Mounting evidence shows nutrient-rich seeds from endangered whitebark pine trees are an important food source for grizzly bears in Banff National Park.
While this has been well documented in other areas, including Montana and Wyoming in the U.S. and Alberta’s Willmore Wilderness area, ongoing research shows it’s the same in Banff.
Canmore researcher David Hamer, who has a doctoral degree in wildlife ecology, first found grizzly bears had been raiding squirrel middens (piles of discarded cone debris) to get to whitebark pine seeds at several Banff locations a few years back.
But he continued to do more field work last year, noting he used GPS data from 16 collared grizzlies to see where they had spent time; then searched those areas for squirrel middens and whitebark pine.
Bears either raid middens or climb trees to get to the nutritious seeds, and Hamer found most bears were digging and devouring whitebark pine seeds where they’d been stashed in squirrel middens.
“Thirteen of 16 bears had eaten whitebark pine seeds – that’s 81 per cent,” he said, noting this year he will study GPS data from the remaining bears collared as part of a Parks Canada-Canadian Pacific Railway study on railway bear mortality.
“Some of these squirrel middens were heavily excavated and there were inconspicuous bear trails leading into them. There was lots of use. It was very impressive.”
Whitebark pine is endangered under Alberta’s Wildlife Act and under the federal Species at Rick Act. It’s found at high elevations from treeline to sub alpine forests, and can live up to 1,100 years.
The species has been in decline over much of its range in Alberta and B.C., as well as the northern United States, due to invasive white pine blister rust, mountain pine beetle, wildfire suppression and climate change.
Hamer’s research builds on an earlier study he did with retired Parks Canada fire and vegetation expert Ian Pengelly, which was published in 2015 in the scientific journal, The Canadian Field-Naturalist.
In that study, bears had dug up 24 of 36 middens. Bear scat containing whitebark pine seeds was also found at several sites.
“Those observations were, to our knowledge, the first conclusive evidence that grizzly bears in Banff National Park eat whitebark pine seeds,” Hamer said.
In the Greater Yellowstone ecosystem, extensive research determined whitebark pine seeds are a major source of energy for bears there, and when whitebark pine seeds were abundant, “grizzly bears eat virtually nothing else.”
That study found years with high cone crops had fewer bear-human conflicts because high elevation whitebark pine stands are typically remote from human development. Also in those years, a higher number of cubs per female were born the following spring.
In contrast, for years of small pine seed crops, mortality of adult female grizzly bears averaged 2.3 times higher, and mortality of sub-adult males was on average 3.3 times higher than in years of large seed crops, which the authors attributed to the tendency of bears to range closer to human facilities in years of pine seed scarcity.
Hamer said the same could be true for Banff, noting he hopes findings in Banff are helpful to managers in Banff National Park, where black and grizzly bears have high mortality levels.
“Because whitebark pine occurs at high elevations on steep slopes where human use is low, whitebark pine may be important in keeping bears in habitat where risk of human-caused mortality is lower,” he said
Meanwhile, Hamer has also been studying if limber pine seeds form a significant part of bear diets. Limber pine was assessed as endangered by COSEWIC in 2014, but not yet listed under the Species At Risk Act.
While previous research elsewhere shows bears don’t typically eat limber pine seeds, a recent paper by Hamer shows there’s three locations in Banff that are used, including one heavily used by bears.
Hamer looked at several study sites. Four were in Banff National Park, including three in the Bow Valley between the east park gate and Bow Valley Parkway.
Only one site along the Bow River escarpment, which has frequent small gullies, provides red squirrel habitat relatively close to limber pine stands.
“It appears that limber pine stands, typically, are not red squirrel habitat and, hence, are less likely to be sites where bears obtain pine seeds,” he said.
“But there has been substantial use of bears eating limber pine seeds from squirrel middens at this site.”