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Radiotelemetry was used to locate 101 grizzly bear (Ursus arctos) dens from 1975 to 1980; 35 dens were examined on the ground. Pregnant females denned in late October, and most other bears denned by mid-November. Duration of denning averaged 113, 132, and 170 days for males, females, and females with new cubs, respectively. Males emerged from mid-February to late March, followed by single females and females with yearlings and 2-yearolds. Females with new cubs emerged from early to mid-April. Den sites were associated with moderate tree cover (26%-75% canopy cover) on 30?-60? slopes. Dens occurred on all aspects, although northerly exposures were most common. Grizzly bears usually dug new dens but occasionally used natural cavities or a den from a previous year. Males usually dug larger dens than females with young. Eight excavated and 2 natural dens of the 35 examined dens were used for more than 1 year. Int. Conf Bear Res. and Manage. 6:111-117 The Interagency Grizzly Bear Study Team has studied grizzly bears in and around Yellowstone Na? tional Park since 1973. One major objective was to identify grizzly bear habitat requirements. Grizzly bears occupy dens in the Yellowstone area for up to 6 months of each year and dens are therefore an important segment of the habitat. Intelligent man? agement decisions depend on knowing dates of den entry and emergence, general areas of denning, and site selection. We gathered data pertaining to these factors from fall 1975 through 1980. Craighead and Craighead (1972) did the original work on grizzly bear dens and denning habits in this area between 1963 and 1968. Since the completion of those studies, the Yellowstone grizzly bear pop? ulation has dispersed considerably because garbage dumps within the park have closed (Judd and Knight 1980). We acknowledge the assistance of many seasonal employees in investigating den sites, especially D. Burrup, L. Cayot, C. Hancock, C. Hunt, and H. Ihsle. M. Duffy piloted the helicopter when we marked den sites, and D. and R. Stradley piloted the planes used to gather data on den locations and denning and emergence dates. J. Beecham reviewed this manu? script.

A 5-year double-blind test was conducted to test the predictive capability ofa previously published (Picton 1978) regression (Y =2.01 + 0.042*), which described the relationship between the litter size of grizzly bears (Ursus arctos horribilis) and an index of climate plus carrion availability (climatecarrion index). This regression showed an efficiency in excess of 99% in predicting the observed grizzly bear litter size. The predictions made using the climate-carrion index had a mean absolute error of less than 25% of forecasts using other methods. The updated climate-carrion index regression, which includes all of the 16 years for which data are available, is Y = 2.009 + 0.042.x (r = 0.78; P < 0.01; N = 16). We concluded that the climate-carrion index can be a helpful tool in predicting grizzly bear litter size. The relation of this information to the effects of the closure of Yellowstone Park garbage dumps is discussed. Int. Conf Bear Res. and Manage. 6:41-44 The prospect of a carbon dioxide induced climate change (Hansen et al. 1981) has increased the need to sharpen the tools of predictive ecology. Effective tools would make it possible to develop and take corrective management actions before the Yellow? stone grizzly bear population is severely affected by the new climate regime. Evidence for such a climate change has been increasing, and it will likely consti? tute the major environmental impact of the next 50 years (Dickinson and Cicerone 1986). The impact of such climate changes increases as one moves toward the poles. Therefore the climate impact at the latitude of Yellowstone National Park would be more severe than the global average (Kellogg and Schware 1981). This study represents a test of the predictive ability ofa regression (Picton 1978) relating the mean litter size of grizzly bears observed during the summer in Yellowstone National Park to a modified Lamb cli? mate index (1963) which includes precipitation and temperature covering the previous October to May period. This project was supported by the Interagency Grizzly Bear Study Team and the Mont. Agric. Exp. Sta. (Journal Series 1374).

Thirty-seven grizzly bears (Ursus arctos) equipped with radio transmitters were monitored in and around Yellowstone National Park between 1974 and 1979. Ten of the bears were known or suspected to kill livestock; 3 preyed on cattle, 6 on sheep, and 1 on both. Bears that killed livestock ranged widely in and out of Yellowstone Park and normally exhibited foraging habits similar to those of other bears. All subadult and adult bears known to have the opportunity killed sheep. Most bears that came into contact with cattle did not make kills. All known cattle killers were adult bears, while 4 sheep killers were subadults. Sheep grazing should be reduced as much as possible on grizzly range, and cattle grazing allowed only if owners are willing to absorb predation losses. Int. Conf Bear Res. and Manage. 5:186-190 Investigations of grizzly bear ecology in and around Yellowstone National Park were begun by an interagency team in 1973. The relationship between grizzly bears and livestock on national forests was investigated as a subproject during the years 1975-1979. Information on grizzly bear-livestock relation? ships was scarce. Hubbard and Harris (1960) published a popular account of historical inci? dents. Sarber (unpubl. rep., Alaska Coop. Wildl. Res. Unit, 1939) investigated cases of bears preying on cattle and found that many cattle died of other causes. Eide (1965) concluded that brown bears were an effective predator on cattle on Ko? diak Island. Murie (1948) documented cases of grizzly bear predation on cattle in the southern portion of our study area and expressed concern about the effects of a general predator control policy on the grizzly bear population. Data on movements and home ranges of the Yellowstone grizzly showed that they are very mobile and range widely throughout Yellowstone National Park and surrounding forests (Craighead 1980, Knight et al., 1976 Annual Rep. Interagen? cy Study Team, Yellowstone grizzly bear investi? gations, 1977, Blanchard and Knight 1980). If, as a result of this mobility, bears were killing livestock and in return being killed by stockmen, the entire population could be affected. This pa? per reports our findings on grizzly bear-livestock relationships. The study area centered around Yellowstone National Park and included portions of Wyoming, Idaho, and Montana. Some of this area outside 1 Present address: Colville Confederated Tribes, P.O. Box 150, Nespelem, WA 99155. of the park was subjected to livestock grazing (Fig. 1). A complete description of the vegeta? tion and physiography of the area was given by Knight et al. (1976 Annual Rep. Interagency Study Team, Yellowstone grizzly bear investiga? tions, 1977). We wish to acknowledge the assis? tance of Mr. Ross Davis and Mr. William Enget, both sheepmen from St. Anthony, Idaho. Sever? al sheepherders and cattle association riders con? tributed information and assistance, although sometimes unwittingly. Personnel of the Bridger Teton, Gallatin, Shoshone, and Targhee National Forests were cooperative and gave assistance when needed. Mr. Tom Toman, Wyoming Game and Fish Commission, was very cooperative as were all personnel from the State University, and Mr. Randall Hall, Supervisor, Shoshone National Forest, have reviewed the manuscript.