By Joseph Robertia
For Kenai Peninsula brown bears — deemed by the state as a species of special concern in 1998 — there are many factors that affect their population, and since the overall number of brown bears is not known, it’s difficult to say if these mortalities are insignificant or severely threatening the population.
“We only know how many die, not how many are living,” said John Morton, a supervisory biologist with the Kenai National Wildlife Refuge. “We have no empirically based population estimate.”
The Kenai is one of Alaska’s fastest-growing regions, and with human population expansion comes development of homes and roads that fragment bear habitat. These activities also increase bear-human encounters, from the handful of bruins taken each year as part of established hunting quotas, to the scores of brownies killed annually in defense-of-life-and-property shootings.
Adding to this, Kenai brown bears are geographically isolated. The peninsula is connected to the Alaska mainland by a narrow, nine-mile wide isthmus between Cook Inlet and Prince William Sound, and human activity in this narrow corridor is believed to restrict movement of bears on and off the Kenai.
The population number typically thrown about is 250 to 300 brown bears on the Kenai, but this number is just a best guess. That’s about to change, according to Morton, who is point man for an ongoing project that aims to estimate the brown bear population in the Kenai National Wildlife Refuge and Chugach National Forest — a project area 2.73 million acres in size, after subtracting acreage associated with Tustumena Lake, Skilak Lake, and the Harding Icefield.
“It’s been kicked around for years under the auspices of the Interagency Brown Bear Team,” Morton said, referring to the Alaska Department of Fish and Game, U.S. Fish and Wildlife Service, U.S. Forest Service and National Park Service, which all convened in the mid-1980s to monitor and research brown bears on the Kenai Peninsula.
The challenges to counting peninsula bears — frequently referred to as coastal brown bears, rather than grizzlies, due to ecological differences — are more difficult than in many other areas of the state, and this has repeatedly been a hurdle to conducting a census.
“The problem is coastal brown bears are usually in more open habitats, so they can be aerial surveyed,” Morton said. “Here on the peninsula, with the densely wooded lowland forests, that’s just not an option.”
Instead, researchers have opted to use a DNA mark-recapture approach to come up with a brown bear estimate. This is done by dividing bear habitat into cells that form a grid. Each cell has a lure station baited with a mixture of fermented fish oil and cow’s blood, surrounded by barbed wire.
“Bears are drawn in by the lure, but they don’t get a food reward,” Morton said. “And as they pass the wire — stepping over or going under it — their hair gets caught in the barbs.”
The monthlong hair-sampling portion of the project began June 1, and Morton said 150 cells have been deployed, with more planned. Later, this hair will be sent to a lab, Wildlife Genetics International in British Columbia, Canada, where it will be analyzed over the next six to eight months to determine the sex of each sampled bear and its individual genotype.
“We expect to sample up to 200 stations, systematically distributed at nine-kilometer intervals,” he said. “We’re using two helicopters with two, four-person crews assigned to each one. These two crews leapfrog each other from one sampling point to another, deploying and retrieving traps and collecting hair samples.”
Morton said that, per helicopter, 16 to 20 hair stations are visited each day, which equates to checking each one about every seven to 10 days. The number of hair samples retrieved has varied depending on location.
“Some stations have had zero and some stations have had up to 721, but 12 samples seems to be about the average,” he said. “We’re hoping for 12,000 samples over the course of the study.
There are some caveats, though. There are many more black bears than brown bears on the peninsula, so their hair samples will undoubtedly be well-represented at the collection stations. This hair will be archived for later use.
Weather, such as the frequent rain near Seward, can degrade the DNA of the hair samples, and this too has been taken into account by biologists.
“Of the 12,000 samples we’re hoping to get, we’re expecting only about 10 percent — 1,200 — to be viable brown bear samples,” Morton said.
Once analysis is complete and a DNA marker is established for each individual bear, Morton said a minimum count for brown bears will be known, but this is not the true population estimate. From there, recapture rates from the bears that revisited the stations must also be reviewed, and a mathematical formula applied to determine an estimate closer to the true number of brownies on the peninsula.
The keyword still is estimate, since the study area is primarily the backcountry, and areas close to houses, cabins, trails and other areas where it is illegal to bait bears have been avoided for public safety reasons.
“We’re doing this in as safe a way as possible,” Morton said. “We’re respecting all the buffers imposed by state regulations.”
Not counting the bears close to town is just one aspect that will affect the overall accuracy of the project. Another drawback of this type of study is it is just a snapshot in time. It doesn’t give any indication of the overall health of the bears studied or predict what the population will be in the future.
Despite these imperfections, Morton said the research is still a step in the right direction, since it will reveal much more information about peninsula brown bears than currently is known.
“Something needed to be done,” he said. “The status quo of ‘very little info known’ wasn’t working.”