Ecological relationships between grizzly bears and forest management in the Coast-Interior transition of British Columbia


Increasing the knowledge and information available on the grizzly bear populations and habitats in the Lillooet area is key to creating better resource management decisions. Grizzly bears are rare in this area and these Grizzly Bear Population Units are classified as Threatened. Gathering information on abundance, distribution, and habitat use in the St’at’imc Nation Territory is essential for improving our understanding of these Threatened bear populations. This summary outlines the results of the first three years of a multi-year, multi-partner grizzly bear study. The project was also designed to evaluate the impacts of development and other human influences on grizzly bear habitat selection, movement and population trends.

Project results will be used to revise forest management practices and create habitat restoration plans in the Bridge River area where applicable.

Background of the research project

Lillooet Grizzly Bear Working Group’s mission statement is:

Empowering local people to participate in grizzly bear population recovery and habitat conservation within the Lillooet area to ensure viable and healthy grizzly bear populations and habitats across their natural ranges.

There are five project objectives aimed at developing greater certainty in planning and decision making; promoting more effective forestry management to positively affect grizzly habitat and conservation; examining historical information to aid population recovery target setting and developing guidelines and information that will be useful in similar efforts across the coastal-interior transition in southern BC.

This project was funded, supported and provided with in-kind contributions by:

  • Upper St’at’imc Language, Culture and Education Society
  • Lillooet Tribal Council
  • Lillooet TSA Association
  • BC Hydro Bridge Coastal Fish and Wildlife Restoration Program
  • Habitat Conservation Trust Fund
  • Ministry of Environment
  • Ministry of Forests
  • Squamish-Lillooet Regional District
  • Bridge River Lillooet Newspaper
  • St’at’imc Runner Newspaper

Methods and Materials / Study area

In spring, 2005, 2006 and 2007, grizzly bears were captured, and GPS collars were placed on them. The bears were then monitored by air using a Cessna 337. These flights were conducted to download GPS locations approximately every two weeks until late October each year.

Once bear locations were determined, field crews took hair and other samples at many of these locations to obtain further data. If bear use was verified at a GPS location, sampling followed a standard protocol to collect site, vegetation and bear behavioural information. Variables recorded included the identification of all plant species, percent cover and plant phenology, site variables include slope, aspect and ecosystem classification, and bear descriptions and measurements of feeding, bedding, digging, caching and other bear activities. Analysis of the field data included the determination of bear seasons for each individual based on the bear’s movement to certain habitat types and particular food sources. Seasons identified include Herb/Bulb, Early Fruit, Berry, and Post-Berry seasons.

The relationship between forest practices, site characteristics and bear forage production was also studied. Openings were chosen to provide a range of ages, forest harvest methods, and silvicultural treatments. Stocking levels, canopy closure and bear forage response was recorded and photographs taken of each site. Notes and photographs were also taken when either the block layout or road design reduced habitat effectiveness for grizzly bears.

Historical information on human settlement and development from 1858 to 1962 was collected and compiled, and then linked to an updated grizzly bear habitat suitability and capability map. The 2007 report includes an appendix that assesses historic human impacts on grizzly bear habitat in the Bridge River Valley.

The study area lies near the southwestern edge of the grizzly bear population distribution in British Columbia and includes the Stein-Nahatlatch and South Chilcotin Grizzly Bear Population Units. This area is most easily described as corresponding to the Lillooet Timber Supply Area (TSA). The project focused on movements, habitat use and demographics of grizzly bears in the Cayoosh and Whitecap study areas.

Results of the Study

In 2005, five GPS collars were used to track bears in the Cayoosh study area. This satellite-linked collar technology was unstable and about 1,000 locations were recorded, with field investigations completed on about 10 per cent of the bear points. The 2006 season was more successful, with 10 GPS collars used and more than 13,600 bear locations for the season. Twelve GPS collars were operational in June, 2007 and more than 13,530 locations were obtained for these bears. Further analysis on the full 3-year dataset is required to complete the project objectives. A three-year summary (2005 – 2007) summary of locations by bear by study area is provided in the 2007 report.

In 2007, 184 grizzly bear use locations and 179 random-paired locations were investigated.

Also in 2007, 27 forestry resource management openings were visited, for a total of nearly 70 openings for two years. In general, harvested stands in the wetter ecosystems of the Cayoosh study area retain bear forage production for up to 25 years or more, when canopy gaps are sufficiently large within the block to enable berry shrubs to grow and fruit.  In several cases it would have been possible to maintain the habitat effectiveness of the forage area if a wider old growth buffer had been left between the opening and the feeding unit.

Over 600 historic impact assessment records were used to build an understanding of the human settlement and development impacts in the Bridge River Valley from 1858 to 1962. These records indicate the 1960 flooding of the valley permanently removed highly capable grizzly bear habitat, and that the bear population was already in decline as a result of human settlement and mining in the valley.

Discussion / Implications of the study

The 2007 study was very successful, nearly doubling the point data location available on grizzly bears in the Lillooet area. Concerns remain over data gaps despite the volume of data collected in 2006 and 2007. These gaps were caused by malfunctioning collars providing partial data only, and affecting the overall small sample of bears used to generate results. More time is required to properly assess the composition of the three-year dataset and perform other analysis.

A draft best management practices document has yet to be released for general comment because details of the map and these best management practices are still being crafted.

The historic impact review for the area has been completed, and a report will be provided to BCRP. Work on these issues will continue to improve our understanding of the impacts of development and human activities. As our understanding of historic impacts improves, changes to recommended mitigation and restoration activities will be clarified.

This project has greatly improved our understanding of grizzly bears in the study area, although technical problems with collar operation have slowed down original delivery timeline for resource selection functions. This has affected the timelines for the revision of best management practices for forestry activities.

The bear locations have been assembled into a movement path dataset for each bear which will become part of the home range analysis yet to be completed.

Work on these final products will continue with the expected goal of publishing the results in peer-reviewed journals.

Suggested action/ Future direction

Applications to continue this work and to develop a burning plan to mitigate bear habitat impacts from the hydro reservoirs were rejected at the technical review stage by BCRP. Renewed support from this agency with respect to grizzly bear population recovery is recommended.

It is important to implement the recommended strategies from the reservoir footprint impact analysis and to continue GPS monitoring of grizzly bears to improve the age class, sex and spatial distribution of the dataset, and the development of objectives to address climate change, Mountain Pine beetle, and other habitat impacts.

Conclusion of the Research

Completion of the original project objectives is required to provide a comprehensive understanding of bear habitat use in relation to forest management practices.

Much work remains to be done to recover the Stein-Nahatlatch and South Chilcotin Grizzly Bear Population Units.

  • Source 1 Sue Senger, Tony Hamilton, Michelle McLean. 2007. Ecological relationships between Grizzly bears and forest management in the coastal-interior transition of British Columbia. 2006 Year End Report prepared by Landscope Consulting Services and the Ministry of Environment, for Upper St’at’imc Language, Culture and Education Society and the Lillooet Grizzly Bear Working Group. Available at : [Accessed 03/2021].
  • Source 2 Sue Senger, Tony Hamilton, Michelle McLean. 2008. Ecological relationships between Grizzly bears and forest management in the coastal-interior transition of British Columbia. 2007 Year End Report prepared by Landscope Consulting Services and the Ministry of Environment, for Upper St’at’imc Language, Culture and Education Society. Available at : [Accessed 03/2021].