Populations are limited by both food production that affects reproduction and death rates. The southern portion of the study area was heavily logged and had a large gas exploration program in the late 1970s and 1980s. The grizzly bear population rapidly increased during this time period. This southern area, and likely the northern portion of the study area, the populations appear to have reached carrying capacity and are now regulated primarily by changes in food production. Monitoring of huckleberry production since 1979 in the southern area found a decline between 1997 and 2010 and a resultant drop in reproductive rates of bears and population decline. This decline appears to have abated and the population is now increasing again.
The latest report from SRGBP in 2014 produced the following findings.
Highway 3, the railway and associated human settlements have been shown to be the source of disproportionately high mortality along the Highway corridor in our study area. This has led to an interesting scenario involving source and sink dynamics. Whilst hunting mortality is more dispersed, mortality along the highway corridor is concentrated. Many collisions with bears that occur on railways are family groups; therefore, females of reproductive age may be at greater risk of mortality. All cubs and the majority of yearlings are known to also perish if their mother is killed (McLellan, 2015). It was shown by Lamb et al (2016) that there was much greater movement into the corridor area than out. This increases the impact of mortality beyond the source area, affecting populations well outside of the study area. It is important to separate the causes of mortality to determine which we are able to mitigate. As the project has found, the increase in mortality from highways and railroads coupled with the consistent levels of mortality from other sources are leading to population decline. Whilst it is difficult to mitigate mortality from sources such as road and rail, it may be necessary to reduce mortality from other sources until the decline can be alleviated and the population can become stable again. In light of this, the project has resulted in some recommendations for management policy which are:
For our 2011 report and other papers published by our scientists and collaborators please visit the additional resources page