Source: WASHINGTON STATE UNIVERSITY submitted to NRP
ASSESSING THE VALUE OF CUTTHROAT TROUT (A SPECIES AT RISK) TO GRIZZLY BEARS IN YELLOWSTONE NATIONAL PARK
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
0173900
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Jan 1, 2010
Project End Date
Dec 31, 2014
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
WASHINGTON STATE UNIVERSITY
240 FRENCH ADMINISTRATION BLDG
PULLMAN,WA 99164-0001
Performing Department
Natural Resource Sciences
Non Technical Summary
This study addresses critically important issues for the management of Yellowstone National Park. These issues include understanding the interaction and perpetuation of threatened grizzly bears and cutthroat trout in response to potentially dramatic changes created in this ecosystem by mankind outside of any purposeful management program. This study relies on the best talents of scientists from multiple agencies and universities, and has the potential to bring together a pool of money adequate to address such a complex biological issue. Probable duration: 2009 through 2014. Additional funding for this project is expected from USGS. Expected impacts: Yellowstone National Park is the nation's premier national park. Hundreds of thousands of people visit Yellowstone each year hoping to see a grizzly bear. This research will assist the park in maintaining a healthy grizzly bear population.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
1350830107025%
1360830107025%
1360860107025%
3150830107025%
Knowledge Area
135 - Aquatic and Terrestrial Wildlife; 136 - Conservation of Biological Diversity; 315 - Animal Welfare/Well-Being and Protection;

Subject Of Investigation
0830 - Wild animals; 0860 - Endangered species;

Field Of Science
1070 - Ecology;
Goals / Objectives
Yellowstone cutthroat trout (Oncorhynchus clarki) provide a source of highly digestible energy and protein for grizzly bears (Ursus arctos) that fish tributary streams to Yellowstone Lake during spring and early summer. Research from 1985-87 documented evidence of grizzly bears fishing on 61% of the 59 known spawning streams tributary to Yellowstone Lake. Those researchers concluded that 90% of the diet of bears frequenting streams was cutthroat trout, and that female bears were the primary users of this resource. Yellowstone Lake cutthroat trout are now at risk due to human introduced exotic lake trout and whirling disease. The population of cutthroat trout appears to be declining. In a recent study, we found that males are now the primary users of this resource and with the exception of a few individual bears, cutthroat trout are no longer a significant food resource for this bear population. However, we made several assumptions that led to above conclusions that are markedly different from the earlier study. Those assumptions need to be further refined and tested before concluding that the above results are correct and that increased efforts need to be made to assist cutthroat trout and, thereby, all their consumers. Here we propose to use advanced technology including global positioning system radio telemetry collars, biochemical assays to quantify fish consumption, additional captive bear feeding studies, and remote sensing devises to accurately quantify numbers and composition of grizzly bears utilizing and the value of the cutthroat trout resources of Yellowstone Lake.
Project Methods
Study Area: We propose to conduct this work in the Greater Yellowstone Ecosystem (GYE), which includes Yellowstone (YNP) and Grand Teton National Parks and adjacent federal, state, and private lands in portions of Montana, Wyoming, and Idaho. Population estimation: Population size will be estimated using mark - recapture methods. Multiple hair snagging sessions coupled with microsatellite genotyping analysis to determine species, gender, and individual identity of bear hair samples will provide the marks and recaptures. Trapping and Handling: Bears will be captured by qualified IGBST and Park staff following the established and approved animal welfare policy (Midcontinent Ecological Science Center Policy for Utilization of Animals in Research). Telemetry: Bears will be fitted with Telonics Global Positioning System (GPS Gen III-3600) transmitters equipped with spread spectrum technology. We will use geographic information system techniques to assess bear use of spawning streams both spatially and temporally. Feeding Site Visits: For both grizzly and black bears random GPS locations will be chosen for each bear each week to determine habitat and forage selection. Ground visits to GPS locations will record bear activity and sign along with foods consumed. Food items will be collected at feed sites and frozen. Items will be freeze-dried and ground via Wiley mill before being analyzed for crude protein, dietary fiber, gross energy, and ash (Pritchard and Robbins 1990). Foraging Activity, Fish Consumption: Bear activity associated with streams will be determined by documenting fish remains left by feeding bears, scats, and bear tracks along stream courses (Reinhart 1990). We will document use of randomly selected sections of stream by individual bears with remote cameras. Cameras will be deployed on sections of stream that are fished by bears. Feeding Trials Using Captive Grizzly Bears: Six, captive grizzly bears (3 male and 3 female siblings) will be used in a year-long feeding trial to determine the relationships between consumption rates of mercury-contaminated trout and bioaccumulation of mercury in hair, plasma and whole blood. Mercury, Isotope and Trace Element Analyses: Mercury concentrations will be determined on a nitric acid/hydrogen peroxide microwave assisted digestion of the freeze-dried biological material (blood, plasma, tissue) or the air dried hair samples followed by either cold vapor atomic fluorescence or cold vapor atomic absorption spectrometry. We will analyze hair, blood and food sources for the S isotopes following methods summarized in Kester et al. (2001) and for C and N isotope analyses following methods summarized in Fry et al. (1992).

Progress 01/01/10 to 12/31/14

Outputs
Target Audience: National Park Service and the general public Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Two (2) PhD students were produced. Ten (10) undergraduates assisted the PhD students in their field studies. How have the results been disseminated to communities of interest? The results have been published in the scientific and non-scientific presses. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Major goals of the project This study addressed critically important issues for the management of Yellowstone National Park. These issues included understanding the interaction and perpetuation of threatened grizzly bears and cutthroat trout in response to dramatic changes created in this ecosystem by mankind outside of any purposeful management program. This was due to the introduction of lake trout into Yellowstone Lake, previously the home of a large cutthroat trout population. Lake trout feed on cutthroat trout and have decreased the cutthroat trout population to less than 1% of its historic level. Cutthroat trout were available to many terrestrial and avian consumers, including grizzly bears, as they migrated into small, shallow streams to spawn. Lake trout spawn in deeper waters within the Lake and are never available to terrestrial predators. Similarly, wolves, while purposefully re-introduced to return the ecosystem to its historic functioning, have dramatically decreased the elk population. Elk calves to adults have been an important food resource for grizzly bears. Thus, two of the major, meat resources that grizzly bears have depended on in the past are greatly reduced. This study relied on the best talents of scientists from multiple agencies and universities to evaluate the consequences of these changes in the ecosystem. What was accomplished under these goals? Because park managers and the public are concerned about the impact created by reductions in foods consumed by Yellowstone's grizzly bears, we quantified bear diets to determine how bears living near Yellowstone Lake are adjusting. We estimated diets using: 1) stable isotope and mercury analyses of hair samples collected from captured bears and from hair collection sites established along cutthroat trout spawning streams and 2) visits to recent locations occupied by bears wearing Global Positioning System collars to identify signs of feeding behavior and to collect scats for macroscopic identification of residues. Approximately 45 ± 22% (x ± SD) of the assimilated nitrogen consumed by male grizzly bears, 38 ± 20% by female grizzly bears, and 23 ± 7% by male and female black bears came from animal matter. These assimilated dietary proportions for female grizzly bears were the same as 10 years earlier in the Lake area and 30 years earlier in the Greater Yellowstone Ecosystem. However, the proportion of meat in the assimilated diet of male grizzly bears decreased over both time frames. The estimated biomass of cutthroat trout consumed by grizzly bears and black bears declined 70% and 95%, respectively, in the decade between 1997-2000 and 2007-2009. Grizzly bears killed an elk calf every 4.3 ± 2.7 days and black bears every 8.0 ± 4.0 days during June. Elk accounted for 84% of all ungulates consumed by both bear species. Whitebark pine nuts continue to be a primary food source for both grizzly bears and black bears when abundant, but are replaced by false-truffles (Rhizopogon spp.) in the diets of female grizzly bears and black bears when nut crops are minimal. Thus, both grizzly bears and black bears continue to adjust to changing resources, with larger grizzly bears continuing to occupy a more carnivorous niche than the smaller, more herbivorous black bear. We also estimated numbers of grizzly bears and black bears that continue to live in the immediate Yellowstone Lake area. We estimated that 48 (95% CI=42-56) male and 23 (95% CI=21-27) female grizzly bears visited the historically fished tributary streams during our study. In any 1-year, 46 to 59 independent grizzly bears (8-10% of estimated Greater Yellowstone Ecosystem population) visited these streams. When compared with estimates from the 1997 to 2000 study and adjusted for equal effort, the number of grizzly bears using the stream corridors decreased by 63%. Additionally, the number of black bears decreased between 64% and 84%. We also document an increased proportion of bears of both species visiting front-country (i.e., near human development) streams. Thus, we continue to urge the Park Service to do all that is possible to remove lake trout and the recover the remaining cutthroat trout population.

Publications

  • Type: Journal Articles Status: Submitted Year Published: 2015 Citation: Rivet, D.R., O.L. Nelson, C.A. Vella, H.T. Jansen, and C.T. Robbins. 2015. Minimal systemic effects of a high saturated fat diet for grizzly bears (Ursus arctos horribilis). Journal of Comparative Physiology (submitted 5/26/2015).
  • Type: Journal Articles Status: Submitted Year Published: 2015 Citation: Teisberg, J.E., B.M. Kemp, C.C. Schwartz, M.A. Haroldson, C. Monroe, L.P. Waits, J.K. Fortin, R.D. Mace, K.A. Gunther, and C.T. Robbins. 2015. Balancing drift and flow: A genetic investigation of Greater Yellowstone Ecosystem (GYE) black bears. Molecular Ecology (submitted 5/10/2015).
  • Type: Journal Articles Status: Submitted Year Published: 2015 Citation: Rode, K.D., C.A. Stricker, J. Erlenbach, C.T. Robbins, A. Cutting, S. Jensen, S.D. Newsome, S.G. Cherry, G. Stenhouse, M. Brooks, A. Hash, and N. Nicassio: 2015. Isotopic incorporation and the effects of fasting and dietary lipid content on isotopic discrimination in large, carnivorous mammals. Physiological and Biochemical Zoology (submitted 4/15/2015).
  • Type: Journal Articles Status: Submitted Year Published: 2015 Citation: Mahalovich, M.F., M.J. Kimsey, J.K. Fortin, and C.T. Robbins. 2015. Isotopic heterogeneity in whitebark pine (Pinus albicaulis Englem.) nuts across geopgraphic, edaphic and climatic gradiets in the Northern Rockies (USA). Forest Ecology and Management (submitted 2/6/2015).
  • Type: Journal Articles Status: Submitted Year Published: 2015 Citation: Mugahid, D.A., T.G. Sengul, X. You, Y. Wang, L. Steil, N. Bergmann, M.H. Radke, M. Gesell-Salazar, C.T. Robbins, U. Volker, W. Chen, L. Nelson, and M. Gotthardt. 2015. Proteomic and transcriptomic changes in grizzly bears define mechanisms that protect against muscle atrophy. Nature (submitted 12/1/2014).
  • Type: Journal Articles Status: Awaiting Publication Year Published: 2015 Citation: Shine, C.L., S. Penberthy, C.T. Robbins, O.L. Nelson, and C.P. McGowan. 2015. Grizzly bear (Ursus arctos horribilis) locomotion: gaits and ground reaction forces. Journal of Experimental Biology (submitted 10/9/2014, revised 2/28/2015).
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Noel, M., J.R. Christensen, J. Spence, and C.T. Robbins. 2015. Using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to characterize copper, zinc and mercury along grizzly bear hair providing estimate of diet. Science of the Total Environment 529:1-9.
  • Type: Journal Articles Status: Accepted Year Published: 2015 Citation: Joyce-Zuniga N., R.C. Newberry, J. Ware, H.T. Jansen, C.T. Robbins, and O.L. Nelson. 2015. Positive reinforcement training for blood collection in grizzly bears (Ursus arctos horribilis) results in undetectable elevation in serum cortisol levels. Journal of Applied Animal Welfare Science (accepted 3/30/2015).
  • Type: Journal Articles Status: Awaiting Publication Year Published: 2015 Citation: Lopez-Alfaro, C., S.C.P. Coogan, C.T. Robbins, J.K. Fortin, and S.E. Nielsen. 2015. Assessing nutritional parameters of brown bear diets among ecosystems gives insight into differences among populations. PlosOne (in press 5/6/2015).
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Ripple, W.J., R.L. Beschta, J.K. Fortin, and C.T. Robbins. 2015. Wolves trigger a trophic cascade to berries as alternative food for grizzly bears. Journal of Animal Ecology 84:652-654.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Rode, K.D., C.T. Robbins, S.C. Amstrup, and O.L. Nelson. 2015. Can polar bears use terrestrial foods to offset lost ice-based hunting opportunities. Frontiers in Ecology and the Environment 13:138-145.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Nelson, O.L., and C.T. Robbins. 2015. Cardiovascular function in large to small hibernators: bears to ground squirrels. Journal of Comparative Physiology B 185:265-279.


Progress 10/01/13 to 09/30/14

Outputs
Target Audience: National Park Service and the general public. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Two (2)PhD students were produced. Ten (10) undergraduates assisted the PhD students. How have the results been disseminated to communities of interest? The results have been published in the scientific and non-scientific presses. What do you plan to do during the next reporting period to accomplish the goals? The Yellowstone project is complete. We will be moving to the new project in Katmai National Park.

Impacts
What was accomplished under these goals? Major insight has been provided for how Yellowstone grizzly bears are adapting to their changing environment.

Publications

  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Robu, M., J.K. Fortin, M.P. Richards, C.C. Schwartz, J. Wynn, C.T. Robbins, and E. Trinkaus. 2013. Isotopic evidence for dietary flexibility among European late Pleistocene cave bears (Ursus spelaeus). Canadian Journal of Zoology 91:227-234.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Teisberg, J.E., S.D. Farley, O.L. Nelson, G.V. Hilderbrand, M.J. Madel, P.A. Owen, J.A. Erlenbach, and C.T. Robbins. 2014. Immobilization of grizzly bears (Ursus arctos) with Dexmedetomidine, Tiletamine, and Zolazepam. Journal of Wildlife Diseases 50:74-83.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Erlenbach, J.A., K.D. Rode, D. Raubenheimer, and C.T. Robbins. 2014. Macronutrient optimization and energy maximization determine diets of brown bears. Journal of Mammalogy 95:160-168.


Progress 01/01/13 to 09/30/13

Outputs
Target Audience: Professional scientists and managers interested in the Yellowstone ecosystem Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Two PhD students were trained during the 4 years of this project. How have the results been disseminated to communities of interest? Numerous publications and scientific publications have originated from this work. What do you plan to do during the next reporting period to accomplish the goals? Continue to analyze data and publish.

Impacts
What was accomplished under these goals? We were able to generate extensive knowledge and understanding of the functional parameters of the Yellowstone ecosystem.

Publications

  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Fortin, J.K., C.C. Schwartz, K.A. Gunther, J.E. Teisberg, M.A. Haroldson, M.A. Evans, and C.T. Robbins. 2013. Dietary adjustability of grizzly bears and American black bears in Yellowstone National Park. Journal of Wildlife Management 77:270-281.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Middleton, A.D., T.A. Morrison, J.K. Fortin, C.T. Robbins, K.M. Proffitt, P.J. White, D. E. McWhirter, T.M. Koel, D. Brimeyer, W.S. Fairbanks, and M.J. Kauffman. 2013. Grizzly bear predation links the loss of native trout to the demography of migratory elk in Yellowstone. Proceedings of the Royal Society B 280: 1-8.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Fortin, J.K., J.V. Ware, H.T. Jansen, C.C. Schwartz, and C.T. Robbins. 2013. Temporal niche switching by grizzly bears but not American black bears in Yellowstone National Park. Journal of Mammalogy 94:833-844.
  • Type: Journal Articles Status: Accepted Year Published: 2014 Citation: Ripple, W.J., R.L. Beschta, J.K. Fortin, and C.T. Robbins. 2013. Trophic cascades from wolves to grizzly bears in Yellowstone. Journal of Animal Ecology 82: in press.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Schwartz, C.C., J.K. Fortin, M.A. J.E. Teisberg, M. A. Haroldson, C. Servhenn, C.T. Robbins, and F. Van Manen. 2014. Body and diet composition of sympatric black and grizzly bears in the Greater Yellowstone Ecosystem. Journal of Wildlife Management 77:1-11.
  • Type: Journal Articles Status: Awaiting Publication Year Published: 2014 Citation: Teisberg, J.E., M.A. Haroldson, C.C. Schwartz, K.A. Gunther, J.K. Fortin, and C.T. Robbins. 2014. Contrasting past and current numbers of bears visiting Yellowstone cutthroat trout streams. Journal of Wildlife Management 78: (in press, 11/8/2013).


Progress 01/01/12 to 12/31/12

Outputs
OUTPUTS: Grizzly bears (Ursus arctos) and American black bears (U. americanus) are sympatric in much of Yellowstone National Park. Three primary bear foods, cutthroat trout (Oncorhynchus clarki), whitebark pine (Pinus albicaulis) nuts, and elk (Cervus elaphus), have declined in recent years. Because park managers and the public are concerned about the impact created by reductions in these foods, we quantified bear diets to determine how bears living near Yellowstone Lake are adjusting. We estimated diets using: 1) stable isotope and mercury analyses of hair samples collected from captured bears and from hair collection sites established along cutthroat trout spawning streams and 2) visits to recent locations occupied by bears wearing Global Positioning System collars to identify signs of feeding behavior and to collect scats for macroscopic identification of residues. Approximately 45+/-22% (x+/-SD) of the assimilated nitrogen consumed by male grizzly bears, 38+/-20% by female grizzly bears, and 23+/-7% by male and female black bears came from animal matter. These assimilated dietary proportions for female grizzly bears were the same as 10 years earlier in the Lake area and 30 years earlier in the Greater Yellowstone Ecosystem. However, the proportion of meat in the assimilated diet of male grizzly bears decreased over both time frames. The estimated biomass of cutthroat trout consumed by grizzly bears and black bears declined 70% and 95%, respectively in the decade between 1997-2000 and 2007-2009. Grizzly bears killed an elk calf every 4.3+/-2.7 days and black bears every 8.0+/-4.0 days during June. Elk accounted for 84% of all ungulates consumed by both bear species. Whitebark pine nuts continue to be a primary food source for both grizzly bears and black bears when abundant, but are replaced by false-truffles (Rhizopogon spp.) in the diets of female grizzly bears and black bears when nut crops are minimal. Thus, both grizzly bears and black bears continue to adjust to changing resources, with larger grizzly bears continuing to occupy a more carnivorous niche than the smaller, more herbivorous black bear. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Wildlife managers, national park service biologists, wildlife scientists PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
The results of our study will be an important part of the judicial hearings on whether grizzly bears in the Yellowstone ecosystem will be delisted from their current threatened status and returned to state management.

Publications

  • Ware J.V., O.L.Nelson, C.T.Robbins, H.Jansen. 2012. Split parturition observed in a captive North American brown bear (Ursus arctos). Zoo Biology. 31:255-259.
  • Ware J.V., O.L.Nelson, C.T.Robbins, H.Jansen. 2012. Temporal organization of activity in the brown bear (Ursus arctos): Roles of circadian rhythms, light and food entrainment. American Journal of Physiology: Regulatory, Integrative and Comparative Physiology. 303:R890-R902.
  • Lin D., J.D.Hershey, J.S.Mattoon, C.T.Robbins. 2012. Skeletal muscles of hibernating brown bears are unusually resistent to effects of denervation. The Journal of Experimental Biology. 215:2081-2087.
  • Robbins C.T., M.Ben-David, J.K.Fortin, O.L.Nelson. 2012. Maternal condition determines maternal investment in newborn bear cubs. Journal of Mammalogy. 93:540-546.
  • Robbins C.T., C.Lopez-Alfaro, K.D.Rode, O.Toien, O.L.Nelson. 2012. Hibernation and seasonal fasting in bears: the energetic costs and consequences for polar bears. Journal of Mammalogy. 93:1493-1503.


Progress 01/01/11 to 12/31/11

Outputs
OUTPUTS: Grizzly bears (Ursus arctos) and black bears (Ursus americanus) are sympatric in much of Yellowstone National Park. The objective of the study was to understand the impact of recent changes in abundance of food sources on the interactions between grizzly and black bears. Three important food resources for bears in the park, cutthroat trout (Oncorhynchus clarki), whitebark pine nuts (Pinus albicaulis), and elk (Cervus elaphus), are declining due to processes partially initiated by humans. Hair samples were taken from grizzly and black bears upon trapping and locations for collared bears were visited. In addition, hair snares were placed on historical cutthroat trout spawning streams and individuals identified with DNA analysis. The importance of food items was estimated from GPS site visits, fecal screening, and stable isotope and mercury analysis of hair. The estimated number of cutthroat trout consumed by grizzly bears has declined from 20,910/year in the late 1980s, to 2,266/year in the late 1990s, to 332/year during this study (2006-2009). Ninety percent of female grizzly bears and 56% of male grizzly bears living in the vicinity of Yellowstone Lake consumed less than 5 kg of spawning cutthroat trout/annum. Our results suggest that for grizzly bears, much of that loss has been made up by feeding on neonatal elk. Approximately 45 plus/minus 22% of the assimilated nitrogen consumed by male grizzly bears, 38 plus/minus 20% for female grizzly bears, and 23 plus/minus 7% for male and female black bears came from animal matter. Although the mean estimate of dietary meat intake for male grizzly bears was less than an estimate from 1977-1996 (79 plus/minus 18%) and the mean for female grizzly bears was similar to an estimate from 1977-1996 (45 plus/minus 22%), neither was different (P less than 0.05) between time periods. These results indicate that the nutritional value of the various meat resources in the diets of Yellowstone grizzly and black bears for which Yellowstone is famous has remained relatively constant over the past 30 years. Elk accounted for 84% of all ungulates consumed and were the dominant ungulate used by both bear species. During September and October in years when whitebark pine nut production was minimal, black bears and female grizzly bears fed almost exclusively on false-truffles (Rhizopogon spp.). Thus, both grizzly bears and black bears continue to adapt to changing food resources, with larger grizzly bears continuing to occupy a more carnivorous niche than the smaller, more herbivorous black bear. Ongoing monitoring of both food resources and both bear species in Yellowstone National Park need to occur as bears continue to adapt to changes in food resources. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Results of the study will be involved in various court cases arising from the effort to delist (i.e., return to state management) grizzly bears in the Greater Yellowstone Ecosystem.

Publications

  • Lin, D., J.D. Hershey, J.S. Mattoon, and C.T. Robbins. 2011. Muscles of hibernating brown bears are unusually resistant to effects of denervation. Science.
  • Florin, S., L.A. Felicetti, and C.T. Robbins. 2011. The biological basis for understanding and predicting dietary-induced variation in nitrogen and sulfur isotope ratio discrimination. Functional Ecology. 25:519-526.
  • Gardi, J., O.L. Nelson, C.T. Robbins, E. Szentirmai, L. Kapas, and J. Krueger. 2011. Energy homeostasis regulatory peptides in hibernating grizzly bears. General and Comparative Endocrinology. 172:181-183.


Progress 01/01/10 to 12/31/10

Outputs
OUTPUTS: Grizzly bears (Ursus arctos) and black bears (Ursus americanus) are sympatric in much of Yellowstone National Park. Three important food resources for bears in the park, cutthroat trout (Oncorhynchus clarki), whitebark pine nuts (Pinus albicaulis), and elk (Cervus elaphus), are declining due to processes partially initiated by humans. The estimated number of cutthroat trout consumed by grizzly bears has declined from 20,910/year in the late 1980s, to 2,266/year in the late 1990s, to 332/year during this study (2006-2009). Ninety percent of female grizzly bears and 56% of male grizzly bears living in the vicinity of Yellowstone Lake consumed <5 kg of spawning cutthroat trout/annum. Our results suggest that for grizzly bears, much of that loss has been made up by feeding on neonatal elk. Approximately 45 +/- 22% (x- +/- SD) of the assimilated nitrogen consumed by male grizzly bears, 38 +/- 20% for female grizzly bears, and 23 +/- 7% for male and female black bears, came from animal matter. Although the mean estimate for male grizzly bears was less than an estimate from 1977-1996 (79 +/- 18%) and the mean female grizzly bears was similar to an estimate from 1977-1996 (45 +/- 22%), neither was significantly different (P < 0.05) between time periods. These results indicate that the importance of the various meat resources in the diets of bears for which Yellowstone is famous have remained relatively constant over the past 30 years. Elk accounted for 84% of all ungulates consumed and were the dominant ungulate used by both bear species. During September and October, in years when whitebark pine nut production was minimal, black bears and female grizzly bears fed almost exclusively on false truffles (Rhizopogon spp.). Thus, both grizzly bears and black bears continue to adapt to changing food resources, with larger grizzly bears continuing to occupy a more carnivorous niche than the smaller, more herbivorous black bear. Ongoing monitoring of both food resources and both bear species in Yellowstone National Park need to occur as bears continue to adapt to changes in food resources. PARTICIPANTS: Charles T. Robbins, PI; Laura Felicetti, Research Associate; Jennifer Fortin,PhD Student; Justin Teisberg, PhD Student; Scott Florin, MS Student TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Several manuscripts are currently being prepared and will be submitted for publication. These manuscripts will assist the park in understanding how the resident grizzly bears and black bears are adapting to changes in their environment.

Publications

  • Barrows, N.D., O.L. Nelson, C.T. Robbins, and B.C. Rourke. 2011. Increased cardiac alpha-myosin heavy chain in left atria and decreased myocardial insulin-like growth factor (IGF-I) expression accompany low heart rate in hibernating grizzly bears. Physiological and Biochemical Zoology 84(1): 1-17.
  • Florin, S.T., L.A. Felicetti, and C.T. Robbins. 2011. The biological basis for understanding and predicting dietary-induced variation in nitrogen and sulfur isotope ratio discrimination. Functional Ecology (In press).


Progress 01/01/09 to 12/31/09

Outputs
OUTPUTS: Bears were trapped around Yellowstone Lake, Yellowstone National Park (YNP) during the fall of 2006, the early summer and fall of both 2007 and 2008, and the early summer of 2009. Twenty-one grizzly bears (8 females and 13 males) and six male black bears have been captured and fitted with 27 individual Spread Spectrum Technology (SST) Geographic Positioning System (GPS) collars. During 2007 eight grizzlies (3 female and 5 male) and one black bear were tracked. That number increased to nine grizzlies (5 female and 4 male) and five black bears during the 2008 field season. Again in 2009 the number of bears tracked increased to 12 grizzlies (5 female and 7 male) and 4 black bears. Over the past three years we visited 3,846 GPS locations at which we collected 265 hair samples, 979 fecal samples, and forage samples. Bear sign (i.e. feeding, daybed, scat) was found at 2,671 of these sites. At 1,620 sites feeding was observed. The use of whitebark pine nuts, which are high energy, mirrored availability with use at 51, 4, and 148 sites, respectively, in 2007, 2008, and 2009 during which average cone counts per tree were 14.9, 8.6, and 46.5. Other food sources in high use when available were ungulates (primarily elk but some mule deer and bison), false-truffles, insects (primarily ants and yellow jackets), and berries. Forty-eight hair corrals were deployed on 35 streams on Yellowstone Lake that were historical cutthroat trout spawning streams. Hair corrals were visited bi-weekly from mid-May through mid-August during 2007, 2008, and 2009, during which 1,535 hair samples were collected. Stream surveys for spawning cutthroat trout were conducted in conjunction with hair snare visits. This project began in 2007 and each year we have seen an increase in the number of streams with spawners and in the maximum number of spawners seen on an individual stream. The first year spawning trout were only seen in ten streams, with the maximum number of spawners seen in one stream being five. The numbers increased in 2008 to fourteen streams with spawners and a maximum of 15 trout. In 2009, we saw spawners in 21 streams and up to 25 trout in any individual stream. Fry and/or fingerling counts were also observed and often estimated to be several hundred. Only one incident of fishing by bears was observed in the three-year study. Of the 1,535 hair samples collected at hair corrals over the three-year study, we sent 877 of these samples off for genetic analysis. 746 (85%) samples were assigned to individual bears using a suite of seven microsatellite loci (observed heterozygosity across seven loci: 0.672 for grizzlies and 0.650 for black bears). From this assignment, we now know at least 63 grizzly bears (42 male, 21 female) and 27 black bears (17 male, 10 female) visited tributary stream courses during this time. Of these, 8 male and 7 female black bears (15 in total; 56% of total number identified) and 12 male and 8 female grizzly bears (20 in total; 32% of total number identified) visited streams located near human development (front-country). Only 9 (18%) grizzly bears visited these areas during a period between 1997 and 2000 (Haroldson et al. 2005). PARTICIPANTS: Personnel from USGS, NPS, and Washington State University TARGET AUDIENCES: Park managers, bear scientists, and the general public PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
The study demonstrates that grizzly bears continue to occupy the Lake area within the Park even in the near absence of spawning cutthroat trout. The diversity of food resources (e.g., elk, vegetation, pine nuts, mushrooms) for bears in the Park is one of the strong points for continued occupancy even when important individual foods disappear.

Publications

  • McGowan, R.T.S., C.T. Robbins, J.R. Alldredge, and R.C. Newberry. 2009. Contrafreeloading in grizzly bears: implications for captive foraging enrichment. Zoo Biology: 28:1-19.
  • McGee-Lawrence, M.E., S.J. Wojda, L.N. Barlow, T.D. Drummer, A.B. Castillo, O. Kennedy, K.W. Condon, J. Auger, H.L. Black, O.L. Nelson, C. T. Robbins, and S.W. Donahue. 2009. Grizzly bears (Ursus arctos horribilis) and black bears (Ursus americanus) prevent trabecular bone loss during disuse (hibernation). Bone 45:1186-1191.
  • Robbins, C.T., L.A. Felicetti, and S.T. Florin. 2009. The impact of protein quality on stable nitrogen isotope ratio discrimination and assimilated diet estimation. Oecologia. 8 November 2009 (currently online and in press). http://www.ncbi.nlm.nih.gov/pubmedterm=Robbins+C.%5Bau%5D, http://www.citeulike.org/journal/springerlink-100425
  • Nelson, O.L., and C.T. Robbins. 2009. Cardiac function adaptations in hibernating grizzly bears (Ursus arctos horribilis). Journal of Comparative Physiology (currently online and in press).


Progress 01/01/08 to 12/31/08

Outputs
OUTPUTS: Trapping of grizzly bears around Yellowstone Lake in Yellowstone National Park continued during the early summer and fall of 2008. Nine grizzlies (five female and four male) and five black bears were captured and fitted with Spread Spectrum Technology (SST) Geographic Positioning System (GPS) collars. We visited 2,548 GPS locations in 2007 and 2008 at which we collected 139 hair samples, 488 fecal samples, as well as forage samples. The forty-eight hair snares deployed on 35 streams on Yellowstone Lake were visited bi-weekly from mid-May through mid-August during 2007 and 2008, at which time 1,180 hair samples were collected. Stream surveys for spawning cutthroat trout were conducted in conjunction with hair snare visits. Hair samples are being analyzed. 80% of the time of two PhD graduate students is spent on this project. PARTICIPANTS: Jennfier Fortin, Justin Teisberg, National Park Service TARGET AUDIENCES: State and federal wildlife and land management agencies, National Park Service PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Although it is still early in the study, it appears that grizzly bears have been able to replace the energy and nutrients that were once provided by cutthroat trout by preying on elk calves. However, there are limits to the availability of elk calves, so this may be a very temporary solution. Thus, it is increasingly important for the Park to continue in its efforts to remove lake trout and recover a healthy, abundant cutthroat trout population in Yellowstone Lake.

Publications

  • Nelson, O.L., C.T. Robbins, Y. Wu, and H. Granzier. 2008. Titin isoform switching is a major cardiac adaptive response in hibernating grizzly bears. American Journal of Physiology-Heart and Circulatory Physiology 295:H366-H371.
  • Hershey, J.D., C.T. Robbins, O.L. Nelson, and D.C. Lin. 2008. Minimal seasonal alterations in the skeletal muscle of captive brown bears. Physiological and Biochemical Zoology 81:138-147.
  • McGee, M.E., A.J. Maki, S.E. Johnson, O.L. Nelson, C.T. Robbins, and S.W. Donahue. 2008. Decreased bone turnover with balanced resorption and formation prevent cortical bone loss during disuse (hibernation) in grizzly bears (Ursus arctos horribilis). Bone 42:396-404.


Progress 01/01/07 to 12/31/07

Outputs
OUTPUTS: The first field season of data collection in the 3-year study occurred between May and October, 2007. Ten grizzly bears and one black bear were trapped around Yellowstone Lake and fitted with GPS collars. Field crews selected one/day per week for each bear and back-tracked the bear using hourly GPS locations to determine what the bear was doing at each location. During the spring, grizzly bears were apparently killing and consuming elk as a replacement for the loss of cutthroat trout. We have yet to determine if that is a lasting, worthwhile replacement for cutthroat trout. PARTICIPANTS: Jennifer Fortin, PhD candidate Justin Teisberg, MS candidate TARGET AUDIENCES: Managers of Yellowstone National Park General public

Impacts
The National Park Service is currently investing heavily in reducing Yellowstone Lake's lake trout population in order to recover a healthy cutthroat trout population. Cutthroat trout were historically an important spring/summer grizzly bear food. However, grizzly bears never consumed more than 1.5% of the cutthroat trout population when it was healthy. As the population is recovered, we will determine how grizzly bears respond to the return of cutthroat trout to their natal spawning streams.

Publications

  • Robbins, C.T., J.K.Fortin, K.D.Rode, S.D.Farley, and L.Shipley. 2007. Optimizing protein intake as a foraging strategy to maximize mass gain in an omnivore.. Oikos. 116:1675-1682.
  • Fortin, J.K., S.D.Farley, K.D.Rode, and C.T.Robbins. 2007. Dietary and spatial overlap amongst sympatric ursids relative to salmon use. Ursus : An Official Publication of the International Association for Bear Research and Management. 18:19-29.
  • Rode, K.D., S.D.Farley, C.T.Robbins, and J.K.Fortin. 2007. Nutritional consequences of experimentally introduced tourism in brown bears. The Journal of Wildlife Management. 71:929-939.


Progress 01/01/06 to 12/31/06

Outputs
This project is in the initial phases with the first field season starting summer 2007. As such, the past year has been spent in gaining necessary permits to trap grizzly bears around Yellowstone Lake and to provide housing for the field personnel, ordering GPS radiocollars, and doing preliminary studies to test the techniques that will be used. The study will last an additional 3 years.

Impacts
This project was rated #1 for funding within the western region of the USGS. The reason for the high rating is that it deals with 2 threatened species, grizzly bears and Yellowstone Lake cutthroat trout. Cutthroat trout are declining precipitously due to the unauthorized introduction of the more predatious lake trout, and cutthroat trout are a major spring/summer food of grizzly bears.

Publications

  • Donahue, S.W., M.E.McGee, K.B.Harvey, M.R.Vaughan, and C.T.Robbins. 2006. Hibernating bears as a model for preventing disuse osteoporosis. Journal of Biomechanics. 39:1480-1488.
  • Rode, K.D., S.D.Farley, and C.T.Robbins. 2006. Behavioral responses of brown bears mediate nutritional impacts of experimentally introduced tourism. Biological Conservation. 133:70-80.
  • Rode, K.D., S.D.Farley, and C.T.Robbins. 2006. Sexual dimorphism, reproductive strategy, and human activities determine resource use by brown bears. Ecology. 87:2636-2646.


Progress 01/01/05 to 12/31/05

Outputs
Cutthroat Trout in Yellowstone Lake are a threatened population due to the unauthorized introduction of Lake Trout. Cutthroat Trout populations are declining as the Lake Trout population is increasing. Because Cutthroat Trout are an important food resource for several dozen birds and mammals, the loss of Cutthroat Trout will detrimentally effect the Park's ecosystem. We have undertaken the current study to determine how the loss of Cutthroat Trout will effect grizzly bears. One of the methods that we will use quantifies the transfer of mercury between Cutthroat Trout and grizzly bears. Cutthroat trout contain relatively high levels of mercury. Grizzly bears consuming the trout deposit that mercury in their hair in proportion to the amount of trout consumed. Thus, we are using feeding studies with captive grizzly bears to determine relationships between the amount of Yellowstone Cutthroat Trout consumed and mercury levels in their hair. We will ultimately use these relationships to quantify the importance of Cutthroat Trout to the Park's bears by sampling their hair and quantifying the mercury concentration. We completed 10 feeding studies with captive grizzly bears during the past summer and are currently analyzing the fish, hair and blood samples

Impacts
Grizzly bears are the most charismatic mammal in Yellwstone National Park. Several million people visit Yellowstone each year hoping to see a grizzly bear. The potential loss of a major food supply for grizzly bears in that Park has national implications.

Publications

  • Robbins, C.T., L.A. Felicetti, and M. Sponheimer. 2005. The effect of dietary protein quality on nitrogen discrimination in birds and mammals. Oecologia 144:534-540.
  • Tollefson, T.N., C. Matt, J. Meehan, and C.T. Robbins. 2005. Quantifying spatiotemporal overlap of Alaskan brown bears and people. Journal of Wildlife Management 69:810-817.


Progress 01/01/04 to 12/31/04

Outputs
The main focus of this program has been in understanding the nutritional ecology of grizzly bears. The size, productivity, and density of grizzly bears in a population are primarily determined by the quantity and quality of their food resources. Thus, coastal salmon-feeding populations are denser and composed of large-bodied, highly productive bears as compared to interior, primarily herbivorous populations. While these relationships have been qualitatively understood for many years, their application to specific management issues has often been overlooked. For example, when important, high quality food resources are removed, adult bears that have grown much larger than the remaining food resources can support are guaranteed to become problem bears. The real world, case examples are when open-pit garbage dumps are closed or salmon populations suddenly decline. Bears that have grown large consuming these foods can not revert to lesser foods as their large body size requires much higher daily energy intake than the smaller bears that would normally feed on the lesser foods. Thus, a segment of the population will come into conflict with people and will have to either be moved to areas where those foods are still available or be killed. We are also examining how bears respond to people in different ecosystems. One popular myth about grizzly bears is that they actively hunt people. In order to determine the response of individual bears to people, we have placed GPS collars on grizzly bears in Alaskan wildernesses and purposefully had people walk through their home ranges. Grizzly bears in areas where hunting (both legal and illegal) is common flee from people, frequently vacating the area for several days even after the people have left. Thus, they very actively avoid people.

Impacts
Our efforts continue to affect the management of grizzly bears and therefore natural resources in the West. Our results indicate that (1) Yellowstone National Park should continue to control lake trout in Yellowstone Lake for the benefit of cutthroat trout and closely monitor the health of the whitebark pine forests as cutthroat trout and whitebark pine nuts are two major foods for grizzly bears in that Park and (2) Alaska should continue to manage salmon as an important food resource for both aquatic and terrestrial ecosystems. Losses of any of these major food resources would be a major blow to the perpetuation of grizzly bears in the West.

Publications

  • Felicetti, L.A., R.O. Rye, C.C. Schwartz, M.A. Haroldson, K.A. Gunther, L. Waits, and C.T. Robbins. 2004. Use of naturally occurring mercury to determine the importance of cutthroat trout to Yellowstone grizzly bears. Canadian Journal of Zoology 82:493-501.
  • Robbins, C.T., C.C. Schwartz, and L.A. Felicetti. 2004. Nutritional ecology of ursids: A review of newer methods and management implications. Ursus 15:161-171.
  • Hilderbrand, G.V., S.D. Farley, C.C. Schwartz, and C.T. Robbins. 2004. Importance of salmon to wildlife: Implications for integrated management. Ursus 15:1-9.


Progress 01/01/03 to 12/31/03

Outputs
We continue to progress in understanding the nutritional ecology of grizzly bears. We just completed a study of the nutritional importance of two major grizzly bear food resources in the Yellowstone ecosystem. Both food resources are in decline. Cutthroat trout, that are being extirpated by lake trout, are an important food resource for male grizzly bears that live around Yellowstone Lake. The other imperiled food resource, whitebark pine nuts, are the single most important food for female grizzly bears. Variation in cub production is directly related to the annual nut crop. During good years of mast production, pine nuts provide as much as 90% of the food for over 80% of the resident grizzly bear population. Additional ongoing studies include understanding the interaction of bears, ecotourists, and salmon in the wilds of Alaska. We've also started several projects to understand the physiology of hibernation in grizzly bears with potential implications to human, pet, or livestock medical care.

Impacts
Our efforts continue to affect the management of grizzly bears and therefore natural resources in the West. Our results indicate that Yellowstone National Park should continue to control the lake trout population and closely monitor the health of the whitebark pine forests. Loss of the latter would be a major blow to the health of the grizzly bear population in Yellowstone.

Publications

  • Felicetti, L.A., C.T. Robbins, and L.A. Shipley. 2003. Dietary protein content alters energy expenditure and composition of the gain in grizzly bears (Ursus arctos horribilis). Physiological and Biochemical Zoology 76:256-261.
  • Felicetti, L.A., R.O. Rye, C.C. Schwartz, M.A. Haroldson, K.A. Gunther, D. L. Phillips, and C.T. Robbins. 2003. Use of sulfur and nitrogen stable isotopes to determine the importance of whitebark pine nuts to Yellowstone grizzly bears. Canadian Journal of Zoology 81:763-770.
  • Nelson, O.L., M-M. McEwen, C.T. Robbins, L.A. Felicetti, and W.F. Christensen. 2003. Cardiac function in active and hibernating grizzly bears. Journal of the American Veterinary Medical Association 223:1170-1175.


Progress 01/01/02 to 12/31/02

Outputs
The importance of foods to Yellowstone grizzly bears was quantified during the past year. Up to half of nourishment for the +/-600 grizzly bears in Yellowstone comes from whitebark pine nuts in years of good crops. When pine nuts are not available, meat (elk, bison, ants, army cutworm moths, and cutthroat trout) become much more important.

Impacts
Many of the most important foods consumed by grizzly bears in Yellowstone are threatened. For example, whitebark pines are threatened by an exotic fungus that has killed 50 to 100% of the trees in other areas. Such threats pose major, longterm problems for management of grizzly bears in Yellowstone National Park.

Publications

  • Robbins, C.T., G.V. Hilderbrand, and S.D. Farley. 2002. Incorporating concentration dependence in stable isotope mixing models: A response to Phillips and Koch (2002). Oecologia 133:10-13.


Progress 01/01/01 to 12/31/01

Outputs
The nutritional ecology of grizzly bears in western North America, from Yellowstone to northern Alaska, was studied. The overall theme of the studies was to determine the relative importance of salmon, vegetation, ungulates, & berries to the nutritional well-being of individual bears & subsequently their populations. Grizzly bears that must consume vegetation and berries with minimal access to significant meat resources, such as large ungulates or salmon, will be relatively small bears having low reproductive rates & densities. Bears with access to abundant salmon will be over twice as large & have densities that are up to 50 times greater. In consuming salmon, bears also perform a vital function for Northwest riparian forests by completing the cycle of nutrient flow from marine to terrestrial ecosystems. Salmon traditionally moved hundreds of tons of nitrogen, phosphorus, & other essential nutrients from the oceans into Northwest rivers. Bears were then the predominant transporter of those nutrients from the rivers into the terrestrial environment via their urine, feces, and decaying salmon that were removed from the streams but not consumed. By using stable isotopes, we determined that approximately 20% of the nitrogen in spruce trees growing along major Alaskan salmon streams originated in salmon, & approximately 80% of that nitrogen passed through a bear before being taken up by the tree. Forests that receive this nutrient input are more productive, provide more diverse stream spawning habitat, & thus ultimately benefit future generations of salmon. Thus, the management of salmon, bears & Northwest forests can be viewed as a synergistic unit.

Impacts
The WSU bear nutrition studies continue to be of interest to Pacific Northwest agencies responsible for land and wildlife management decisions. WSU bear studies are currently being funded by agencies managing Yellowstone National Park and large tracts of Alaskan wilderness. The bear/salmon/forest nutrient transfer studies have been widely discussed in newspaper and magazine articles.

Publications

  • Hilderbrand, G.V., C.C. Schwartz, C.T. Robbins, M.E. Jacoby, T.A. Hanley, S.M. Arthur, and C. Servheen. 1999. Importance of meat, particularly salmon, to body size, population productivity and conservation of North American brown bears. Can. J. Zool. 77:132-138.
  • Jacoby, M.E., G.V. Hilderbrand, C. Servheen, C.C. Schwartz, S.M. Arthur, T.A. Hanley, C.T. Robbins, and R. Michener. 1999. Trophic relations of brown and black bears in several western North American ecosystems. J. Wildl. Manage. 63:921-929.
  • Hilderbrand, G.V., C.T. Robbins, and S.D. Farley. 1999. Response to Bocherens comments on "Use of stable isotopes to determine diets of living and extinct bears." Can. J. Zool. 76:2301-2303.
  • Hilderbrand, G.V., S.G. Jenkins, C.C. Schwartz, T.A. Hanley, and C.T. Robbins. 1999. Effect of seasonal differences in dietary meat intake on changes in body mass and composition in wild and captive brown bears. Can. J. Zool. 77:1623-1630.
  • Hilderbrand, G.V., T.A. Hanley, C.T. Robbins, and C.C. Schwartz. 1999. Role of brown bears (Ursus arctos) in the flow of marine nitrogen into a terrestral ecosystem. Oecologia 121:546-550.
  • Partridge, S.T., D.L. Nolte, G.J. Ziegltrum, and C.T. Robbins. 2000. Impacts of supplemental feeding on the nutritional ecology of black bears. J. Wildl. Manage. 65;191-199.
  • Felicetti, L.A., L.A. Shipley, G. Witmer, and C.T. Robbins. 2000. Digestive strategies of North American porcupines: Nitrogen, dry matter, and energy digestibility of natural forages. Biochemical and Physiological Zoology 73:772-780.
  • Rode, K.D., C.T. Robbins, and L.A. Shipley. 2001. Constraints on herbivory by grizzly bears. Oecologia 128:62-71.
  • Jenkins, S.G., S.T. Partridge, T.R. Stephenson, S.D. Farley, and C.T. Robbins. 2001. Nitrogen and carbon isotope fractionation between mothers, neonates, and nursing offspring. Oecologia 129:336-341.


Progress 01/01/00 to 12/31/00

Outputs
We continue to study the nutritional ecology of bears. Much of the grizzly work focuses on the importance of salmon to bears; and if salmon are not available, the value of vegetation as an alternate food resource. Our earlier work indicated that an average adult female consumes over 3000 lbs of salmon, but transfers over 90% of the salmon's nitrogen to the terrestrial ecosystem. Thus, using isotope technology, we determined that 15 to 25% of the nitrogen in spruce trees is of salmon origin where healthy grizzly bear populations occur, and that 80% of that nitrogen passed through grizzly bears. We are currently involved in a follow up study in Olympic National Park where we are attempting to use the isotope record in tree rings to quantify the historical and current role of salmon in those ecosystems.

Impacts
Our grizzly/salmon research results have been widely disseminated by the popular press. Stories have appeared in: 1. American Rivers, February 2000 2. Christian Science Monitor, February 2000 3. National Geographic World, October 2000 4. Article pending the Portland Oregonian 5. Article pending in National Geographic 6. Article pending in Wildlife Conservation, New York Zoological Society.

Publications

  • Hilderbrand,G.V., C.C.Schwartz, C.T. Robbins, and T.A.Hanley. 2000. Effect of hibernation and reproductive status on body mass and condition of coastal brown bears. J. Wildl. Manage. 64:178-183.
  • Rode K.D. and C.T.Robbins. 2000. Why bears consume mixed diets during fruit abundance. Can. J. Zool. 78:1640-1645.
  • Rominger E.M., C.T.Robbins, M.A.Evans, and D.J. Pierce. 2000. Autumn foraging dynamics of woodland caribou in experimentally manipulated habitats, Northeastern Washington, USA. J. Wildl. Manage. 64:160-167.


Progress 01/01/99 to 12/31/99

Outputs
We continued to examine the nutritional & foraging ecology of grizzly bears. Studies that have been recently completed include determining 1) importance of salmon to coastal grizzly bears in southern Alaska, 2) role that grizzly bears play in fertilizing the riparian plant community with nutrients, such as nitrogen & phosphorus, that they have consumed from salmon, & 3) value of herbaceous vegetation in the diet of grizzly bears. Salmon are extraordinarily important to bears. Populations that have access to abundant salmon are as much as 50 times denser than less well-nourished populations. Bears that consume salmon are an important link between the marine nutrients in salmon & riparian forests. As omnivores, bears can also do well on early season, nutritious forbs & grasses. Thus, there are many opportunities to improve the well-being of wild bear populations by improving their food resources.

Impacts
(N/A)

Publications

  • Hilderbrand, G.V., C.C. Schwartz, C.T. Robbins, M.E. Jacoby, T.A. Hanley, S.M. Arthur, and C. Servheen. 1999. Importance of meat, particularly salmon, to body size, population productivity and conservation of North American brown bears. Can. J. Zool. 77:132-138.
  • Hilderbrand, G.V., C.T. Robbins, and S.D. Farley. 1999. Response to Bocherens comments on "Use of stable isotopes to determine diets of living and extinct bears." Can. J. Zool. 76:2301-2303.
  • Hilderbrand, G.V., T.A. Hanley, C.T. Robbins, and C.C. Schwartz. 1999. Role of brown bears in the flow of marine nitrogen into a terrestrial ecosystem. Oecologia 121:546-550.
  • Jacoby, M.E., G.V. Hilderbrand, C. Servheen, C.C. Schwartz, S. M. Arthur, T.A. Hanley, C.T. Robbins, and R. Michener. 1999. Trophic relations of brown and black bears in several western North American ecosystems. J. Wildl. Manage. 63:921-929.
  • Parker, K.L., M.P. Gillingham, T.A. Hanley, and C.T. Robbins. 1999. Energy and protein balance of free-ranging black-tailed deer in a natural forest environment. Wildl. Monogr. 143:48pp.


Progress 01/01/98 to 12/31/98

Outputs
Most of the effort during the past year focused on studying the 1) interaction of salmon, brown bears, and forests in coastal Alaska, and 2) the trophic relations of brown and black bears in Yellowstone National Park, Glacier National Park, and several other western ecosystems. Adult body weights, productivity, and population density of brown bears are highly correlated to dietary meat content. Interior, low meat populations like those bears in Denali or Glacier National Park occur at 1/50th the density of several Alaskan, salmon-feeding populations. Adult female brown bears on the Kenai Peninsula where abundant spawning runs of salmon occur consume about 2200 pounds of salmon per year. These and other observations have been summarized in the following manuscripts:

Impacts
(N/A)

Publications

  • Hilderbrand, G., Farley, S. and Robbins, C. 1998. Predicting body condition of bears via two field methods. J. Wildl. Manage. 62:406-409.
  • Barboza, P., Garley, S. and Robbins, C. 1998. Whole-body urea cycling and protein turnover during hyperphagia and dormancy in growing bears (Ursus americanus and U. arctos). Can. J. Zool. 75:2129-2136.


Progress 01/01/97 to 12/31/97

Outputs
We have been able to develop a new, high-fiber diet for captive moose that shows promise in reducing the incidence of inflammatory bowel disease. The diet incorporates agricultural waste residues, such as citrus pulp, that the moose appear to tolerate quite well. We are currently conducting growth trials to determine if the new diet can adequately meet all nutritional requirements. The bear research program also had a good year in that 45 bears were handled during the three capture sessions on the Kenai Peninsula of Alaska. Each bear was fitted with a GPS collar so the bears location was determined continuously by satellite positioning. Based on a combination of feeding trials using captive bears and weight gain data for the wild bears, we estimated that the population of approximately 300 bears is consuming about 900,000 pounds of salmon during the three month spawning season. Thus, the bears depend heavily on salmon to meet their yearly nutritional needs.

Impacts
(N/A)

Publications

  • Farley, S.D. and C.T. Robbins. 1997. Validation of 22sodium to estimate food intake of bears. J. Wildl. Manage. 61:52-56.
  • Welch, C.A., J. Keay, K.C. Kendall, and C.T. Robbins. 1997. Constraints on frugivory by bears. Ecology 78: 1105-1119.