai KELLEYHOUSE.1988. Predation on moose and caribou by Peninsula,Alaska. J. Wildl. Manage. 44:765-768. radio-collaredgrizzly bearsin east centralAlaska. Can.J. GARSHELIS,D.L., AND M.R. PELTON. 1981. Movements of Zool. 66:2492-2499. black bearsin the GreatSmoky MountainsNational Park. BUNNELL,F.L. 1987. Small bears. Pages 96-97 in D. J. Wildl. Manage. 45:912-925. MacDonald,ed. The encyclopediaof mammals.Equinox, GEIST,V. 1978. Life strategies, human evolution, environ- Oxford. 928pp. mentaldesign: toward a biologicaltheory of health. Sprin- , ANDD.E.N. TAIT. 1981. Population dynamics of bears ger Verlag, New York, N.Y. 495pp. - implications. Pages 75-98 in C.W. Fowler and T.D. . 1987. On speciation in Ice Age mammals, with special Smith, eds. The dynamicsof large mammalpopulations. referenceto cervids and caprids. Can. J. Zool. 65:1067- John Wiley and Sons, New York, N.Y. 477pp. 1084. , AND T. HAMILTON.1983. Forage digestibility and GITTLEMAN,J.L. 1985. Carnivorebody size: ecological and fitness in grizzly bears. Int. Conf. BearRes. and Manage. taxonomiccorrelates. Oecologia 67:540-554. 5:179-185. GUTHRIE, R.D. 1984. Mosaics, allochemicals and nutrients. CALEF,G.W., ANDJ. VAN CAMP.1987. Population dynamics Pages 259-298 in P.S. Martinand R.G. Klein, eds. Qua- of bison. Pages 21-24 in H.W. Reynolds and A.W.L. ternaryextinctions: a prehistoricrevolution. Univ. Ari- Hawley, eds. Bison ecology in relationto agriculturalde- zona Press, Tuscon. 892pp. velopmentin the Slave Riverlowlands, NWT. Can.Wildl. HARINGTON,C.R., A.H. MACPHERSON,AND J.P. KELSALL. Serv. Occas. Pap. 63. 72pp. 1962. The barren-groundgrizzly bearin northernCanada. CHASSIN,P.S., C.R. TAYLOR,N.C. HEGLUND,AND H.J. SEEHER- Arctic 15:294-298. MAN. 1976. Locomotion in lions: energetic cost and HATLER,D.F. 1972. Food habits of black bears in interior maximumaerobic capacity. Phys. Zool. 49:1-10. Alaska. Can. Field Nat. 86:17-31. COLE,G.F. 1972. Grizzly bear-elk relationshipsin Yellow- HAZUMI,T., ANDN. MARUYAMA.1986. Movements and home stone NationalPark. J. Wildl. Manage. 36:556-561. ranges of Japanesebears in Nikko. Int. Conf. Bear Res. CLUTrON-BROCK, T.H., ANDP.H. HARVEY. 1978. Mammals, and Manage. 6:99-101. resources and reproductivestrategies. Nature 273:191- HELLGREN,E.C., ANDM.R. VAUGHAN.1987. Home range and 195. movements of winter-active black bears in the Great , AND _ . 1983. The functional significance of Dismal Swamp. Int.Conf. BearRes. andManage. 7:227- variationin body size amongmammals. Pages 532-563 in 234. J.F. Eisenbergand D.G. Kleiman, eds. Advances in the HENDEY,Q.B. 1977. Fossil bearfrom SouthAfrica. S. African study of mammalianbehavior. Spec. Publ. Am. Soc. J. Sci. 73:112-116. Mammal. Lawrence,Kans. 753pp. HERRERO,S.M. 1978. A comparisonof some featuresof the ___ , ___ , ANDB. RUDDER. 1977. Sexual dimorphism, evolution, ecology, and behavior of black and grizzly/ socionomic sex ratioand body weight in primates.Nature brownbears. Carnivore 1:7-17. 269:797-800. , AND D. HAMER. 1977. Courtship and copulation of a DEAN, F.C., L.M. DARLING,AND A.G. LIERHAUS. 1986. pair of grizzly bears, with comments on reproductive Observationsof intraspecifickilling by brownbears, Ursus plasticity and strategy. J. Mammal. 58:441-444. arctos. Can. Field. Nat. 100:208-211. HORNOCKER,M.G. 1962. Populationcharacteristics and social DEMASTER, D.P., AND I. STIRLING.1981. Ursus maritimus. and reproductivebehavior of the grizzly bear in Yellow- Mammal.Species 145:1-7. stone National Park. M.S. Thesis, Mont. State Univ., DEROCHER,A.E., ANDI. STIRLING.1990a. Distribution of polar Bozeman. 94pp. bears (Ursus maritimus) during the ice-free period in HURST,R.J., M.L. LEONARD,P.D. WATTS,P. BECKERTON,AND western Hudson Bay. Can. J. Zool. 68:In press. N.A. 0RITSLAND. 1982. Polar bear locomotion: body ,_ AND . 1990b. Aggregating behaviour of adult temperatureand energeticcost. Can. J. Zool. 60:40-44. male polar bears (Ursus maritimus). Can. J. Zool. 68:In INTERAGENCYGRIZZLY BEAR COMMITTEE. 1987. Grizzly bear D.C. press. compendium.Natl. Wildl. Fed.,Washington, 540pp. JINCHU. 1988. Re- EARLE, M. 1987. A flexible body mass in social carnivores. JOHNSON,K.G., G.B. SCHALLER,AND H. Am. Nat. 129:755-760. sponses of giantpandas to a bamboodie-off. Natl. Geogr. EISENBERG,J.F. 1980. The density and biomass of tropical Res. 4:161-177. in the mammals. Pages 35-56 in M.E. Soule and B.A. Wilcox, JONKEL, C., AND I.M. COWAN. 1971. The black bear eds. Conservationbiology: an evolutionary-ecological spruce-firforest. Wildl. Monogr.27. 57pp. of black bears perspective.Sinuaer Associates, Sunderland, Mass. 395pp. , ANDF.L. MILLER.1970. Recent records ERDBRINK,D.P. 1953. A review of fossil and recent bears of (Ursus americanus)on the barrengrounds of Canada. J. the Old World. 2 Vols. Deventer,Drukkerij Jan de Lange. Mammal. 51:826-828. 597pp. KADOSAKI, M., A. KAWAHARA, J. IIZUKA, AND H. FUJIOKA. EVOLUTIONOF BEARS * Stirling and Derocher 203

1986. Comparativemorphological studies of the skulls Wildl. Manage. 41:413-425. andteeth of the brownand black bears of Japan:(I) crowns LOMNICKI,A. 1988. Populationecology of individuals. Prin- of canines and molars. Annu. Rep. Hist. Mus. Hokkaido ceton Univ. Press, Princeton,N.J. 223pp. 14:31-44. L0N0,0. 1970. The polarbear (Ursus maritimus Phipps) in the ___, ___, ___,AND . 1989. Comparative morpho- Svalbard area. Norsk PolarinstituttSkrifter Nr. 149. logical studies of the skulls and teeth of the brown and 103pp. black bears of Japan:(IV) skulls (1). Annu. Rep. Hist. LOWRY,L.F., J.J. BURNS,AND R.R. NELSON.1987. Polar bear, Mus. Hokkaido 17:13-43. Ursus maritimus,predation on belugas, Delphinapterus KELLY,B. P. 1988. Beardedseal. Pages 77-94 in J.W. Lentfer, leucas, in the Bering and Chukchiseas. Can. Field Nat. ed. Selectedmarine mammals of Alaska:species accounts 101:141-146. with researchand management recommendations. Marine LUNN,N.J. 1986. Observationsof nonaggressive behavior MammalCommission, Washington, D.C. 275pp. betweenpolar bear family groups. Can.J. Zool. 64:2035- KEMP,G.A. 1972. The dynamicsand regulationof black bear 2037. (Ursus americanus)populations in northernAlberta. Int. , ANDI. STIRLING.1985. The significance of supplemen- Conf. Bear Res. and Manage. 2:191-198. tal food to polarbears during the ice-freeperiod of Hudson KILIAAN, H.P.L., AND I. STIRLING. 1978. Observations on Bay. Can. J. Zool. 63:2291-2297. overwintering walruses in the eastern Canadian High MANVILLE,A.M. 1983. Human impact on the black bear in Arctic. J. Mammal. 59:197-200. Michigan's Lower Peninsula. Int. Conf. Bear Res. and KLEIMAN,D.G., W.B. KARESH, AND P.R. CHU. 1979. Behavio- Manage. 5:20-33. ral changes associated with oestrus in the giant panda MATHEWS,N.E., ANDW.F. PORTER.1988. Black bear preda- (Ailuropoda melanoleuca) with comments on female tion of white-taileddeer neonates in the central Adiron- proceptivebehaviour. Int. Zoo Yearb. 19:19-21. dacks. Can. J. Zool. 66:1241-1242. KOLENOSKY,G.B. 1987. Polar bear. Pages 474-485 in M. MEAGHER,M. 1973. The bison of Yellowstone NationalPark. Novak, J.A. Baker, M.E. Obbard,and B. Malloch, eds. U.S. Natl. ParkServ. Sci. Monogr. Ser. No. 1. 161pp. Wild furbearermanagement and conservation in North MEYER-HOLTZAPFEL, M. 1957. Das verhalten der baren. America. Ashton-PotterLtd., Concord,Ont. 1150pp. Handb.Zool., Band 8, Teil 10:1-28. KRUUK,H. 1972. The spotted hyena. Univ. Chicago Press, MILLER,F.L., A. GUNN, ANDE. BROUGHTON.1985. Surplus Chicago. 335pp. killing as exemplified by wolf predation on newborn KURT,F., ANDA.G. JAYASURIYA.1968. Notes on a dead bear. calves. Can. J. Zool. 63:295-300. Loris 11:182-183. MILLER,S.D. 1985. An observationof inter-and intra-specific KURTEN,B. 1963. Fossil bears from Texas. The Pearce- aggressioninvolving brown bear, black bear, and moose in SellardsSeries, Texas MemorialMus. (Univ. Texas) 1:1- southcentralAlaska. J. Mammal. 66:805-806. 15. MURIE, A. 1981. The grizzlies of MountMcKinley. U.S. Natl. ___ . 1966. The Pleistocenebears of NorthAmerica, I: Genus ParkServ. Monogr. Ser. No. 14. 251pp. Tremarctos,spectacled bears. Acta Zool. Fenn. 115:1- MYSTERUD,I. 1973. Behaviour of the brown bear (Ursus 120. arctos) at moose kills. Norw. J. Zool. 21:267-272. 1967. The Pleistocene bears of North America, II: _. 1975. Sheepkilling andfeeding behaviourof the brown Genus Arctodus, short-faced bears. Acta Zool. Fenn. bear (Ursus arctos) in Trysil, southNorway 1973. Norw. 117:1-60. J.Zool. 23:243-260. _ 1968. Pleistocene mammalsof Europe. Weidenfeld NOWAK,R.M., ANDJ.L. PARADISO.1983. Walker's mammals and Nicholson, London. 317pp. of the world. Fourth ed. Johns Hopkins Univ. Press, ___ . 1976. The cave bearstory. ColumbiaUniv. Press,New Baltimore,Md. 1377pp. York,N.Y. 163pp. OZOGA,J.J., ANDL.J. VERME.1982. Predationby black bears , AND E. ANDERSON. 1980. Pleistocene mammals of on newbornwhite-tailed deer. J. Mammal. 63:695-696. NorthAmerica. ColumbiaUniv. Press, New York, N.Y. PACKER,C. 1986. The ecology of socialityin felids. Pages429- 442pp. 451 in D.I. Rubensteinand R.W. Wrangham,eds. Eco- LATOUR,P.B. 1981. Interactionsbetween free-ranging,adult logical aspects of social evolution: birds and mammals. male polarbears (Ursus maritimusPhipps): a case of adult PrincetonUniv. Press, Princeton,N.J. 551pp. social play. Can. J. Zool. 59:1775-1783. , L. HERBST,A.E. PUSEY,J.D. BYGOTr,J.P. HANBY,S.J. LAURIE, A., AND J. SEIDENSTICKER.1977. Behavioural ecology CAIRNS, AND M.B. MULDER.1988. Reproductive success of the sloth bear(Melanursus ursinus). J. Zool. (London) of lions. Pages 363-383 in T.H. Clutton-Brock,ed. Repro- 182:187-204. ductivesuccess: studies of individualvariation in contrast- LECOUNT,A.L. 1980. Some aspects of black bear ecology in ing breeding systems. Univ. Chicago Press, Chicago. the Arizonachaparral. Int. Conf. Bear Res. and Manage. 538pp. 4:175-179. PAQUET, P.C., AND L.N. CARBYN. 1986. Wolves, Canis lupus, _ . 1987. Causes of black bear mortality. Int. Conf. Bear killing denning black bears, Ursus americanus, in the Res. and Manage. 7:75-82. Riding Mountain National Park area. Can. Field Nat. LEKAGUL, B., AND J.A. MCNEELY. 1977. Mammalsof Thai- 100:371-372. land. Sahakarbhat, Bangkok. 758pp. PELCHAT, B.O., AND R.L. RUFF. 1986. Habitat and spatial LINDZEY, F.G., AND E.C. MESLOW. 1977. Home range and relationshipsof blackbears in borealmixedwood forest of habitatuse by blackbears in southwesternWashington. J. Alberta. Int. Conf. Bear Res. and Manage. 6:81-92. 204 BEARS-THEIR BIOLOGY AND MANAGEMENT

PETERS,R.H. 1983. The ecological implicationof body size. SMITH,T.G. 1980. Polar bear predationof ringed seals and CambridgeUniv. Press, Cambridge. 329pp. beardedseals in the land-fastsea ice habitat. Can.J. Zool. PEYTON,B. 1980. Ecology, distribution,and food habits of 58:2201-2209. spectacledbears, Tremarctosornatus, in Peru. J. Mam- , AND B. SJARE. 1990. Predation of odontocete whales mal. 61:639-652. by polar bears in nearshoreareas of the CanadianHigh PRUITT,C.H., ANDG.M. BURGHARDT.1977. Communication Arctic. Arctic 43:In press. in terrestrialcarnivores: Mustelidae, Procyonidae, and SPARROWE,R.C. 1968. Sexual behaviorof grizzly bears. Am. Ursidae. Pages 767-793 in T.A. Sebeok, ed. How animals Midl. Nat. 80:570-572. communicate.Indiana Univ. Press,Bloomington. 1128pp. STANLEY,S.M. 1979. Macroevolution:pattern and process. RALLS,K. 1976. Mammalsin which females are largerthan W.H. Freeman,San Francisco. 332pp. males. Q. Rev. Biol. 51:245-276. STEWART,R.R., E.H. KOWAL,R. BEAULIEU,AND T.W. ROCK. __ . 1977. Sexual dimorphism in mammals: avian models 1985. The impact of black bear removal on moose calf and unansweredquestions. Am. Nat. 111:917-938. survivalin east-centralSaskatchewan. Alces 21:403-418. RAMSAY,M.A., AND R.L. DUNBRACH. 1986. Physiological STIRLING,I. 1974. Midsummerobservations on the behaviorof constraintson life history phenomena:the example of wild polarbears (Ursusmaritimus). Can. J. Zool. 52:1191- small bear cubs at birth. Am. Nat. 127:735-743. 1198. , AND I. STIRLING. 1985. Interactions of wolves and polar , ANDW.R. ARCHIBALD.1977. Aspects of predation of bears in northernManitoba. J. Mammal. 65:693-694. seals by polarbears. J. Fish. Res. BoardCanada 34:1126- , AND . 1986. On the mating system of polar bears. 1129. Can. J. Zool. 64:2142-2151. , AND P.B. LATOUR. 1978. Comparative hunting abilities REYNOLDS,D.G., AND J.J. BEECHAM. 1980. Home range of polarbear cubs of differentages. Can.J. Zool. 56:1768- activities and reproductionof black bears in west-central 1772. Idaho. Int. Conf. Bear Res. and Manage. 4:181-190. , C. JONKEL, P. SMITH, R. ROBERTSON, AND D. CROSS. REYNOLDS,H.V., ANDG.W. GARNER.1987. Patterns of grizzly 1977. The ecology of the polar bear (Ursus maritimus) bear predationon caribouin northernAlaska. Int. Conf. along the westerncoast of HudsonBay. Can.Wildl. Serv. Bear Res. and Manage. 7:59-67. Occas. Pap. 33. 64pp. ROE,F.G. 1970. The NorthAmerican buffalo: a critical study STONOROV,D., ANDA.W. STOKES.1972. Social behavior of the of the species in its wild state. Second ed. Univ. Toronto Alaskan brown bear. Int. Conf. Bear Res. and Manage. Press, Toronto,Ont. 991pp. 2:232-242. ROGERS,L.L. 1987a. Effects of food supply and kinship on STORER,T.J., ANDL.P. TEVIS,JR. 1955. California grizzly. social behavior, movements, and population growth of PromontoryPress, New York, N.Y. 335pp. black bears in northeasternMinnesota. Wildl. Monogr. STRINGHAM,S.F. 1983. Roles of adult males in grizzly bear 97. 72pp. populationecology. Int. Conf. Bear Res. and Manage. . 1987b. Factors influencing the dispersal in the black 5:140-151. bear. Pages 75-84 in B.D. Chepko-Sadeand Z.T. Halpin, TAYLOR,M., T. LARSEN, AND R.E. SCHWEINSBURG.1985. eds. Mammaliandispersal patterns. The effects of social Observationsof intraspecificaggression and cannibalism structureon populationgenetics. Univ. Chicago Press, in polarbears (Ursus maritimus). Arctic 38:303-309. Chicago. 342pp. TRIVERS,R.L. 1972. Parentalinvestment and sexual selection. , ANDL.D. MECH.1981. Interactionsof wolves andblack Pages 136-179 in B. Campbell,ed. Sexual selection and bearsin northeasternMinnesota. J. Mammal.62:434-436. the descentof man, 1871-1971. Aldine, Chicago. 378pp. ROSENZWEIG,M.L. 1966. The strategy of body size in mam- VAN SOEST, P. 1982. Nutritionalecology of the ruminant. O malian carnivores. Am. Midl. Nat. 80:299-315. and B Books, Corvallis, Oreg. 374pp. Ross, P.I., G.E. HORNECK, AND B.L. HOREJSI. 1988. Late VERESCHAGIN,N.K. 1976. The brownbear in Eurasia,particu- denning black bears killed by grizzly bear. J. Mammal. larly the Soviet Union. Int. Conf. Bear Res. and Manage. 69:818-820. 3:327-335. SCHALLER,G.B. 1968. Food habits of the Himalayanblack VEZINA,A. F. 1985. Empiricalrelationships between predator bear(Selenarctos thibetanus) in the Dachigamsanctuary, and prey size among terrestrial vertebrate predators. Kashmir. J. Bombay Nat. Hist. Soc. 66:156-159. Oecologia 67:555-565. . 1972. The Serengeti lion: a study of predator-prey WALLACE,B. 1982. Phenotypic variation with respect to relations. Univ. Chicago Press, Chicago. 480pp. fitness:the basis for rank-orderselection. Biol. J. Linnean , H. JINCHU, P. WENSHI, AND Z. JING. 1985. The giant Soc. 17:269-274. pandasof Wolong. Univ. ChicagoPress, Chicago. 298pp. WEMMER,C., M. VON EBERS, AND K. SCAW. 1976. An analysis SELANDER,R.K. 1972. Sexual selection and dimorphismin of the chuffing vocalization of the polar bear. J. Zool. birds. Pages 180-230 in B. Campbell,ed. Sexual selection (London) 180:425-439. and the descent of man, 1871-1971. Aldine, Chicago. WRANGHAM, R.W., AND D.I. RUBENSTEIN. 1986. Social 378pp. evolution in birds and mammals. Pages 452-470 in D.I. SINCLAIR,A. 1975. The resourcelimitation of trophiclevels in Rubensteinand R.W. Wrangham,eds. Ecologicalaspects tropical grasslandecosystems. J. Anim. Ecol. 44:497- of social evolution. PrincetonUniv. Press,Princeton, N.J. 520. 551pp.