Terry Larsen, Anja Sorensen, Sarah Rovang, and Gordon B. Stenhouse, Foothills Research Institute Grizzly Bear Program
Mathieu Bourbonnais, Spatial Pattern Analysis and Research (SPAR) lab, University of Victoria
June 2015
Executive Summary
The grizzly bear has been deemed a threated species in Alberta due to lower than expected population size and because of ongoing human recreational and industrial activities occurring within grizzly bear range. Despite a moratorium on hunting (2006) and a recovery plan (2008), grizzly bears along the eastern slopes of Alberta continue to experience high levels of human caused mortality. As human activities continue to grow and expand, particularly within core grizzly bear conservation areas, new approaches to land use management and planning are needed to effectively maintain habitat conditions (security, food supply) in a state that would promote recovery.
This project began in 2013 following discussions between the Foothills Research Institute (fRI) Grizzly Bear Program and Weyerhaeuser (Drayton Valley) regarding planned forest harvesting operations occurring within core grizzly bear conservation areas. Weyerhaeuser was interested in understanding more about the current population status and space use patterns of grizzly bears in a portion (three watershed units) of their Drayton Valley FMA, where new approaches to both harvest design and access management had been proposed. As this work moved forward, West Fraser (Hinton, Edson, and Sundre) and other fRI partners (Alberta Environment and Parks) became interested in this project. Therefore, the 2013 study area expanded to include the entirety of the Yellowhead Population Unit (BMA 3) and the research plan was modified to meet the information needs of our partners.
This project moves beyond what is currently known about grizzly bear response to forest harvesting as we aim to investigate changes in response over longer time frames using historic (1999 – 2003) and current data. At this time, the evaluation of newly suggested harvesting prescriptions have not been evaluated relative to bear behavior or numerical response of the population. This research effort provides a valuable opportunity to assist Alberta’s forestry sector in understanding how their management activities can be better integrated with the ecological needs of grizzly bears and assist in provincial grizzly bear recovery efforts.
The work presented in this report aims to improve our understanding of grizzly bear distribution and abundance, habitat use, and movement patterns within three watershed units that encompasses core grizzly bear recovery zones, which are managed by Weyerhaeuser and West Fraser forest companies. The findings contained within this is report is based on the first two years of data collected in this longer term research project and should be seen as an interim report.
In section 6 (Distribution and abundance of grizzly bears in the Pembina study area), we assessed change in the distribution and abundance of grizzly bears by comparing the results of DNA hair snag inventory work conducted within BMA 3. Our comparisons included 46 common cells (7 x 7 km) from three projects (2004, 2013, and 2014) that overlapped with the Pembina Study area. The results of our genetic analysis identified 4, 16, and 7 unique bears in 2004, 2013, and 2014, respectively. This finding suggests an increase in the local grizzly bear population from 2004. Comparisons of the 2004 and 2014 data showed of the 46 cells sampled, 63% showed no change in the number of unique bears, 17% increased, and 20% decreased. From 2004 to 2014, there appeared to be an eastward shift in bear distribution. Although the mechanism(s) influencing observed changes in bear distribution and abundance are not known, future modeling work will evaluate correlations associated with changes in habitat conditions (mortality risk, food supply) as well as alternative management actions such as long distance relocations of problem bears.
In section 7 (Grizzly bear response to roads when using forestry cutblocks: does proximity and density of road types influence habitat selection?), we evaluated seasonal response of male and female grizzly bears to different road types (main/secondary, tertiary, decommissioned/reclaimed) using a long-term GPS location data set (1999-2014). We compared responses of the population (all bears) to those captured specifically for this project (Pembina bears). Individual and population level resource selection function models revealed similar responses between all bears and the Pembina bears; grizzly bears avoided main/secondary roads, exhibited variable responses (positive and negative) towards tertiary and decommissioned/reclaimed roads, and avoided areas of relatively high road density. Our findings suggest that new approaches to forest management where roads are decommissioned or reclaimed are likely to benefit grizzly bears. Attempts should attempt to increase the distance cutblocks are from roads and minimize road density, particularly tertiary roads that account for the relatively high density of roads observed in this study. Other approaches to access management such as the use of gates could also benefit grizzly bears, but needs to be tested empirically.
In section 8 (Exploring relationships among roads, forest harvest blocks and grizzly bear movement), we assessed grizzly bear movements in relation to disturbance features including forestry cutblock and roads. We used GPS location data from male and female grizzly bears collected between 2013 and 2014 to determine specific factors that influence movement (step length) in the vicinity of cutblocks and roads. Step lengths are commonly used in wildlife movement models with short steps indicative of foraging or search behaviour, whereas long steps represent “exploratory” movement behaviour. We used generalised additive models (GAM) to determine the influence of road type, age (years since disturbance), and density as well as forest harvest block age, area (km2), perimeter length (km), and area to perimeter ratio. Gender, time of day (day vs. night) and season were also included as predictor variables. Our main findings suggested that gender based differences in step length were negligible. Step lengths in relation to roads tended to be longer as road proximity and density increased. Conversely, step lengths in relation to cutblocks tended to be shorter as proximity and density increased. Our findings support our contention that bears are using forestry cutblocks primarily for foraging, whereas roads could be used for both foraging and exploratory movements. Access management is essential to ensure high quality foraging habitat such as forestry cutblocks do not result in mortality events associated with roads.