UBC Theses and Dissertations
Activity measures of free-ranging grizzly bears (Ursus arctos) in the Flathead drainage McCann, Robert Keith
Between 1984 and 1988, 4756 hours of activity data were collected on 15 different grizzly bears (Ursus arctos) in the Flathead drainage of southeastern British Columbia and adjacent portions of Montana. Data were collected with the aid of portable chart recorders that recorded the output from motion-sensitive radio collars. While many benefits stem from remote sensing of a study animal as intractable as the grizzly, both the method of data collection and the assumptions employed in translating chart recordings into quantitative measures of bear activity may affect conclusions drawn. Major objectives of this study were: 1) to assess the validity of procedures employed to translate continuous chart recordings of signal patterns from motion-sensitive radio collars into quantitative measures of bear activity; 2) to assess whether active and inactive bout lengths were related to sex and age related differences in energetic requirements and seasonal differences in food type; and 3) to document activity budgets and patterns as functions of sex, age, season, and the daily solar cycle. In the absence of concurrent visual observations of grizzly bears and recorded signal patterns, the validity of procedures used to interpret chart recordings was assessed by estimating percent of time active (%TA) under varying definitions of active and inactive bouts, and by comparing %TA to values found by other researchers. Estimates of %TA were stable over the range of activity bout definitions examined. Stability resulted from bears spending most of their time in active and inactive bouts > 30 min duration. Estimates of %TA for this study agreed with results on other populations. Over the non-denning portion of the year, grizzly bears were active about 55% of the time. Analyses of bout durations were plagued by a bias against active bouts to be monitored in their entirety, because when active, bears frequently moved out of range of the chart recorder. The distribution of activity over the 24-hour cycle differed from many other studies in that bears in the Flathead were active mostly in daylight hours. A greater use of darkness by bears in the fall, compared to other seasons, may be related to available daylight or to avoidance of hunters. While activity patterns were generally bimodal with activity peaks in morning and evening, the morning activity peak was not strongly tied to sunrise. Activity in the morning generally reached a peak 1 or more hours after sunrise. Seasonal trends in activity budgets conformed to physiological changes in bears necessitated by requirements for denning. Significant individual variation exists in both activity patterns and budgets, and may be related to body size, to frequency dependent foraging strategies, or to differing competitive ability for defendable resources among sex-age classes of bears.
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