Take action on behalf of grizzly bears and their habitat
Image © Roger Hayden - all rights reserved
Population Trend
A Reflection of Mounting Mortalities
Grizzly bear mortalities have increased dramatically since roughly 2000, far in excess of anything that can be explained by changes in population size. The most important trend is the substantial increase in mortality that followed hard on the heels of when we lost most whitebark pine in the ecosystem. Grizzly bear conflicts with livestock producers and hunters have surged dramatically since the loss of whitebark pine and cutthroat trout, which is consistent with a turn by many bears to eating more meat in compensation for loss of pine seeds and trout. The increase in hunter-related mortalities has occurred despite a substantial decline in hunters afield (see Trends). This belies claims on the part of agency personnel that hunters are “behaving better” than in the past.
Trends in Total Mortality
The graph at left shows a 3-year running average of total known and probable bear deaths in the Yellowstone ecosystem. The dominate trend since roughly 2000 has been two periods of dramatic increases, at the same time that population growth stalled and then turned negative (see below). The most important trend is the substantial increase beginning around 2007, hard on the heals of when we lost most whitebark pine in the ecosystem. 2014 wasn't bad insofar as mortality was concerned, at least compared to the years before. But 2015 and 2016 were record-breakers, with 2017 shaping up to be bad as well.
Population Trends
2004-2016
Agency spokespeople love to claim that the Yellowstone grizzly bear population has increased without pause up until the present, including rather astounding claims that the population went from around 500 bears in the recent past to over 1000 now. These claims are nothing more than fabrications born of comparing apples with oranges--the results of one incommensurate method with another. The figure above shows three trend lines (the solid darker lines) produced by three different methods (the colored bands around each line are bounds of uncertainty). All three methods show a population exhibiting little or no growth since 2004, with evidence of decline during recent years.
2014-2016
This graph focuses on the period 2014-2016, which encompasses two years of record breaking mortality (2015 and 2016). The decline in population size is exactly what we would expect given unsustainable numbers of grizzly bear deaths. Interestingly, government spokespeople claim "we cannot conclude the population has declined" simply because the confidence intervals for 2014 and 2016 estimates overlap. In fact, the preponderance of evidence overwhelming supports concluding there was, in fact, a decline--another instance of government disingenuity if not dishonesty.