At the Northern Continental Divide Ecosystem meeting last week, agencies gathered to provide updates on their fall projects of the predominantly bear-ish kind.
The NCDE is a subcommittee of the Interagency Grizzly Bear Committee, which promotes grizzly bear population recovery across habitats and national borders.
U.S. Geological Survey scientist Tabitha Graves from the Northern Rocky Mountain Science Center talked about the bear population trend project she’s been working on.
The project uses rub tree data to estimate grizzly bear population numbers, and Graves summarized that at the Continental Divide ecosystem level, the population is increasing. But density — the number of bears in an area — varies by location.
Graves said that the science center team is also working on developing a family tree for the ecosystem’s grizzlies, which will incorporate data from both the United States and Canada.
The dataset is large, with over 2,000 bears, so it could take months to complete the family tree.
They also continue to study one of the bears’ main foods — huckleberries.
In addition to identifying huckleberry consumers and measuring the effects of drought and pollination on the plants, the USGS team will use ScienceCache in citizen science programs to monitor huckleberry phenology. The ScienceCache app has citizen science hikers download a route, and then directs them with clues to tagged huckleberries. Hikers answer a series of questions to provide scientists with information about the health and condition of each plant, and then they upload pictures of the plants. The data is sent to a USGS database. Scientists can then evaluate the effects of weather and climate on huckleberries, which are an important food source for grizzlies.
This year, the USGS has four test trails in Glacier National Park and may also include a couple on Forest Service trails.
In response to Graves’ presentation, the public expressed concern about hikers possibly going off trails to find huckleberries. Graves said that the ScienceCache app, which is still in the test phase, will include warnings about staying on marked trails and information about bear safety. She also noted that the test trails are all on marked routes.
Cecily Costello, a biologist for Montana Fish, Wildlife and Parks, provided results from a continuing study on radio-marked grizzlies. The program involves capture and monitoring of mostly female bears, with a few males. The program looks at bear reproductive success and mortality in a Demographic Monitoring Area.
Of 73 bears monitored for survival and reproduction, there were seven adult bear mortalities in 2016, Costello reported. These numbers are normal, she confirmed. Rates were about 95 percent survival of females and 90 percent survival of males from 2004 to 2014.
In 2016, 43 females were observed for reproductive success. Half did not have cubs, but some had yearlings or even 2-year-olds. Last year had a high number of cubs, so Costello wasn’t concerned about low numbers. The mean litter size, for six litters in 2016, was 2.2 cubs.
There were no cub mortalities in 2016, but there were eight yearling mortalities. Two yearlings separated from their mothers early, before age two, and were counted as mortalities.
“We do assume that if they’re not with their mother they’re dead, but we know that’s not always the case,” Costello said.
Based on the number of mortalities among marked bears, FWP calculated that the total mortality of all bears in the study area in 2016 was around 22 deaths, which is consistent with the patterns documented in 2004-2014.
“The last couple years have been relatively low,” Costello remarked.
Scientists have a threshold for maximum mortality rates, and the numbers fall well below the level for population sustainability. All the population data parallels the estimated population growth rate of 2.3 percent per year. It’s difficult to be sure about the actual number of bears and deaths, though.
“That’s really a limitation that we have in this ecosystem. If we have a population estimate, it’s something we can only get on a periodic basis, not a yearly basis,” Costello said.
Other current FWP projects include tracking potential paths of male gene flow; and comparing morphometrics — body fat and health condition — of bears on the eastern and western sides of the divide, and evaluating changes in bear body composition over the years.
FWP is also interested in evaluating how roads, fires, and forest management affect habitat selection. Additionally, they’d like to analyze the geography of bear/human conflicts to determine why confrontations happen more in certain places.
Finally, they’re looking to conduct a statewide survey to assess how human attitudes toward grizzlies have changed, and how they differ by region, with the expansion of the bear population.