Grizzly population growing steadily

Bear managers suspected the Northern Continental Divide grizzly population has been increasing, and now a six-year trend study has confirmed an annual average growth rate of 3 percent.

The findings were presented at a meeting Wednesday in Kalispell by Rick Mace, a research biologist with Montana Fish, Wildlife and Parks who led the population trend study.

“The trend is up, the trend is good,” Mace told a panel of wildlife and land managers at Fish, Wildlife and Parks headquarters.

He added that there needs to be continued vigilance in monitoring a relatively small population that can be vulnerable to a variety of circumstances from year to year.

A 2004 genetic population study led by the U.S. Geological Survey produced a “snapshot” population estimate of 752 bears that year.

The trend study was designed as companion research to determine whether the population was increasing or declining.

It involved monitoring with GPS collars between 25 and 45 female grizzly bears each year, with a focus on birth rates and survival rates for adults and their offspring. That proved to be a daunting task over an 8-million-acre study area, most of it rugged and remote.

A team of about a dozen people used hiking, horses, helicopters, boats and vehicles to capture, collar and then follow the research bears. And the work had to be properly distributed, with a higher number of collars in the more densely populated Glacier National Park area, and fewer in the less populated southern portion of the Bob Marshall Wilderness Complex.

Then the study involved rigorous statistical modeling to produce probabilities, birth rates and survival rates.

The study found that annual survival rates increase as bears grow older: cubs of the

year at 61 percent, yearlings at 68 percent, subadults at 88 percent and adults at 95 percent. It found that management bears that have had conflicts with people have an 80 percent annual survival rate.

It found that there is a 32 percent probability for females to have cubs each year.

Those and other factors were boiled down into the all-important statistic known as “lambda,” the population trend.

“The basic trend of this population is that it has been growing at about 3 percent a year” during the study period, Mace said.

However, he stressed that is an average rate for the entire population. Reproductive growth actually “wobbles” from year to year, and some parts of the ecosystem have higher rates than other parts.

“But 3 percent as a mean is a very good growth rate for grizzly bears,” he said.

Mace attributes the growing population to a variety of changes that have occurred, starting with the listing of grizzly bears as a threatened species in 1975. A grizzly bear hunt was phased out entirely by 1990, and forest road densities have been decreasing since 1995.

Montana’s grizzly bear management specialists deserve considerable kudos, Mace said, for reducing bear-human conflicts. They have educated the public, introduced bear-proof food and garbage containers, and made considerable efforts in working with management bears.

The now-widespread practice of carrying bear spray as a deterrent rather than firearms has made a big difference.

“I do believe there been a public attitude change” that has increasingly favored bear conservation over the years, Mace said.

The study’s findings were not surprising to Jim Williams, the state’s regional wildlife manager.

“We knew it had to be happening,” Williams said, because grizzly bears appeared to be expanding their range beyond the Northern Continental Divide recovery area that was defined years ago.

“Now we’re seeing the grizzly bear population expanding into areas where we haven’t seen them for years,” said Mike Madel, the grizzly bear management specialist on the Rocky Mountain Front.

Madel gave a presentation at the meeting showing how grizzly bears have been using the Marias, Teton and Sun River drainages to move more than 60 miles from the front in recent years.

Madel said he has long worked with about 150 ranchers on the front, but lately he has been holding meetings with people in the Shelby, Simms and Fairfield communities who are not familiar with the possibility of grizzly bears roaming nearby.

Telemetry monitoring of one female bear showed that it was using the cover of river corridors by day and then moving into open crop lands at night.

Madel said population growth may not be the prime driver behind the eastward expansion of grizzly bears. There are other factors, such as learned behaviors in discovering new food sources on the plains that are passed onto their offspring.

And Mace cautioned that the growing population trend of recent years may not be permanent. Functioning as sort of a sanctuary that has produced its relatively high population density, Glacier Park may reach a carrying capacity for grizzly bears.

“Funny things start happening” when wildlife populations reach their limits, he said, such as lower birth rates and lower survival rates.

Reporter Jim Mann may be reached at 758-4407 or by e-mail at jmann@dailyinterlake.com