Just how fat are the fat bears?

Katmai National Park and Preserve’s famous bears from Fat Bear Week are helping provide some answers.

 

Bear 409, “Beadnose,” a sow that won Fat Bear Week in 2018. GIS specialist Joel Cusick is pioneering a new technique for calculating the bears’ weight that doesn’t require pulley systems and tranquilization.

Brown bears are fattening up for winter hibernation in Alaska’s Katmai National Park and Preserve. And starting today, thousands of viewers from around the world will tune in for Fat Bear Week to watch the bears gobble fish from the Brooks River, estimate how well they’re packing on the pounds, and then vote for the portliest in a single elimination bracket. 

But just how fat are those fat bears? A winner will be crowned Oct. 5, but webcam viewers — almost 650,000 cast votes last year — and actual visitors — 15,000 came to Brooks Falls to see the bears in 2019 — are just guesstimating. But there’s hope for achieving greater accuracy: GIS specialist Joel Cusick is pioneering a new technique for calculating the bears’ weight that has broader implications for noninvasive wildlife research. 

The idea came to Cusick, who works for the National Park Service in Alaska, in 2018, while he was working on mapping and surveying at Katmai. A terrestrial lidar scanner, which uses lasers to determine distance and other measurements, was on hand to measure buildings. That’s the device traditional civil engineers use, but when Cusick wandered down to Brooks Falls and stood on a viewing platform 300 feet away from the bears, inspiration hit. He thought: Why not use the scanner to measure a bear’s surface volume instead? 

“I got a laser return from the butt of Otis, one of the more famous brown bears up there,” Cusick said. “I thought, ‘Wow, this just might work.’” 

Lidar, which stands for “light detection and ranging,” emits beams of light to measure three-dimensional objects or areas. When light waves hit an object, they bounce off and return to the sensor. Computers then use the speed of light to calculate the distance between the sensor and all the points. That figure is then processed using software that can model a three-dimensional object. Scanners have become standard technology that is deployed from the ground, the sky and satellites to measure vegetation growth. Now, they’re being used to measure bears’ length, height and girth. 

  • A National Park Service survey team from Anchorage, Alaska, measures the volume of bears bulking up on the salmon buffet of the Brooks River, Katmai National Park, Alaska.

  • A lidar scan of bear 747’s volume next to a photograph of where he was standing near Brooks Falls at the time of the scan.

    Courtesy of Joel Cusick
  • A lidar scan from a different perspective of bear 747's volume. The lidar can't scan through water, so researchers must wait for an opportune viewpoint.

    Courtesy of Joel Cusick
  • Bear 435, pictured in 2019. Fat Bear Week began in 2015 as a National Park Service effort to educate the public about the bears.

  • Bear 151, pictured in 2019. A lidar scanning device only needs from 3 to 11 seconds to pass over the bears. Often, researchers measure them as they’re standing relatively still while waiting for salmon to swim upstream.

  • Bear 775, “Lefty,” photographed in September 2019.

And bears like Otis, a legendary past champion of Fat Bear Week, are actually a pretty good fit for lidar scanning. Bears in Katmai are generally weighed in the spring, when they’re lighter, using a pulley system. The process is resource-intensive, however; it usually involves a helicopter and requires tranquilizing the bear. The 4.1 million acre park in southwestern Alaska (home to more than 2,000 bears) is already remote and mostly accessible only by plane. “In the fall, it’s always been a great mystery how heavy these bears get, because they just can’t weigh them,” Cusick said. 

The devices only need from 3 to 11 seconds to pass over the animal; since the bears are currently preoccupied — fishing for salmon swimming upstream to return to spawning grounds — they stay relatively still as they wait. “I didn’t expect them to be as still as they were,” Cusick said, who described them as “standing like statues.” It initially seemed like their thick fur might prevent the laser from penetrating enough to be accurate, but the wet environment and mist mats it down enough to get a good reading. If they’re partially submerged, however, it becomes a challenge; the laser cannot scan through water. Besides, Cusick needs to get a good recording of the bears’ bellies, which are plump with fish, berries and other foods. “If we can get their belly just swinging right above the water, that’s the largest percentage of their volume and that’s what we hope for,” he said. “It’s a lot of patience, standing there like a photographer, waiting for a perfect shot. We’re doing the same with lasers.”    

“In the fall, it’s always been a great mystery how heavy these bears get, because they just can’t weigh them.”

Inspired by his success, Cusick returned in 2019 and 2020 with a more precise and faster scanner. His work confirmed that people did indeed vote for the fattest bear last year: Bear 747. (The bears are numbered by the park for research purposes.) The winner’s volume was 22.6 cubic feet or 1,416 pounds, compared to the runners-up, who trailed the aptly named 747 at 1,250 pounds — Bear 32, or “Chunk” — and 1,212-pound Bear 151, or “Walker.” The internet sensation began humbly in 2015 as a National Park Service effort to educate the public about the bears, who can gain up to four pounds of weight a day preparing for winter, and their surrounding ecosystem. 

There’s still work to be done regarding the accurate conversion of volume to mass. “The trick to getting the mass of the bear is knowing the density in pounds per square inch,” Cusick said. “That is the part of the equation that is still not determined.” He used a rough estimate to calculate weight, figuring that bears are 60% water and 40% fat.  

The fat bears aren’t being scanned this year due to COVID-19 and staffing constraints; Cusick is always accompanied by a “bear monitor” who knows the bears. (The voting process remains the same this year, however.) But other researchers are eager to continue the work in their own areas of expertise. “I’m trying to get all the ‘ologists’ I work with to step into the 3D world that is possible with this sort of on-the-ground terrestrial laser scanning,” Cusick said. “It’s a fast-growing technology.” 

And the “ologists,” as he calls them — mostly bear biologists so far — are interested. “I’m really excited about his work,” said Lindsey Mangipane, a polar bear biologist with the U.S. Fish and Wildlife Service. “It shows a lot of promise.” 

A recent study shows that polar bear mass is an accurate metric for evaluating the links between what the bears eat and how the population is doing. As sea ice melts, bears are spending more time on land, where they lack access to their traditional prey, such as ringed and bearded seals.

Mangipane and others are working on a study using captive polar bears in zoos, which are trained to step on scales and already have a known weight, to gauge the scanning method’s accuracy. Scanning would be done throughout the year to make sure that the bears’ shape — how fat or skinny they are — isn’t throwing off the results. Tests could start within the year. 

If the lidar scanning proves accurate for captive polar bears, scientists hope to use it as a non-invasive tool in the wild. Less-reliable sea ice means that the biologists’ job has become more dangerous than it used to be. “We used to go out and catch polar bears on the ice,” Mangipane said. “The last few years, the ice wasn’t good enough for us to go out. It’s important, moving forward, that we have new methods to get the data we need to make more informed management decisions.” 

Kylie Mohr is an editorial intern for High Country News writing from Montana. We welcome reader letters. Email her at [email protected] or submit a letter to the editorSee our letters to the editor policy.

 

High Country News Classifieds
  • EXECUTIVE DIRECTOR
    Executive Director Position Announcement POSITION TITLE: Executive Director ORGANIZATION: Friends of Cascade-Siskiyou National Monument REPORTING TO: Board of Directors EMPLOYMENT TYPE: Part-time - Full-time, based...
  • HEALTHY CITIES PROGRAM DIRECTOR
    The Healthy Cities Program Director leads and manages the Healthy Cities Program for the Arizona Chapter and is responsible for developing and implementing innovative, high...
  • CONSERVATION PROGRAM MANAGER
    Grand Staircase Escalante Partners (GSEP) Conservation Programs Manager Job Opening Our Mission: Honoring the past and safeguarding the future of Grand Staircase-Escalante National Monument through...
  • ASSOCIATE DIRECTOR
    Grand Staircase Escalante Partners (GSEP) Associate Director Job Posting Our Mission: Honoring the past and safeguarding the future of Grand Staircase-Escalante National Monument through science,...
  • UNIQUE, ENERGY-EFFICIENT HOME ON ACREAGE NEAR MOSCOW, IDAHO
    Custom-built energy-efficient 3000 sqft two-story 3BR home, 900 sqft 1 BR accessory cottage above 2-car garage and large shop. Large horse barn. $1,200,000. See online...
  • OUTDOOR ADVENTURE BUSINESS FOR SALE
    Missoula Outdoor Learning Adventures (MOLA) - established and profitable outdoor adventure & education business in Missoula, Montana. Summer camp, raft & climb guide, teen travel,...
  • OJO SARCO FARM/HOME
    A wonderful country setting for a farm/work 1350s.f. frame home plus 1000 studio/workshop. 5 acres w fruit trees, an irrigation well, pasture and a small...
  • STEWARDSHIP COORDINATOR
    Join Skagit Land Trust (the Trust), a not-for-profit conservation organization based in Mount Vernon, Washington, and help protect land for people and wildlife. Skagit Land...
  • 2022 SEASONAL SCIENCE EDUCATOR
    The Mount St. Helens Institute Science Educator supports our science education and rental programs including day and overnight programs for youth ages 6-18, their families...
  • POLICY DIRECTOR
    Heart of the Rockies Initiative is seeking a Policy Director to lead and define policy efforts to advance our mission to keep working lands and...
  • CHIEF FINANCIAL OFFICER
    Self-Help Enterprises seeks an experienced and strategic CFO
  • CONSERVATION SPECIALIST - LAND PROTECTION FOCUS
    View full job description and how to apply at
  • RIVER EDUCATOR & GUIDE
    River Educator & Guide River Educator & Guide (Trip Leader) Non-exempt, Seasonal Position: Full-time OR part-time (early April through October; may be flexible with start/end...
  • LAND AND WATER CONSERVATION DIRECTOR
    The Land and Water Conservation Director is a full-time salaried position with the Mountain Area Land Trust in Evergreen, CO. The successful candidate will have...
  • FOOD SYSTEMS ENVIRONMENTAL FELLOWSHIP
    If you were to design a sustainable society from the ground up, it would look nothing like the contemporary United States. But what would it...
  • EXECUTIVE DIRECTOR
    The Rio Grande Headwaters Land Trust (RiGHT) is seeking an Executive Director who will lead RiGHT toward a future of continued high conservation impact, organizational...
  • COMMUNITY ORGANIZER
    Help protect Montana's water quality, family farms and ranches, & unique quality of life. Work hard, meet good people, make the world a better place!...
  • NEW BOOK:
    True Wildlife Tales From Boy to Man. Finding my voice to save wildlife in the Apache spirit. 365+ vivid colorful pictures. Buy on Amazon/John Wachholz
  • CHIEF OPERATIONS OFFICER
    with Rural Community Assistance Corporation. Apply here: https://www.marcumllp.com/executive-search/chief-operations-officer-rcac
  • CARPENTER WANTED
    CARPENTER WANTED. Come to Ketchikan and check out the Rainforest on the coast, Hike the shorelines, hug the big trees, watch deer in the muskeg...