KALISPELL - Grizzly bears are slowly gaining ground in Montana's northern Rocky Mountains - where populations are growing at about 3 percent per year - but researchers warn the scales could tip if long-term protection efforts are relaxed.
"The trend is up," said research biologist Rick Mace, "the trend is good. But I think it's going to take continued vigilance" before the bears can be removed from the endangered species list.
On Wednesday, Mace offered the first glimpse at data he's been collecting since 2004. At that time, he said, scientists using DNA analysis had pegged the number of grizzlies in the region at about 700. He presented the information at an annual interagency meeting of bear managers in Kalispell.
But they didn't know if that number was going up or down, didn't know how fast the bears were reproducing or dying off.
And so Mace kicked off his own study, trapping and tracking individual bears in an effort to better understand population trends. His goal, he said, was to establish an estimate of population change over time.
To do that, he needed some basic data, primarily reproductive rates and survival rates - who was born and who had died.
Coupled with the DNA population estimate, he said, the trend study will provide a powerful tool for understanding the state of the grizzly.
Mace and his crews worked on foot and from boats, on horseback and in helicopters, trapping and snaring and collaring grizzly bears up and down the northern Rockies, extending well into Canada at times.
He monitored between 25 and 45 female grizzlies each year, using GPS collars to pinpoint bears in real time across the landscape. He knew when they went into dens, and when they came out, when they crossed roads, and when they died.
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The earlier DNA work had provided a map of grizzly density - way more up around Glacier National Park, and far fewer down in the Scapegoat Wilderness, for instance - and Mace echoed that spread with his research bears. If he had 25 bears collared, he made sure 10 of those were in Glacier, and three were on the Rocky Mountain Front, and one was in the Scapegoat.
In addition, he parsed bears by type - because bears caught raiding orchards had a different probability of survival than bears caught foraging in the wild.
For the youngest bears, he broke the year into cycles - the 190 or so days they spent as cubs, the 160 days they spent denned up, the 215 days they spent out and about as yearlings - and he worked up survival rates for each cycle.
For the adults, he gathered a monthly survival probability, and an annual survival probability, tracking them for years to establish their reproductive rates. Mace figured out the probability that a bear would have cubs, or lose cubs, or raise yearlings.
Turns out, about a third of adult female grizzlies would travel with cubs in a given year. And those cubs, he learned, had a 61 percent chance of survival. Among yearlings, the chance of survival was 68 percent.
The annual chance of survival jumped to 88 percent for subadult grizzlies, and 96 percent for adult bears.
Of the 83 adult bears tracked for the research, eight died. But of the 36 "problem bears" tracked during that same time, eight more died, showing that survival rates were far lower for troublesome bruins.
The average research bear lived to age 28.
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Overall, Mace said, grizzly bear populations in the Northern Continental Divide Ecosystem are increasing, on average, at about 3 percent per year, although that fluctuates from year to year. It is a slim margin of success, he said, but perhaps not surprising given the bears' long life and relatively slow reproductive rate.
The species' recovery, since gaining federal protections some 30 years ago, "has kind of been a slow and quiet thing," he said. "It's been a very slow growth rate."
He credits the gains on more bear specialists on the ground, more successful relocations of grizzlies, habitat protections and improvements, the end of Montana's grizzly hunt, better road management, public education, improved public sentiment, bear spray and the overall impact of the Endangered Species Act.
In addition, he said, the "sanctuary status of Glacier National Park has been of paramount importance."
Concerns, however, linger, not least of which is the question of whether Glacier Park has reached its carrying capacity in terms of bears. In addition, global warming is causing bears to den later and emerge sooner, resulting in a longer "season of danger" outside the den.
"There are so many variables," Mace said. "This population is growing, but there's still work to do."
Reporter Michael Jamison can be reached at 1-800-366-7186 or at mjamison@missoulian.com.
