Some Aspects of Black Bear Ecology in the Arizona

SOME ASPECTS OF BLACKBEAR ECOLOGYIN THE ARIZONACHAPARRAL

ALBERT L. LeCOUNT, Arizona Game and Fish Department, 2222 West Greenway Road, Phoenix 85023

Abstract: A study of the black bear (Ursus americanus) on a 100-km2study area in the chaparralvegetation type of Arizona was initiatedin 1973. During the subsequent 3.5-year period, 44 individual bears were capturedand minimum density of 1 bear per 2 km2 was estimated. Twenty-eightbears were radio-instrumentedand more than 1,100 locations were recorded.The radio-locationsindicated that subadultmales have a home range averaging42 km2, adultmales 29 km2, adultfemales 18 km2, and subadultfemales 13 km2. There is considerableoverlap of home ranges among adult males. A lesser degree of overlap was observed for adult females. Twenty-fourdens were located. Most den sites were at elevations between 1,300 and 1,500 m. Some bears den by 1 November, the majorityby 15 November. Emergencefrom dens begins about 15 Marchand all bears, except females with cubs, leave theirdens by 15 April. Femaleswith cubs remainat den sites approximately30 days longer.

Until recently, Arizona black bears were of little interest to either hunters or wildlife biologists. The majorityof bears taken in the state were shot incidental to the hunting of other big game. Few sportsmen hunted specifically for bears. Campers and picnickers also encountered bears on occasion, and livestock operators suffered varying degrees of livestock loss each year from bears. As Arizona's population has increased, campers, picnickers, and summer home residents have increas- ingly encounteredbears. Also, more huntersbegan to pursue the black bear as an interesting and unique trophy in itself, ratherthan something to be shot incidental to other hunting. The increased interest and awarenessled to a statutorychange in classification for the bear in 1968, when the state legislaturechanged the status of bears from small game to big game. This change led to an increased emphasis on bear management in Arizona and pointed up the need for more information.This study is an attemptto fill some of the gaps in our knowledge of the ecology of black bears in Arizona. I am grateful to J. Wegge, J. deVos, V. Supplee, and K. Zahnter, Arizona Game and Fish Department, 1. area in the for their help in all phases of field work; to W. Carrel, Fig. Study Mazatzal Mountains of Arizona. laboratoryassistant, for laboratory,electronic, and ae- rial radiotrackingassistance; and to R. Smith, Game ranges from 1,200 to 2,300 m. Topographyis rocky Research and S. Supervisor, Gallizioli, Chief of Re- and steep with many slopes exceeding 50 percent. for their search, counsel, supervision, and editorial Annualprecipitation averages about 63 cm. Summer guidance. rains (July-September)are usually in the form of thun- derstorms. Winter STUDY AREA precipitation (December-March) normallycomes from major weatherfronts of 1-3 days This was study conducted in the vicinity of Four duration. Snow falls occasionally but seldom remains Peaks in the southern of the Mazatzal Moun- portion on the ground for more than a week. Midwinter dry tains in central Arizona on an area of approximately periods are not uncommon. Average temperatures 100 km2 (Fig. 1). Only one major road traverses the range from -5 C during midwinter to over 38 C in but an area, extensive trail network allows access by summer. Daytime temperaturesof 10-15 C are not un- horseback and foot. The elevation within the area common during the winter months. 176 BEARS - THEIR BIOLOGYAND MANAGEMENT

The primaryvegetative communityon the study area Each bear was tagged with a numberedmetal ear tag is InteriorChaparral (upper Sonoran life zone) (Brown in each ear, and a numberedplastic ear tag in one ear, and Lowe 1974). This type intergrades with the for subsequentidentification. Radio-transmittercollars Arizona Upland Desert Scrub (lower Sonoranzone) at were attached to 28 randomly selected bears. Sub- the lower elevations (approximately1,200 m) and with sequent radiotrackingwas done from the ground and some species such as ponderosapine (Pinusponderosa from aircraft,with over 1,100 radio-locationsrecorded. Laws.) and Gambel oak (Quercus gambelii Nutt.) of Twenty-two bears were radiotrackedto dens. Den- the Montane Coniferous Forest (transitionzone) at the ning dates were noted and the exact location of each highest portions of the study area. den was establishedin late December and January.In- The chaparralis a complex associationof shrubsand formation on each den and denning site was gathered low trees which, when well developed, create a cover the following spring after the bears' emergence. so dense as to be nearly impenetrable. Variations in soils, elevations, and exposure produce differences in RESULTS AND DISCUSSION species composition and dominance. One or 2 species often dominate the type locally to give it a specific Population Information character, but some 50 species of plants having From June 1973 to September 1976, 44 individual chaparral characteristics have been classified in the bears were captured and marked. In addition to the area. Manzanita (Arctostaphylos spp.), ceanothus animals captured, 2 cubs and 4 older unmarkedbears (Ceanothus spp.), mountain mahogany (Cercocarpus were known to occupy the study area, for a total of 50 spp.), garrya (Garrya spp.), and turbinella oak (Q. bears on approximately100 km2 (1 bear per 2.0 km2). turbinella Greene) are dominante and comprise a This total is considered to be a minimum population crown density of 50-90 percent. Trees such as Arizona estimate. Similar densities have been found in Alberta cypress (Cupressusglabra Sudw.), pinyon pine (Pinus (Kemp 1970), Montana(Jonkel and Cowan 1971), and edulis Engelm.), Emory oak (Q. emoryi Torr.), and Washington (Poelker and Hartwell 1973), and lower sugar sumac (Rhus ovata S. Wats.) make up 5-15 per- densities in Michigan (Ericksonand Petrides 1964) and cent of the cover. Major drainages contain riparian New York (McCaffrey et al. 1976). communitiescomposed of Arizonasycamore (Platanus Of the 22 adult bears captured, 55 percent were wrightii S. Wats.) and Fremont cottonwood (Populus males. However, the actual sex ratio might be closer to fremontii S. Wats.). the theoretical 1:1 because some bias undoubtedlyoc- Fruits produced by such chaparralspecies as ser- curred as a result of the selectivity of the capture viceberry (Amelanchier bakeri Greene), manzanita, technique. Males were more likely than females to en- chokecherry (Prunus serotina Ehrh.), pigeonberry countera trapbecause of their significantlylarger home (Rhamnuscalifornica Esch.), and the various species ranges. of oaks - as well as the prickly pear (Opuntiaspp.) in We observed little evidence of mortality during the the adjoiningdesert scrub type - provide an abundant course of the study. Natural mortality is certain to food supply for bears. occur but finding the evidence was extremely difficult The primaryeconomic land use of the chaparraltype in the dense chaparral. in Arizona is cattle grazing. Allotment size and grazing The study area was open to bear hunting each au- intensities are established by the Forest Service. A tumn but no bears, markedor unmarked,were known in the portion of the study area is on the Three Bar Wildlife to have been takenduring the study. Bear hunting Area, where no livestock grazing has been permitted dense chaparralwas evidently difficult and unproduc- since the mid-1940s. Bear hunting is allowed on the tive. Even hunters with bear hounds had low success hounds in entirestudy areain season (1 September-1December). rates because of the difficulty in following the heavy brush. The last known bearkilled by a hunter MATERIALSAND METHODS on the study area was taken in 1971. One markedsub- Bears were captured with foot snares and im- adult male, however, was taken during the 1976 bear mobilized with Semylan (phencyclidinehydrochloride) season about 100 km northwestof the study area. This at a dosage rate of 1.10 mg/kg of body weight. was the only marked bear known to have been har- A first premolar was extracted from each captured vested since the study began. bear and age was determinedby the cementum layer On the grazed portion of the study area, bears could technique (Stoneberg and Jonkel 1966). be taken legally any time of year by livestock BLACK BEAR ECOLOGYIN CHAPARRAL* LeCount 177 operators, under a depredationclause of the Arizona ferences in sample size, and the spread of home range law. This clause allowed a cattlemanto remove, at any size within any one age-class make direct comparisons time and by any means, any bear killing his livestock. difficult. Amstrup and Beecham (1976:345) suggest However, since the study began, no depredatingbears that the quantity, quality, and distributionof food, as were reportedtaken under this law. This fact does not influenced by climate and topography, probably deter- necessarily mean that no bear were taken by ranchers, mine minimum home range size. Our data appearedto however, since some rancherswere known to be reluc- support this hypothesis. The chaparralwith its great tant to reportthe taking of bears because of criticismby diversity of berry- and mast-producing species pro- protectionists.Some bears were killed on the study area duced a wide variety of foods available to bears from by ranchers prior to the study but exact figures were springthrough fall. As a result, bears were able to meet unobtainable.Total mortalityattributable to huntingby all seasonal food requirementswithin relatively small either sportsmen or ranchers, however, appears to be areas. low at present. The low harvest level probablyaccounts for the rela- Home Range Overlap tively high proportion(68 percent) of adults (3 + years Radio-locations suggested considerable overlap in of age) found in the population. In areas where bear the home ranges of adult males (Fig. 2), a phenomenon populations have been exploited more heavily by hunters, investigators have reported subadult:adultratios approaching50:50 (Erickson and Petrides 1964, Kemp 1970, Jonkel and Cowan 1971). However, in relatively unexploited populations, as many as 70 percent of the animalshave been found to be adults (Beecham 1980).

Home Range Sizes Estimatedhome range sizes, as computedby the use of a minimum size polygon that calculated the area from the sum of the areas of interior triangles, for 11 adult and 8 subadult bears, are shown in Table 1.

Table 1. Home range data for 19 black bears on the Four Peaks, Arizona, study area, based on radio-locations.

Home range size Number of (km2) Age-class Number radio- of bears locations Mean Range

Adult male 6 327 29 15-69 Adult female 5 380 18 10-30 Subadultmale 5 193 42 19-64 Subadultfemale 3 147 13 10-19

Sudadult males appeared to have the largest home

ranges followed in descending order by adult males, Fig. 2. Home range overlap of 6 adult male black bears on the Four Peaks, adult females, and subadult females. Although there Arizona, study area. were marked differences in mean home range sizes between age-classes, there was considerable overlap also reported from Idaho by Amstrup and Beecham among individuals. (1976:346). Overlap was less pronouncedin Montana Home range size for adult black bears has been de- (Jonkel and Cowan 1971:35) and Washington(Poelker terminedby other investigators (Erickson and Petrides and Hartwell 1973:73). Adult females appearedto have 1964, Jonkel and Cowan 1971, Poelker and Hartwell more distinct home ranges than males (Fig. 3). Some 1973, Amstrup and Beecham 1976). However, the degree of overlap occurred but on a lesser scale than variety of methods used to determinehome range, dif- among adult males. 178 BEARS - THEIR BIOLOGYAND MANAGEMENT

scrubtype, 1 at approximately1,200 m and the other at slightly less than 700 m. Data from this study indicated that bears within this area began to enter dens approximately1 November, with the majorityof females denning before the males. Some bears remained active into early December but the majority of the population was denned by 15 Novembereach year, regardlessof presenceor absence of snow. In late fall, the ground normally was free of snow, daily temperaturesaveraged 15 C, and night temperatures-2 C. Den sites at the higher elevations received several light snowfalls (12-15 cm) during the winter, but the snow usually melted within 2 weeks. In Februaryand early March, bears were frequently observed lying outside their dens during the warm (12-15 C) midday hours. However, these bears did not appear to leave the den sites at such times. By 15 March, most bears began to emerge from their dens on a daily basis, but movements were confined to within 100 m of the dens. Movements from the dens gradully increasedin distance, and by 15 April, all bears, except females with cubs, had left their dens. Females with cubs remained at the den sites approximately30 days longer, not leaving until about 15 May. These denning dates are similar to those determinedby other investigators (Baily 1930, Gilbert 1952, Spencer 1955, and Fig. 3. Home range overlap of 5 adult female black bears on the Four Peaks, Erickson 1965, Jonkel and Cowan 1971, Amstrup Arizona, study area. Beecham 1976, Lindzey and Meslow 1976).

CONCLUSIONS Intraspecifictolerance among bears was observed in the course of radiotrackingduring the study. Two adult The black bear is normallythought of in association males were observed traveling together on 7 different with a forest habitat. The Interior Chaparral in occasions, and adult females were observed togetherin Arizona, however, is a scrublandvegetation type com- 2 instances. Although agonistic behavior was not ob- posed primarilyof shrubs and low trees, interspersed and at served, it probably occurred between males because with a few forest species along major drainages It is of numerous many adult and subadultmales carriedthe wounds and the higher elevations. composed scars of battle. mast- and fruit-producingspecies, and when well developed it creates cover so dense as to be nearly im- Denning Behavior penetrable. the Fifty percent of the 24 dens located were on north- These are the virtues that appear to make The diverse fruit- and facing slopes, 25 percent on west-facing slopes, 17 chaparralexcellent bear habitat. an abundant percent on south-facing slopes, and 8 percent on east- mast-producingspecies not only provide excellent cover. facing slopes. All dens were dug under large boulders food supply each year but also provide a bear surrounded by dense vegetation. Two instances of As a result, this type is capable of supporting while at the same time bears using multiple dens during 1 winter were also density of at least 1 per 2.0 km2 observed. Most den sites were at elevations of 1,300- making it very difficult for hunters to overexploit the 1,500 m. However, 2 dens were located in the desert population. BLACK BEAR ECOLOGYIN CHAPARRAL* LeCount 179

LITERATURECITED JONKEL,C. J., AND I. MCT. COWAN. 1971. The black bear in the spruce-firforest. Wildl. Monogr. 27. 57pp. AMSTRUP, S. C., AND J. J. BEECHAM. 1976. Activity pat- terns of radio-collaredblack bears in Idaho. J. Wildl. KEMP,G. A. 1972. Black bear populationdynamics of Cold Manage. 40(2):340-348. Lake, Alberta, 1968-70. Pages 26-31 in S. HeiTero,ed. BAILEY,V. 1930. Animal life of Yellowstone National Park. Bears - their biology and management. IUCN Publ. Charles C. Thomas Publishers, Baltimore. 241pp. New Ser. 23. BEECHAM, J. 1980. Some population characteristics of LINDZEY, F. G., AND E. C. MESLOW. 1976. Winter dor- exploited and unexploited black bear populations in mancy in black bears in southwesternWashington. J. Idaho. Pages 201-204 in C. J. Martinka and K. L. Wildl. Manage. 40(3):408-415. Mc Arthur,eds. Bears- theirbiology and management. MCCAFFREY, E. R., G. B. WILL, AND A. S. BERGSTROM. U.S. Government D.C. Printing Office, Washington, 1976. Preliminarymanagement implications for black BROWN, D. AND C. H. LOWE. 1974. The Arizona E., sys- bears, Ursus americanus, in the Catskill region of New tem for natural and potential vegetation: illustrated York State as the result of an the ecological study. Pages summarythrough fifth digit for the North American 235-245 in M. R. Pelton, J. W. Lentfer, and G. E. Southwest. Arizona Acad. Sci. 9(3):1-56. Folk, Jr., eds. Bears - their biology and management. ERICKSON,A. W. 1965. The black bear in Alaska: its ecol- IUCN Publ. New Ser. 40. ogy and management. Alaska Dept. Fish and Game POELKER,R. J., AND H. D. HARTWELL.1973. The black Fed. Aid in Wildl. Restor. Prog. Rep., Proj. W-6-R-5, Work Plan F. bear in Washington. Washington State Game Dept. 19pp. Biol. Bull. 14. , AND G. A. PETRIDES. 1964. Population structure, 180pp. movements, and mortality of tagged black bears in SPENCER, H. E., JR. 1955. The black bear and its status in Michigan. Michigan State Univ. Agric. Exp. Stn. Res. Maine. Maine Dept. Inland Fish. Game Bull. 4. 55pp. Bull. 4:46-67. STONEBERG,R. P., AND C. J. JONKEL.1966. Age determi- GILBERT,D. L. 1952. Bear studies. Colorado Game and nation of black bears by cementum layers. J. Wildl. Fish Dept. Fed. Aid Quart. 1952 (Jan.):26-31. Manage. 30(2):411-414.