Grizzlybear food habits in the northernYukon, Canada

A. Grant MacHutchon1'3and Debbie W. Wellwood2'4

1237 CurtisRoad, Comox, BC V9M3W1, Canada 2p.O. Box 3217, Smithers,BC VOJ2NO, Canada

Abstract: We documented seasonal food habits of grizzly bears (Ursus arctos) in the Firth River Valley, Ivvavik National Park (INP), northernYukon, Canada, 1993-1995 using: (1) analysis of 176 scats, (2) 222 hours of direct observation,and (3) 99 feeding site investigations.In spring,the primary food were alpine (Hedysarum alpinum) roots and over-winteredberries such as crowberry (Empetrumnigrum). The main food plants in summer were common horsetail (Equisetumarvense) and bearflower(Boykinia richardsonii). Bears fed primarilyon bog blueberries (Vaccinium uliginosum), crowberries,horsetail, and bearflowerin fall. When blueberrieswere not available, grizzly bears dug for alpine hedysarumroots. In addition to eating plants, grizzly bears killed or scavenged caribou (Rangifer tarandus) and hunted Arctic ground squirrels(Spermophilus parryii) and microtines when available. Well used grizzly bear food plants in INP have similar nutritionalquality as food plants from southern Canada. However, the northerngrowing season is short, and suitable growing sites and diversity of major foods are generally less than in the south, so food availabilityis lower.

Key words: Canada,diet, food habits, grizzly bear, Ursus arctos, Yukon

Ursus 14(2):225-235 (2003)

Food and the search for it influence most behavior of As part of a larger research project investigating grizzly bearsduring their non-denning period. Nutritional grizzly bear seasonal habitat use, activity, and move- statushas a stronginfluence on populationdynamics; the ments for Ivvavik National Park (MacHutchon 1996, availabilityand quality of foods can affect a grizzly bear's 2001), we quantifiedgrizzly bear food habits. The intent mean age of reproduction,mean litter size, and breeding was to provide baseline documentationof bear ecology interval (Stringham 1986, Blanchard 1987, Stringham for the park's use in planning for increases in human 1990). Understandingfood habits is also importantfor visitors to the parkin the futureand to betterunderstand understandinggrizzly bear seasonal distribution and grizzly bear ecology in northernenvironments. habitatuse. Grizzly bears living in northernCanada and must contend with a short season of food availability, lack of protective cover, and extremes in Study area weather unlike bears living in southern Canada or the Ivvavik NationalPark (INP) encompasses 10,170 km2 at the contiguous United States. Northern bears may be northwesterntip of Yukon Territory, Canada, the particularlyvulnerable to changes in food availability bordering Arctic NationalWildlife Refuge (ANWR), because of the short time they have to acquire energy Alaska, USA, to the west and Beaufort Sea to the north necessary for maintenance, growth, reproduction,and (Fig. 1). The British Mountainsoccupy the central and winter denning. Understandingseasonal food habits of southern two-thirds of INP and rise to elevations of grizzly bears in the north may provide insight into how 1675 m. A band of flat to rolling topography10-30 km they adapt to this environmentand may be helpful for wide forms the coastal plain between the British assessing the potentialeffects of humanactivities, such as Mountains and the Beaufort Sea. This study was pri- oil andgas explorationand increasing tourism, on bearsin marily conducted in the British Mountainsof the Firth these areas(MacHutchon 2001). River Valley, but extended to other parts of the British Mountainsin INP. The FirthRiver (69?10'N, 140?05'W) flows northwardfor 160 km from its headwaters in Alaska to the Beaufort Sea. INP is characterizedby [email protected] [email protected] short, cool summers and long, cold winters. Mean

225 226 GRIZZLYBEAR FOOD IN THE YUKON * MacHutchon and Wellwood

alpine .Slopes above 500 m are - i sparselyvegetated. Cotton-grass (Erio- :j;;; phorum spp.) and sedge (Carex spp.) tussocks typically dominate low-angle -....:-:. , slopes or pediments. Mammalsof INP include caribouof the Porcupine caribou herd, .. / (Alces alces), muskox (Ovibos mo- schatus), Arctic ground squirrels,col- .- ' lared (Dicrostonyx torquatus) and

Sachs"Ha % brown lemmings (Lemmus sibiricus), >,^ r2: and northernred-backed (Clethriono- mys rutilus) and singing voles (Micro- tus miurus). Anadromous and non- anadromousDolly Varden char (Sal- velinus malma)occur in the FirthRiver Sas;t:P' well as other major rivers of INP. Phulatuk

Methods We documented grizzly bear diet using a combinationof (1) scat analysis, (2) direct observation,and (3) feeding site investigations to reduce biases ron oodHope associated with each technique. We *& % collected scats of known age during ornw Wets capture,ground investigations of radio- F Fon Nomans collared grizzly bear locations, or after observingunmarked bears. We collect- <-f/ ed some scats opportunistically and ,; aged them by considering local bear \ activity, the moisture content of the N.W.T. scat, condition of vegetation underthe scat, decomposition,and recentrainfall Fig. 1. Location for the study of food habits of grizzly bears in Ivvavik (Holcroftand Herrero1991). No Amer- National Parkshowing the FirthRiver Valley in northernY ukon,Canada. ican black bears (Ursus americanus) were in our study area. annual temperatureis -10?C (6.5?C in summer,-25?C We used only scats <14 days old for analysis in winter) and mean annual precipitationis 300 mm. following the methods of MacHutchon (1989). Scats Vegetation of the British Mountains includes open- were rinsed on sieves to remove fruit dye and fine di- forest subarctictaiga, treelessarctic tundra, and the broad gested material,then suspended in water. The percent transition zone between the 2 referred to as treeline volume of each diet item was visually estimated from (Pielou 1994). Trees become smallerand more scattered three to five 10-ml samples, then averaged. Diet items with increasinglatitude, and white (Picea glauca) were identified to the finest taxonomic level possible. and balsam poplar (Populus balsamifera) reach their Most plants were identified to species using reference northernlimit within the British Mountains along the plants collected in the field, but grasses and sedges lower Firth River Valley. Forests are most common on were recordedas graminoids.Mammal hair was identi- valley bottoms and southern-facing slopes and are fied using the methods of Weir (1995). Most mammals replacedby shrubcommunities with increasinglatitude. were identifiedto species, but voles and lemmings were Thereis an elevationtransition from well vegetatedvalley recordedas microtines.Percent occurrence was the num- bottoms through low shrub-dominatedcommunities to ber of scats with a diet item divided by the total number

Ursus 14(2):225-235 (2003) GRIZZLYBEAR FOOD IN THE YUKON * MacHutchonand Wellwood 227 of scats. Percentvolume was the mean volume of a diet as percentnitrogen multiplied by 6.25. Neutraldetergent item among all scats. fiber (NDF) was estimatedusing a modified Van Soest During June 1993, we fitted 5 adult female and 3 method (Robbins 1993). Similar analysis methods were adult male grizzly bears with radiocollars (Telonics, used for samples from the FlatheadRiver Valley, British Mesa, Arizona, USA). In late August 1995, we re- Columbia,Canada (McLellan and Hovey 1995). Regres- captured all radiocollaredbears and removed collars. sions of crudeprotein levels of plant species collected in MacHutchon (2001) described methods for focal bear INP and the Flathead River Valley during 2-week observation. We located radiocollared bears from samplingperiods were comparedusing equationsin Zar aircraft; then 1-2 backpacking crews of 2-3 people (1996). each were flown by helicopter to locations where they We delineated grizzly bear seasons of activity by could watch individual bears. We chose bears for general shifts in diet as determinedfrom scat analysis observationbased on the number of previous observa- and observations of bears and by the phenological tion sessions for each bear each season, its location developmentof food plants (MacHutchon1996). Spring inside or outside the study area, and the feasibility of lasted from 26 May to 15 June, summerfrom 16 June to maintaininga good vantage without disturbingthe bear. 31 July and fall from 1 August to 4 September.The start Unmarked bears were observed opportunistically,but of spring and end of fall were based on the start and data were not includedin our food habits analysis. Bears end of data collection. The change from spring to sum- were followed if they moved, and we continued to mer correspondedwith the widespread availability of observe as long as possible (up to 35 hours). We common horsetail shoots and the general shift in diet recorded foods eaten by bears during observations from roots to horsetail and forbs. The change from whenever possible. Frequently, however, a bear was summer to fall corresponded with the widespread too far away or viewing conditions were such that foods availability of bog blueberriesand the general shift in could not be distinguished. The most common food diet to berries.Phenology was fasterin the southernpart plants in a patch were often easiest to see; therefore,less of the study area than the northernpart because of the common plantsmay have been eaten but not seen. If two influenceof the cold Arctic Ocean, and therewere slight common foods occurred in a patch and the observer differences in dates among years. The specific dates could not tell which was being eaten, the food was used to delineate seasons generally reflected plant recordedas unknown forb, root, or berry. phenology in the central part of the study area where We identifiedfoods eaten by grizzly bears at feeding food plants were collected for nutrientanalysis. sites during ground investigations. Only feeding sites documented independently of focal bear observations were included in this analysis to maintain indepen- Results dence between the two methods. Some evidence of feed- Grizzly bear diet items in INP were placed into 8 ing was more obvious and persistedlonger; therefore,it of the 11 major food categories used by Mattson et al. may have been recorded more often (such as alpine (1991) and were the same 8 used by McLellan and hedysarumroot digging). Percentfrequency of use was Hovey (1995; Table 1). Additional categories in this the numberof sites where a food was eaten dividedby the study were "unidentifiedanimal" and "other."Other in- totalnumber of feeding sites. We recordedup to 3 foods at cluded debris collected incidentally with scats, grizzly each site so the totalof percentfrequencies was not 100%. bear hair, and unidentifiedmaterial. Common horsetail shoots, bearflower leaves and In spring,alpine hedysarum roots, over-wintered crow- flowers, alpine hedysarum roots, and bog blueberries berries,and horsetail shoots, primarily common horsetail, were collected at a location in the centralpart of the Firth were dominantfood plants in scats. Alpine hedysarum River 2-3 weeks Valley every duringJune-August 1994. root was the most frequently eaten food during focal Each was a collection of several sample individualplants observations and the most common food at feeding andbearflower and leaves, flowerswere combinedduring sites. We did not often see bearsfeeding on crowberries, analysis. Proximateanalyses of plant samples were done but they were common at feeding sites. Graminoidsand at the Department of Animal Science, University of caribouoccurred frequently in scatsbut in small volumes. BritishColumbia, British Vancouver, Columbia,Canada. Caribou was the most frequent mammal eaten during Gross was energy determinedwith a bomb calorimeter observationsand at feeding sites. and nitrogen content was estimated by the macro- In summer, horsetail shoots and bearflower leaves Percentcrude Kjeldahltechnique. proteinwas estimated were dominant food plants in scats, during focal

Ursus 14(2):225-235 (2003) 228 GRIZZLYBEAR FOOD IN THE YUKON * MacHutchonand Wellwood i observations,and at feeding sites. Bears were observed when first seen after denning. We do not know whether feeding on the flowers and leaves of bearflower, but the cub died from naturalcauses and was consumed or flowers were rarely detected in scats. Graminoidswere was preyed on. frequentlyfound in scats, but usually in small quanti- Alpine hedysarumroots were highest in crudeprotein ties. Bog blueberries started to show up in scats and in spring and early summer(Fig. 2). When horsetailand at feeding sites in late summer.Adult and larval wasps bearflowershoots first emerged, they had higher levels B. (family Vespidae) or bumblebees (Bombuspolaris, of crude proteinthan alpine hedysarumroots, but crude were found in a numberof but hyperboreus) scats, they protein in horsetail and bearflower steadily declined madeup a smallvolume. Arcticground squirrels were the over summer.Fiber was lower in bearflowerthan horse- most mammal in scat sum- frequent samples during tail and both were lower than alpine hedysarumroots. mer.Caribou meat scats were collectedwhen found, rarely We found no difference in the regression of crude so caribouwas under represented. protein to date of common horsetail between the Firth In fall, bog blueberry,alpine hedysarum,bearflower, River Valley, INP and the FlatheadRiver Valley, south- and horsetail were dominant food plants in scats. east British Columbia, Canada (Fig. 3; B. McLellan, Blueberriesand alpine hedysarumroots were the most BritishColumbia Ministry of Forests,Revelstoke, British common foods duringfocal observationsand at feeding Columbia, Canada,unpublished data; slope: t = 0.236, sites. Bearflower and horsetail were primarilyeaten in v = 10, P > 0.05, elevation: t = -0.278, v = 11, P > early fall, and blueberriesand alpine hedysarumwere 0.05). hedysarumroots had higher crude protein eaten throughout fall. Crowberries occurred often at Alpine than (Hedysarum sulphurescens) feeding sites, but were never recorded during observa- yellow hedysarum roots from the FlatheadRiver Valley in spring,but they tions likely because they often grew with bog blue- were similar in summer fall, so there was no berry and it was hard to distinguish between the two. through difference in t = -0.472, Arctic groundsquirrels were the most frequentmammal significant regressions (slope: = t = v = P > in scats and at feeding sites during fall. We ceased v 6, P > 0.05, elevation: 1.674, 7, 0.05). from the FirthRiver and collecting scats and makingground observations in early We includedbearflower Valley from the Flathead September, but observations of radiocollared grizzly cow-parsnip (Heracleum maximum) most bearsduring aerial locations in late fall suggestedfeeding River Valley together because they were the on alpine hedysarumroots and Arctic ground squirrels commonly eaten summerforb in theirrespective ranges. increased as bog blueberryavailability decreased when These plants had the same rate of decline in crude frost damage caused them to drop. On two occasions protein(t = -0.759, v = 9, P > 0.05), but the amountof grizzly bears were seen from the air feeding on caribou crude proteinwas significantlyhigher in cow-parsnipin carcassesin late fall. No moose remainswere identifiedin late summer and fall (t = -5.001, v= 10, P < 0.05). fall scats; however, a radiocollaredfemale grizzly bear Small sample sizes precludedtesting for differences in in was observed feeding on an adult bull moose carcass crude protein between bog blueberry and black were found at 2 early fall 1995, and moose remains huckleberry(Vaccinium membranaceum). feeding sites. On two occasions MacHutchon (1996) documentedgrizzly bears feeding on Dolly Vardenchar in INP. Discussion There was some variation among years in grizzly Scat data is commonly presented as per- bear food use in INP. In 1993, wasps occurred much analysis cent volume of food items (Hamer and Herrero 1987, more in scats thanin 1994 or 1995. Microtine frequently Mattsonet al. 1991, McLellan and Hovey 1995). How- populations peaked in 1995 (MacHutchon 1996) and ever, volume data can be misleading because of differ- grizzly bears fed on them more than in 1993 or 1994. ences in digestibility among foods. Poorly digested Bog blueberry production was reduced in 1995, ap- foods such as roots and graminoids can be over re- parentlybecause of late springfrost (MacHutchon1996); and highly digested foods such as meat can consequently, grizzly bear use of alpine hedysarum presented, be under (Hechtel 1985, McLellan and roots was higher in fall 1995 than in 1993 or 1994. represented bear observationand site data One scat collected at a radiocollaredadult female's Hovey 1995). Our feeding of food use in our and den site not includedin Table 1 was entirelygrizzly bear were different measures study scat data bias. However, hair with 4 cub claws. The female was observed breed- compensatedfor some sample sizes were small and observationand feeding site data ing the previous spring, but she was without cubs Ursus 14(2):225-235 (2003) 4_ Table 1. Percent volume (% V) and percent occurrence (% 0) of diet items in scats, the proportion of time grizzly bears fed on foods during [^ observations, and the percent of feeding sites where foods were used, Ivvavik National Park, Yukon, Canada, 1993-95. A dash indicates the ,, item was not identified for that period. kii Scat analysis Focal observations Feeding sites Springa Summera Falla Spring Summer Fall Spring Summer Fall ?= (n = 29) (n = 87) (n = 60) (19 hrs) (103 hrs) (100 hrs) (n = 29) (n = 28) (n = 42) Food items %V %O %V %O %V %O % % % % % % Roots Alpinehedysarum 44.8 65.5 1.6 6.9 12.4 43.3 79.1 0.5 25.8 72.4 17.9 38.1 Unidentified root - - 0.9 3.4 - - 0.1 0.1 0.4 - - 2.4 Graminoids 1.6 34.5 2.9 62.1 4.1 56.7 0.0 1.9 0.1 - 3.6 Horsetail 20.7 34.5 44.2 83.9 13.4 78.3 2.0 43.6 7.1 3.4 53.6 7.1 0 Forbs Bearflower 5.2 6.9 41.7 77.0 31.1 75.0 - 41.3 2.8 3.4 32.1 7.1 N Mountain sorrel (Oxyria digyna) - - 0.3 12.6 2.2 18.3 - 0.1 2.8 - - Unidentifiedforb 0.1 3.4 0.8 10.3 1.2 8.3 10.2 3.7 1.4 - -

Fruit ~o tl Bearberry (Arctostaphylos spp.) 0.2 6.9 - - - - - 3.4 3.6 o Kinnikinnick(Arctostaphylos uva-ursi) 0.2 3.4 0.1 1.1 0.0 1.7 - - - 3.4 - Crowberry 23.8 44.8 0.0 3.4 1.7 26.7 1.3 0.1 - 17.2 26.2 Red currant (Ribes triste) - - - - 0.0 1.7 - - - Soopolallie (Shepherdia canadensis) - - - 2.5 10.0 - - - - - 2.4 0 Bog blueberry 0.0 3.4 2.3 16.1 29.7 86.7 - 4.5 30.4 - 3.6 47.6 -A Lingonberry (Vaccinium vitis-idaea) 0.0 3.4 0.0 2.3 - - - - - Unidentifiedberry 0.1 6.9 0.0 2.3 0.0 1.7 5.0 1.3 25.6 3.4 0 Insects - - 1.6 9.2 0.0 3.3 - - - 3.6 Rodents z Microtines 1.9 6.9 0.0 5.7 - - - - 3.4 Groundsquirrel 0.6 6.9 0.9 11.5 0.5 15.0 - 0.0 0.0 - 10.7 19.0 I Ungulates Caribou 0.6 13.8 1.6 5.7 0.0 1.7 1.2 2.9 0.4 13.8 3.6 Moose ------3.3 - 3.6 2.4 Unidentifiedanimal 0.0 3.4 0.1 3.4 1.1 3.3 0.9 0.1 0.0 3.4 3.6 Other 0.0 3.4 1.0 8.0 0.0 5.0 - - - aSpring= 26 May to 15 Jun; Summer= 16 Jun to 31 Jul; Fall = 1 Aug to 4 Sep. I

230 GRIZZLYBEAR FOOD IN THE YUKON * MacHutchon and Wellwood

30- -- -Alpine hedysarum servation and feeding site data. For "-- Barflower these reasons, our methods not be -- Commonhorsetait may 25 - --0-Bog blueberry entirely independent and our results may not represent the population as 20- a whole. there are fewer a Nevertheless, 0 major foods in the north than the south la - t: 15 (McLellan and Hovey 1995), so there is less chance we missed common O1f any 10- ones. Grizzly bear food habits have been 5- described for other mountainous areas of northern Alaska and Yukon, in- a I l cluding the western Brooks Range, 50- v? -i Alaska (Hechtel 1985), British Moun- 45 - tains of ANWR, Alaska west of INP

40 - 1987), and Barn 0 (Phillips Range, 35 - A Yukon east of INP (Nagy et al. 30- 1983a). Similar to this study, a com- A + * mon food in all studies was 25 - spring 5- roots. However, 20- alpine hedysarum during one year bears more frequently 15 - 2 dug Oxytropis viscida (also called 10 - Oxytropis borealis) roots in the west- 5- ern Brooks Range (Hechtel 1985). 0 4 4 f ? t -t I Over-winteredberries were well used in 2 studies. In the Barn Range, - 6.0 crowberrieswere the most used (Nagy et al. but in the western Brooks 5.0- 1983a), 0C - n E% o 0 Range bearberries(Arctostaphylos ru- _--_ | 4.0 - bra or A. alpina) were most used (Hechtel 1985). Over-winteredberries 3,0 - are likely important spring foods be- cause they are high in carbohydrates I 2.0- f (Hamer and Herrero 1987). As in our

o 1.0 - study, caribou were a well used spring food in ANWR (Phillips 1987). In the 0.0 I i -t I I I t western Brooks Range cotton-grass 1-14Jun 15-28Jun 29Jun- 13-26Jul 27Ju -9 10-23 24Aug- flowers were 12 Jul Aug Aug 7 Sep (Eriophorumvaginatum) Date eaten extensively by one family group one year (Hechtel 1985). Cotton-grass Fig. 2. Percent crude protein, percent neutral detergent fiber, and was abundantin INP, but we found no gross energy of 4 grizzly bear food plants from the central Firth River evidence it was eaten, nor did Phillips National 1994. Valley, Ivvavik Park, Yukon, Canada, June-August (1987) in ANWR. Grizzly bears in INP had a similar summer diet to bears in the western Brooks Range were only from 5 grizzly bears. One other radiocollared ) and ANWR In the Barn bear dropped his collar early in the study and 2 others (Hechtel 1985) (Phillips 1987). bears fed almost on frequently were not observed because they were off Range, however, grizzly entirely the habitat-mappedportion of the study area. Individual grass in summler, even though horsetail and bearflower variationin bear behavior may have biased observation were available (Nagy et al. 1983a). Grizzly bears in INP data (MacHutchon2001). In addition, 72% of scat sam- and in souther populations feed on insects ples came from the 5 grizzly bears used for focal ob- during summer (Hamilton and Bunnell 1987, Hamer et

Ursus 14(2):225-235 (2003) GRIZZLYBEAR FOOD IN THE YUKON * MacHutchon and Wellwood 231

20 - fall foods in the Barn Range, but alpine

15 - hedysarum roots and Arctic ground 0 * squirrels were also used (Nagy et al. - * 10 1983a). Nagy et al. (1983a) suggested 5- * Alpine hedysarum INP the scarcity of bog blueberry use *Yellow hedysarum - Flathead their was due to t ! during study poor O0 t i t I t I I I t Bearberries and - blueberry production. 35 were in how- 30 - soopolallie present INP; 25 - ever, bog blueberry and crowberry 20- were much more widespread and 15- O abundant.Similar to other studies, use 10 - 1- 1 Bearflower- INP of alpine hedysarum roots and Arctic 5- Cow-parsnip - Flathead ground squirrelsincreased through fall 0 0 - I I t I F F I F I i I I i in our and alpine hedysarum 35 - study, 0aO roots were more used when 30- * frequently 25 - bog blueberryproduction was reduced. 20 - Mammals are likely the highest 0 15- quality food throughout the year *Common horsetail - INP * (McLellan and Hovey 1995, Hilder- 5 | * Commonhorsetail - Flathead 0 Ft l I F I I F I t F F t brand et al. 1999), but their ease of

7- captureand relative availability in INP

6- 0 varied among seasons (MacHutchon Radiocollared bears 5- 2001). grizzly considerable time Arc- 4- spent pursuing tic or microtines dur- 3- ground squirrels ing summerand fall (called "foraging" 2- * Bog blueberry - NP - but I * Black huckleberry Flathead in MacHutchon 1996, 2001), feeding time in Table 1 is low be- 0 F- t I I1 I I I t I, t t' t t ou rv It ? I cause they were quickly consumed. ct cocy c3 u a^ 8 -i 5 Caribou were primarily available for Date a short time in spring when migrating northwest through INP to calving Fig. 3. Seasonal crude protein of the same (or similar) grizzly bEsar grounds on the Arctic Ocean coast National Yuk? food plants from the Firth River Valley, Ivvavik Park, on, and in summerwhen large groups with Canada and the Flathead River south-east Britiish (INP) Valley, calves southeast INP Columbia, Canada (Flathead; B. McLellan, British Columbia Ministry migrated through of Forests, Revelstoke, British Columbia, Canada, unpublished datta). to summer range (Russell et al. 1993). When available, grizzly bears focused considerable effort on obtaining cari- Hutchon We observed or found al. 1991, Mattson et al. 1991, McLellan and Hovey bou (Mac] 2001). hat caribou were obtained in a number of 1995). Hechtel (1985) found only a few instances of evidence t )ou were and killed bears insect feeding and Nagy et al. (1983a) found none. ways. Cari surprised by grizzly ved down tree or shrub draws toward Alpine hedysarum roots, bearberries, and Arctic as they mo major ibou calves from their mothers at ground squirrels were the most common fall grizzly rivers. Car separated rivers or river bear foods in the western Brooks Range (Hechtel aggregatioris beside during crossings and bears. 1985). Crowberries, bog blueberries, and bearberries became pre-y to wolves (Canis lupus) grizzly rivers were commonly eaten in early fall in ANWR and alpine Caribou of all ages died or were injured crossing hedysarum roots, Arctic ground squirrels, and micro- and were sc,avenged or killed. Grizzly bears occasionally tines were more commonly eaten as fall progressed caught and killed adult caribou in open country chases (Phillips 1987). Grasses, crowberry, and some soopo- and took o ver carcasses killed by wolves. Grizzly bears lallie (Shepherdia canadensis) were the most common in east cenltral Alaska killed about 4 times more moose

Ursus 14(2):225-235 (2003) 232 GRIZZLYBEAR FOOD IN THE YUKON * MacHutchonand Wellwood and caribou biomass than they scavenged, and appro- protein in a food item (Pritchardand Robbins 1990). priatedand consumed more carcasses of animals killed NDF measures the amount of insoluble fiber in plants by wolves than they lost to wolves (Boertjeet al. 1988). (hemicellulose, cellulose, lignin, and cutin), but it does Abundantmeat resourcespositively affect body size, not measure soluble fiber, such as pectins and gums, reproductivesuccess, and populationdensity of grizzly that are not digestible by grizzly bears (Pritchardand bears and thereforepositively influence habitat quality Robbins 1990, Robbins 1993). Total dietary fiber is a (Hilderbrandet al. 1999). Northerngrizzly bearsthat feed bettermeasureof allnondigestibledietary fibers; however, on caribou on a regularbasis have higher densities and we used NDF because the cost of total dietary fiber productivitythan populations that do not feed on caribou analysis was prohibitive.Our NDF values, therefore,are (Reynolds and Gamer 1987). MacHutchon (2001) not a true measure of nondigestible plant fiber, but suggested the availability of mammalianprey, such as they do reflect relative differences in fiber over time. caribou, Arctic ground squirrels,and other small mam- Pritchard and Robbins (1990) found that as total mals, may compensatefor the constraintsof latitude in dietary fiber increased, dry matter digestibility and northernbear populations. Hechtel (1985) andNagy et al. digestible energy decreased. (1983a) found only small amountsof caribouin scats,but Bunnell and Hamilton(1983) suggested grizzly bears suggested caribou were under representedin scats and change food plants with seasons in response to changes their and in- actually were a more common food. Caribou were the in digestibility to optimize energy protein take. McLellan and availabil- primary food of grizzly bears in the central Canadian Hovey (1995) suggested and and time Arcticduring most of theiractive season (Gauet al. 2002). ity (distribution abundance) handling may have a influence on selection Arctic groundsquirrels were commonly eaten by grizzly greater forage by grizzly bears than and protein). We bearson the northerncoastal plain of the PrudhoeBay oil quality (digestible energy bears of INP their diet season- fields, Alaska (Shideler and Hechtel 2000) and the suggest grizzly changed ally based on trade-off between food quality and di- TuktoyaktukPeninsula and RichardsIsland, Northwest gestibility, as well as availabilityand handlingtime. We Territories (Nagy et al. 1983b). R. Shideler (Alaska focus our discussion on frequently eaten foods that Departmentof Fish and Game, Fairbanks,Alaska, USA, providedigestible energy and protein,but recognize that communication,2003) suggested small mam- personal some foods eaten in small quantities or infrequently Arctic may compen- mals, particularly groundsquirrels, be importantin providing essential vitamins and seen in the may sate for the lower predationrates on caribou minerals. Prudhoe than othernorthern areas. Bay region Grizzly bears fed on alpine hedysarumroots in spring food habits is Variationin grizzly bear among years when roots were highest in crude protein.They also fed andDean Hamer common(Hechtel 1985, Stemlock 1986, on alpine hedysarumroots in fall when protein levels and Herrero 1987, Mattson et al. 1991, McLellan and were lower, but fiberwas also lower, which likely meant Hovey 1995). In Denali NationalPark, Alaska, (Stemlock a higher proportion of crude protein and energy and Dean 1986) and the PrudhoeBay oil fields (Shideler was digestible. In addition, there were few above- and Hechtel 2000), Arctic ground squirrelpopulations groundvegetation alternatives to alpine hedysarumroots were relativelystable and consistentlyavailable to bears, in early spring and late fall. Hamer and Herrero(1987) but microtine and large mammals were less predictable also found crude proteinof alpine hedysarumroots and and lowest in prey items. This relativeavailability of mammalianprey grizzly bear use was highest in spring was true for our study area as well. During years of summer. abundantmicrotines in the PrudhoeBay region, Shideler Grizzly bears in INP used horsetailand bearfloweras in small and Hechtel (2000) observeda relativelyhigh proportion soon as they were availableabove ground,even more switch to these of grizzly bearsfeeding on microtineadults and young in amounts, but made a significant summer.At nests, but also on the caches of collected by plants from alpine hedysarumroots in early adult microtines.Hamer and Herrero(1987) also found that time, horsetail and bearflower were much more so time was shorter thatgrizzly bearuse of alpine hedysarumroots increased widespreadand abundant, handling in- in Banff NationalPark, Alberta, during years of low berry (MacHutchon 2001) with correspondingly higher et al. In stored production. Weather and microclimate can influence take rates (Rode 2001). addition,protein was immobilized for stem berryproduction by affectingpollinators and flowerbuds in alpine hedysarum roots in late (Martin1983, Stemlock and Dean 1986). and leaf growth and flowering spring, thereby to bears. The and The amount of digestible protein available to grizzly reducingthe amountavailable protein content of horsetail and bearflower in early bears is positively correlatedwith the amount of crude energy Ursus 14(2):225-235 (2003) GRIZZLYBEAR FOOD IN THE YUKON * MacHutchonand Wellwood 233 summer was not that different than alpine hedysarum affect the time availableto acquireenergy necessary for roots, but fiber was lower in the former so digestibility maintenance,growth, reproduction, and hibernation (Mac- likely higher. By mid-August feeding on horsetail and Hutchon 2001). Constraintson their ability to forage, bearflower had declined and there was an increase in particularlyon meat sources, could have individual or feeding on alpine hedysarum roots again. This corre- long-term population implications (Hilderbrandet al. sponded to a period when nutrientquality of horsetail 1999). Grizzly bears in INP appearto fear humans and and bearflower was lower than for alpine hedysarum. generally have not habituatedto human activity; they Protein content of horsetail and forbs commonly de- can be easily displaced from importanthabitats or prey clines over summer(Hamer and Herrero1987, McLellan (MacHutchon 1996, 2001). Grizzly bears in the north and Hovey 1995, Rode et al. 2001), but some areas have limited vegetative security cover and no darkness with drifted snow have delayed phenology and there- during most of their non-denningperiod to reduce the fore may have high quality horsetail and forbs avail- displacementeffects of humanactivity (McLellan 1990). able into fall (Shidelerand Hechtel 2000). This suggests a need to carefully manage human Newly ripened berries were eaten only in fall, the activities to minimize their effects on bears or their only time they were available.Bog blueberrieslikely were importantfoods, particularlymammalian prey. preferredover other berries because plants were wide- Tourists can disrupt grizzly bear feeding on caribou spread and abundant,therefore intake rates were high when people travelon northernrivers in summer.During (Welch et al. 1997), particularlyin years of good berry this time, caribou herds cross rivers between calving production. Blueberries also were low in fiber and grounds and summerranges and are killed by bears or high in gross energy (i.e., carbohydrates),which can be scavenged when they die during the crossing. For importantfor fat deposition prior to denning (Hamer example, in July 2002 more than 20 adult bull caribou and Herrero Welch et al. 1987, 1997, Rode and Robbins died while swimmingacross the lower FirthRiver in high Bears can not 2000). significantlyincrease their fat stores water and an almost equal numberof bears moved in to on alone because are non-cecal foliage they monogas- feed on the carcasses. Parks Canada staff temporarily trics that cannot fiber and digest efficiently (Bunnell closed the lower river to raftingto minimize disturbance Hamilton 1983, Welch et al. 1997). Hamer and Herrero of the bearsand to ensurehuman safety (S. Travis,Parks (1987) also found grizzly bears used blueberriesmore Canada,Inuvik, Northwest Territories, Canada, personal frequentlythan alpine hedysarumroots when both were communication,2002). Travelersshould be encouraged available. In the absence of easily obtained meat, to be cautiousabout where they camp andhike duringthe however, some alpine hedysarumroot or late developing summercaribou to avoid bearsfrom forb in the diet may provide protein and other minerals migration displacing carcassesand to avoid encounters. to offset the limitationsof a largely fruit diet (Rode and potentiallydangerous Robbins 2000). Decreased use of blueberriesin late fall Riverbanksand alluvial deposits along riversare common for was likely because they dropped off plants and were places ground squirrelcolonies (MacHutchon1996, no longer readily available (Welch et al. 1997). Arctic Shideler and Hechtel 2000), so travelers should be ground squirrelscan be an especially importantfood in encouraged to avoid these areas if possible. If people late fall when other foods such as berriesand vegetation hike on sparselyvegetated mountain ridges and stay away are not available (Shideler and Hechtel 2000). from vegetatedmountain slopes and valley bottoms,they Grizzly bears' food plants in INP were as nutritious can avoid areaswhere caribou kills areoften made as well as those from southernCanada; however, the northern as importantgrowing sites of alpinehedysarum, horsetail, growing season is short and suitable growing sites and bearflower,and bog blueberry. diversity of major foods are generally less than in the south (McLellan and Hovey 1995), so overall food plant availabilityis lower. Availability appearsto have Acknowledgments a greaterinfluence on diet selection in the norththan the Funding for this study was provided by Parks south because of these constraints(McLellan and Hovey Canada Agency, the Inuvialuit Game Council, the 1995). EnvironmentalInnovation Programof Canada's Green Plan, the Wildlife Management Advisory Council (North Slope), and the Northern Scientific Training Managementimplications Program.A significantproportion of the costs was Grizzly bears, in the north have a short study growing also borne by Parks Canada Agency through in-kind season to feed, so repeated disruptionsmay adversely contributions.We thank all the Parks Canada Agency Ursus 14(2):225-235 (2003) 234 GRIZZLYBEAR FOOD IN THE YUKON * MacHutchonand Wellwood staff, Inuvik, Northwest Territories that helped with HECHTEL,J.L. 1985. Activity and food habits of barrenground logistics and assisted in the field. We are particularly grizzly bears in Arctic Alaska. Thesis, University of grateful to B. Smith, V. Sahanatien,and I. McDonald Montana,Missoula, Montana,USA. C.C. C.T. M.E. for their dedication to and support of this study; S. HILDERBRAND, G.V., SCHWARTZ, ROBBINS, JACOBY,T.A. HANLEY,S.M. ARTHUR,AND C. SERVHEEN. Rogers, who entered all the observation data into 1999. The importanceof meat, particularlysalmon, to body a database,and K. McLaughlinand T. Skjonsberg,who size, productivity, and conservation of North assisted with grizzly bear We thank D. Jones, population capture. American brown bears. Canadian Journal of Zoology in I. Teske, and W. MacKenzie for all their hard work 77:132-138. her with scat the field and M. Kellner for help analysis. HOLCROFT,A.C., AND S. HERRERO. 1991. Black bear, Ursus Thanks also to all those individuals who graciously americanus,food habits in southwesternAlberta. Canadian volunteeredtheir time and assisted with the fieldwork. Field-Naturalist105:335-345. Thanks to A. Harestad of Simon Fraser University, MACHUTCHON,A.G. 1989. Spring and summerfood habits of Bumaby, British Columbia, and D. Humphrey of black bears in the Pelly River valley, Yukon. Northwest Camosun College, Victoria, British Columbia, for Science 63:116-118. bearhabitat use IvvavikNational their logistic support and lab space for scat analysis. . 1996.Grizzly study, Yukon:final WesternArctic District, Parks We are grateful to D. Shackleton, M. Evans, and G. Park, report. Northwest Canada. Galzi, of Animal Science, University of Canada,Inuvik, Territories, Department . 2001. bear and in the British Vancouver, British Columbia for Grizzly activity budget pattern Columbia, Firth River Yukon. Ursus 12:189-198. nutrient We thank B. McLellan, B.C. valley, plant analyses. MARTIN, P. 1983. Factors influencing globe huckleberry of Revelstoke, British Columbia, for Ministry Forests, fruit production in northwesternMontana. International his plant nutrientdata from the FlatheadRiver Valley, Conference on Bear Research and Management 5: British Columbia. R. Shideler and J. Hechtel provided 159-165. helpful commentson an early version of the manuscript. MATTSON,D.J., B.M. BLANCHARD,AND R.R. KNIGHT.1991. Food habits of Yellowstone grizzly bears, 1977-1987. Literaturecited CanadianJournal of Zoology 69:1619-1629. MCLELLAN,B.N. 1990. Relationships between human in- BLANCHARD,B.M. 1987. Size and patterns of the growth dustrial activities and grizzly bears. InternationalConfer- on Bear Yellowstone grizzly bear.International Conference ence on Bear Research and Management8:57-64. Research and Management7:99-107. , ANDF.W. HOVEY.1995. The diet of grizzly bears in BOERTJE,R.D., W.C. GASAWAY,D.V. GRANGAARD,AND D.G. the Flathead River drainage of southeastern British KELLEYHOUSE.1988. Predationon moose and caribou by Columbia.Canadian Journal of Zoology 73:704-712. A.M. M.C.S. KINGSLEY, radio-collaredgrizzly bears in east central Alaska. Cana- NAGY, J.A., R.H. RUSSELL, PEARSON, ANDB.C. GOSKI.1983a. Ecological studies of grizzly bears dian Journalof Zoology 66:2492-2499. in the ArcticMountains, northern Yukon Territory, 1972- BUNNELL,F.L., ANDA.N. HAMILTON.1983. Forage digestibility 1975. Canadian Wildlife Service, Edmonton, Alberta, and fitness in bears. InternationalConference on grizzly Canada. Bear Research and 5:179-185. Management . ,..., , AND C.B. LARSEN. 1983b. A R. CASE,D.F. PENNER,AND P.D. MCLOUGHLIN. GAU, R.J., study of grizzly bears on the barren-groundsof Tuktoyak- 2002. Feeding patterns of barren-groundgrizzly bears in tak Peninsula and Richards Island, Northwest Territories, the central CanadianArctic. Arctic 55:339-344. 1974 to 1978. Canadian Wildlife Service, Edmonton, HAMER,D., AND S. HERRERO.1987. Grizzly bear food and Alberta,Canada. bears habitat use in the front ranges of Banff National Park, PHILLIPS,M.K. 1987. Behavior and habitatuse of grizzly Conference on Bear Alberta. InternationalConference on Bear Research and in NortheasternAlaska. International Research and Management7:159-167. Management7:199-213. E.C. 1994. A naturalist's to the Arctic. The , ANDK. BRADY.1991. Food and habitatused PIELOU, guide University of Chicago Press, Chicago, Illinois, USA. bears, Ursus arctos, along the continentaldivide by grizzly PRrrCHARD, G.T., AND C.T. ROBBINS. 1990. Digestive and National Alberta.Canadian Field- in WatertonLakes Park, metabolic efficiencies of grizzly bears and black bears. Naturalist105:325-329. CanadianJournal of Zoology 68:1645-1651. HAMILTON,A.N., ANDF.L. BUNNELL.1987. Foraging strategies REYNOLDS, H.V., AND G.W. GARNER. 1987. Patterns of grizzly of coastal grizzly bears in the Kimsquitriver valley, British bear predationon caribouin northernAlaska. International Columbia.International Conference on Bear Researchand Conference on Bear Research and Management 7: Management7:187-197. 59-67. Ursus 14(2):225-235 (2003) GRIZZLYBEAR FOOD IN THE YUKON * MacHutchon and Wellwood 235

ROBBINS,C.T. 1993. Wildlife feeding and nutrition.Academic InternationalConference on Bear Research and Manage- Press, San Diego, California,USA. ment 6:33-39. RODE,K.D., ANDC.T. ROBBINS.2000. Why bears consume . 1990. Grizzly bear reproductiverate relative to body mixed diets during fruit abundance.Canadian Journal of size. International Conference on Bear Research and 78:1640-1645. Zoology Management8:433-443. , AND L.A. SHIPLEY.2001. Constraints on , WEIR,R.D. 1995. Diet, spatial organization, and habitat bears. 128:62-71. herbivoryby grizzly Oecologia relationshipsof fishers in south-centralBritish Columbia. RUSSELL,D.E., A.M. MARTELL,AND W.A.C. NIXON. 1993. Thesis, Simon FraserUniversity, Burnaby,British Colum- Range ecology of the Porcupine caribou herd in Canada. Canada. Rangifer Special Issue Number 8. bia, J. K.C. ANDC.T. ROBBINS.1997. SHIDELER,R., ANDJ. HECHTEL.2000. Grizzly bear. Pages 105- WELCH,C.A., KEAY, KENDALL, 132 in J.C. Truett and S.R. Johnson, editors. The natural Constraintson frugivoryby bears.Ecology 78:1105-1119. history of an Arctic oil field. Academic Press, New York, ZAR,J.H. 1996. Biostatisticalanalysis. Third edition. Prentice New York, USA. Hall, Upper Saddle River, New Jersey, USA STEMLOCK,J.J., ANDF.C. DEAN. 1986. Brown bear activity and habitat use, Denali National Park-1980. International Conferenceon Bear Researchand Management6:155-167. Received: 9 August 2002 STRINGHAM,S.F. 1986. Effects of climate, dump closure, and Accepted: 18 April 2003 other factors on Yellowstone grizzly bear litter size. Associate Editor: R.T. Shideler

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