Study gives griz mortality a mixed review
A new report by the U.S. Fish and Wildlife Service gives the human-caused grizzly bear mortality rate in the Northern Continental a mixed review.
On one hand, the study shows that overall, grizzly bear deaths fall in the acceptable range. But the female mortality rate doesn’t. It’s slightly higher than it should be.
Why does this matter?
Because in order for grizzly bears to be delisted from the Endangered Species List human-caused mortality rates need to fall under acceptable limits.
The new mortality rates are based on a recent DNA population estimate for the Northern Continental Divide Ecosystem that concluded there are about 765 grizzlies roaming the 8 million acres of mountains and valleys from Glacier Park south to roughly Ovando.
The report, written by U.S. Fish and Wildlife Service grizzly bear recovery coordinator Chris Servheen, looked at the current population size and the average mortality rate over the past six years.
From 2003 to 2008, on average humans killed 21 grizzly bears a year and 9.5 of them were females.
According to Servheen’s report, biologist Rich Harris in 1984 calculated that a sustainable level of human-caused mortality is no more than 6 percent of the population if no more than 30 percent of this known human-caused mortality is females.
The recovery plan for bears in this area actually sets the standard even lower, with a total mortality rate of 4 percent — of which no more than 30 percent can be females.
As such, the current average of 21 deaths a year is below 4 percent, which comes out to 30.6 deaths on average. But the number of female deaths, which amount to an average of 9.5 per year, is over the acceptable limit of 9.18 deaths per year.
In other words, the area needs less female bear mortality.
The study also assumes that the bear population has stayed relatively stable since 2004 when the DNA study was completed.
Servheen writes, “The primary assumption that must be accepted if this number is to be applied post-2004 is that grizzly populations do not increase or decrease rapidly. Since we have no information that there has been a major change in the number of grizzly bears in the NCDE since 2004, and if we assume that grizzly populations increase or decrease slowly under most conditions, it seems logical to continue to apply the 2004 population number post-2004.
“Available information indicates that grizzly bears are increasingly showing up in places outside the NCDE recovery zone boundaries with bears in 2008 southeast of Shelby, in Simms 26 miles west of Great Falls, at Wolf Creek, and at Drummond. This anecdotal distribution information indicates the NCDE grizzly population is expanding in range which would be consistent with an increasing population,” Servheen writes.
But at least one environmental group is taking issue with the assumption that the grizzly bear population is stable.
“While we appreciate that the memorandum acknowledges the long-standing problem with excessive female mortality,” said Swan View Coalition Chair Keith Hammer. “We don’t appreciate the risks taken to make those excesses appear marginal.”
Hammer claims the Service should have used more conservative numbers that came out of the DNA study. He noted the study also showed there could be as few as 715 bears in the NCDE. He also claimed the study should have looked at the actual number of bears that were positively identified in the study — 563 individual bears.
But U.S. Geological Scientist Kate Kendall said Servheen’s work was “a reasonable argument.”
Kendall headed up the DNA study. She notes that bears are doing fairly well and they are expanding their range.
Still, there aren’t very many of them spread out over the landscape and grizzly bears face many challenges, from poaching to subdivisions to other human threats to their habitat, she noted.
“This doesn’t mean our (conservation) work is done,” she said.
Kendall has been a longtime proponent of conservation easements on private land and other safeguards for bear habitat. Grizzly bears need a lot of space to roam.