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Effects of resource extraction industries on behaviour and population dynamics of grizzly bears in the Flathead drainage, British Columbia and Montana

University of British Columbia

The range and numbers of grizzly bears (Ursus arctos L.) have been greatly reduced since Europeans settled North America and there is concern that various human activities threaten many of the remaining bears. In this thesis I examine relationships between resource extraction industries and grizzly bear ecology, behaviour, and population dynamics in an area undergoing timber harvest and gas exploration. The major hypothesis investigated was that the industrial activities in the study area would be detrimental to the grizzly population and I predicted either a low density of bears compared to other interior populations, or at least a negative rate of increase. To determine specific causes for any observed population response, I monitored behavioural reactions of grizzly bears to industrial activities and habitats modified by these activities. The selection of seasonal home ranges and use of habitat components, elevation, and aspects by grizzly bears from these ranges are presented. Based on 4872 relocations of 55 radio-collared bears over a 9 year period, grizzlies were found to generally follow 1 of 2 seasonal home range selection strategies. Mountain resident (MR) bears remained in mountainous terrain for the entire year while elevational migrating (EM) bears moved down to the Flathead Valley bottom twice each year. Habitats frequently used by bears were low elevation riparian areas, snowchutes, high elevation burns, and low elevation timber and open timber. Cutting units were rarely used. Most bears used habitats within 100 m of roads less than expected, resulting in an effective habitat loss of 8.7%. Avoidance of roads was independent of traffic volume, suggesting that only a small number of vehicles is sufficient to displace bears. However, roads and nearby areas avoided by bears during day were used at night. Yearlings and females with cubs used habitats near roads more than other bears. Five comparisons of bear use before, during, and after industrial activity indicated little displacement. Because the estimated average density of grizzly bears was 6.4/100km², which was high for an interior population, and their estimated rate of increase was positive (r[sub s] = 0.081), the major hypothesis was rejected. Resource extraction industries did contribute to grizzly bear mortality indirectly, however, by making roads which provide easy access to hunters, poachers and settlers. Of the 9 grizzlies which died when radio-collared, 2 were killed by legal hunting, 5 were illegally killed; 3 of these illegal kills occurred in 4% of the study area with permanent human settlement. Vehicular access planning and post-operational control are major recommendations of this study.

Text

2010-10-16

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http://hdl.handle.net/2429/29212

Animal Science

University of British Columbia

Graduate