Scanning Bears:

Who is the fattest of ’em all?

A unique public outreach campaign involving judging the “Fattest Bear” showcases the natural wonders of Alaska, and terrestrial laser scanning.

By Gavin Schrock
By Gavin Schrock

Consulting Editor | AEC

Every summer Alaskan Brown Bears (Ursus arctos), return to the Brooks River in Katmai National Park and Preserve to gorge on migrating salmon, bulking up in anticipation of a long winter hibernation. “Fat Bear Week”  is an annual event that celebrates the impressive girth of the local bears and the calorie rich southwest Alaska ecosystem that supports them. The capstone event is an online bracket style matchup of bears where the public votes to crown the “fattest bear” among a community of these stately creatures.

This is a unique educational and fun event! As the Katmai National Park Facebook page notes: “The ballooned bears compete belly to belly in a beefy brawl to the final. Which overweight omnivore will pull off a weighty win?” Gentle humor aside, this event has also become a splendid showcase for the capabilities of terrestrial laser scanning (TLS), but also a testbed for using TLS as a non-invasive method for measuring wildlife. “You are not able to step off the viewing platform, walk up to a live bear and pull out a tape measure and weigh it,” says Joel Cusick, National Park Service (NPS) GIS Specialist, “We feel that TLS may be a viable method for gauging size and metrics (length, height, girth) of  bears as well as provide biologists a key component to estimate the mass of bears.”

The contest

Six years ago, Fat Bear Tuesday was started by a ranger at Katmai where they had a bracket style competition between a selected group of the park’s very fat bears to engage the public in this phenomenon of brown bears in hyperphagia to prepare for winter, and it was a success. This morphed into Fat Bear Week.  

Today, participants watch the bears on a live video “bear cam.” They follow their favorite bears and cheer them on as they would in a sporting event. Participants vote for their favorite bear. The bears with the most votes move up in the bracket. Participants support their favorite bears and there is general good will throughout the competition. There are fans who can recite the history of the competition just as there are sports fans who can chronicle championships regardless of where their teams finish. 

The Fat Bear Week competition is done in partnership with Katmai National Park and Preserve, the Katmai Conservancy, and

To be clear, the competition winner is decided by online voting, but the scan results confirm that the winner was indeed, the largest of the group. Overall fatness or largeness is just one thing that people could choose to vote for. They could also vote for bear’s annual overall growth like that experienced by cubs over the season, extenuating circumstances such as a mother’s cost of raising cubs or many other things. Fat Bear Week is a subjective competition and there is no one correct set of criteria votes are based on.

The online voting, hosted by, is a philanthropic media organization and a multi-media division of the Annenberg Foundation. Created by filmmaker and philanthropist Charles Annenberg Weingarten to champion the selfless acts of others, inspire lifelong learning and bring people closer to nature, is home to more than 300 original films and a massive library of world-class photography from all over the globe. In addition, recently launched Pearls of the Planet, a growing collection of live HD cameras that provide people with an unprecedented view into the lives of amazing animals and beautiful places around the world. As an advertising-free philanthropic media organization, regularly provides grants to organizations focused on improving the human condition and the planet”. One of their examples of wildlife webcams is at Brooks Falls in Katmai Park, site of the fat bear event.

“This competition is designed to help people learn and understand the importance of fat bears,” says Amber Kraft, Lead Interpretive Ranger at the park. “Each winter, curled snug in their dens, brown bears endure a months-long amine. During hibernation, bears will not eat, or drink and they will lose one-third of their body weight. Their winter survival depends on accumulating ample fat reserves before entering the den. Katmai’s brown bears are at their fattest in late summer and early fall after a summer spent trying to satisfy their profound hunger. 

“Each bear faces its own challenges in order to gain the body mass necessary to survive. Adult males need to grow large to dominate the best fishing spots and secure mating opportunities. Female bears need to gain weight for their own survival as well as to support the birth and growth of cubs. Bear cubs experience the same hunger as older bears but also undergo tremendous growth spurts. Juvenile bears living on their own for the first time must navigate a gauntlet of hazards to establish a home range and find food without mother’s guidance.  

“Bears gorge on the richest, most easily obtainable foods they can find. In Katmai National Park, that most often means salmon. Dozens of bears gather at Brooks River to feast on salmon from late June until mid-October. Perhaps no other river on Earth offers bears the chance to feed on salmon for so long. Fat bears exemplify the richness of Katmai National Park and Bristol Bay, Alaska, a wild region that is home to more brown bears than people and the largest, healthiest runs of sockeye salmon left on the planet. “

There are dozens of bears that frequent Brooks Falls for their pre-hibernation feeding, and from these, pairs of bears are arranged into voting brackets. Voting extends over the week, narrowing the pack down to two finalists and a grand champion. In 2020, the crown went to bear “747” with over 47,000 votes from all over the globe. Numerous scans of the top bears concurred. There is also a Fat Bear calendar produced each year featuring the star bears.  The calendar is created by the Katmai Conservancy and is sold to raise funds for the park.

Screen shot from the web cam at Brooks Falls, in the Katmai National Park and Reserve

“Katmai National Park, which is near King Salmon Alaska is the park where Brooks Falls is, and where these bears live and eat their copious amounts of salmon,” explains Cusick, “The event is done in concert with the Katmai Conservancy, and to get the word out about these very rich ecosystems. Mike Fitz, a former Ranger with Katmai National Park, is now working for and he came up with this idea of a competition several years ago. It has kind of grown over time, especially with the explosion of wildlife webcams where for instance, anybody in the world can view these bears and watch them grow over a course of a summer and fall.”

“In the world of a bear, to get fat is good − to eat a lot at this time of year before the long winter months.”

“In the world of a bear, to get fat is good — to eat a lot at this time of year before the long winter months is how they are. That is an element of natural selection for them, and there is a huge amount of fish just sitting right there in front of them — it’s kind of like an all-you-can-eat bear buffet,” says Cusick. And they don’t have to expend a lot of energy to do that. Salmon, an anadromous species, migrate from the sea annually and spawn, creating essentially what are “nests” in the river bottoms (known as “redds”).

“Brooks River is short by Alaska standards and between large lake systems at the headwaters of the Bristol Bay watershed.  Combine the geography with a 10 foot falls that isolate the salmon these bears don’t have to wait for the salmon to enter smaller tributaries making this easy pickings both in the early summer and late fall,” he adds. “The fish get crowded in there in the fall spawning season, and we also see bears scooping up paws full of mud to pick out the high protein Salmon eggs (and if you have ever had ‘Ikura’ at a Sushi restaurant, the eggs are probably quite tasty for the bears as well). It is all quite easy pickings for a bear to eat — eating until they almost explode.”

Bear 151 (Walker) at the lip of the falls

Cusick works out of the Alaska regional office of the US National Park Service in Anchorage, Alaska. He emphasizes that he is a “GIS” guy” and not a surveyor, but he sells himself short. I know firsthand from having also surveyed and mapped in Alaska, that there is a lot of overlap. The vast expanses of wilderness provide the same challenges for any geospatial endeavor. Cusick is a noted regional specialist in the use of GPS (now GNSS as the number of satellite constellations has grown). He maintains a pool of GNSS field equipment that “ologists” (as he calls them, like geologists and field biologists) can check out for various field mapping needs. This can include delineating wetlands, mapping of trails and habitats, etc. “My background is more in the mapping grade world. Usually I am happy to get 10 cm out in the open. But lately, I have been trying to push that envelope as high quality, precision and accuracies are much more achievable in recent years,” he adds.

The technologies

Other geospatial field work for the NPS has grown to include some drone (UAS) work, and the use of scanners to support facilities development, upgrades and guiding historical preservation work. Cusick’s team acquired a surveying robotic total station in 2018 to support various NPS needs. Their Trimble SX10 is not only a high precision total station, but it can also do limited laser scanning. While not as high speed as dedicated scanners, this hybrid in addition to being a high precision total station, provides scans, and companion images that are precisely geospatially registered. This gave Cusick the idea of adding some high tech to Fat Bear Week.

Joel Cusick with the Trimble TX8 scanner, and a bear!

In 2018, Cusick decided to do a proof of concept. While doing other work at Katmai with his SX10, he decided to try scanning some of the bears. At over 26,00 points per second, the results proved that a scanner could provide a decent model of a bear, but as the subject tends to move, thoughts turned to a higher speed scanner. In 2019 Cusick brought a Trimble TX8 to the site, with up to million points per second, the scan time per bear could be reduced to a few seconds. And while the processing and registration steps for a dedicated terrestrial scanner might take a bit more work, the brief scan window would be more of a snapshot. “We can window in on a view, picking an area with the bear in it, and little else, and the scan goes quite fast,” Cusick says. Modern scanners use eye-safe lasers, operate almost silently, and do nothing to harm, or disturb the feasting bears.

“Modern scanners use eye-safe lasers, operate almost silently, and do nothing to harm, or disturb the feasting bears.”

One of Bear 747’s 3D mesh models captured by the scanner. 747 was this years’ winner by popular vote and scientific method.

The procedure changed this year. Cusick says in 2019, they used a more traditional surveying style scanning method, setting the instrument up over a survey marker with known coordinates.  They wanted more flexibility in where they could set up the scanner, to gain the best vantage on the bears in the various places they were feeding near the falls. The prime viewing spot for park visitors has a boardwalk access to a raised observation platform near the falls. This platform was very much for safety’s sake, as you do not want to get close to bears, but it also provides an improved view. By setting up brackets on the corners of the platform to hold survey rods for spherical scanning targets, the team could move the scanner around anywhere within view of both the targets and the river, and be assured of high fidelity registration of each scan, and therefore consistency with any other scans.

The scanner has a small UI screen for operation, but to provide more flexibility, the team connected (via WiFi to the scanner) a survey field data collector, a Trimble TSC7 (a Win 10 based device with a 7-inch screen). This made operations in the harsh climate easier than working from the small on-board UI. They were able to look at preliminary views of the “point clouds” to see what they had captured, and if they might need to scan the bear again. With the improved procedures in place, Cusick and his colleagues performed multiple scans of what appeared to be the largest bears.

Measuring the 3D mesh of Bear 32 (Chunk) as modelled in Trimble RealWorks

There are several dozen bears that frequent the river around the falls, some of the biggest are quite well known to web cam viewers and voters in the annual competition. There are no tags on these bears, and they are identified by physical features and behaviors. For instance, Bear 747 has a habit of feeding while sitting on his ample behind. The final determination of each bear’s identity is up to Tammy Carmack, Katmai National Park and Preserve Bear Monitor. Cusick says most of the scans are of the left sides of the bears, as the bears often face upstream to intercept Salmon that are stacking up at the base of the falls, or intercept dead, dying salmon drifting downstream (at the time of year of Fat Bear Week). But sometimes a bear will stand on the lip of the falls, facing the other way and exposing their right side. Often only one side can be scanned, but there is usually enough laser returns to capture the bulk of the bear including the length-wise midline of the bear and the most significant part of the bear – the belly and butt.

The process

“When we survey these bears, as you know, the TLS technology doesn’t produce weight, it doesn’t peer inside a body, it produces a surface and a 3D model from which we can determine surface area and then volume in cubic feet,” he says. “Then it’s up to the biologists to convert to weights using percentages of fat and water densities. There is no easy formula for a density of a bear so this is where “more research and calibrations with live bears say in captivity will have to come into play for better interpolation of size to weight.”

Cusick install pole mounts for one of the tree scanner reference target spheres on the observation platform above Brooks Falls.

Each scan was processed in Trimble RealWorks, a desktop application for processing and analyzing scan data scan data that normally is for buildings, highway and other stationary structures. The point cloud is registered to the scan target spheres, that appear quite distinctly in the scans and algorithms determine the center of each 230-millimeter sphere from any vantage point. The point cloud is cleaned up to remove outliers, or other “ghost” points like the remnants of say a bird that flew through the view. The bear’s furry coats provided surprisingly good laser returns, and at such relatively short ranges, under 150 feet, the point clouds were well defined. Except for perturbations from the bears movement during a brief scan, the processed point clouds made for fairly smooth 3D meshes.  These meshes provided a good medium for determining surface area, and volume by extension.

“We also utilized the 2D measure and cutting plane tools, the latterproved to be inadequate for measuring girth on a bear that moreresembles an oblate spheroid,” Dan Butvidas, who assisted Cusick on themeasurement team, says. “The bears need their own coordinate system, ifwe were going to use cross sections and summarize line segments intotrue distances.”

Cusick concurs, “A ‘Bear Coordinate System’ needs further exploration.” As the estimations of weight has a lot of variables, estimated water content and fat content, he says there was less emphasis on weight this year, and more on surface area. “We processed and compared scans, and our numbers clearly showed which werethe largest,” he adds. “And it was 747 on top.”

One of the summary worksheets comparing values derived from the scans (estimated weights in pounds)

The competition is by vote, and people mostly use photographs to make their choice, but not always. “This is a single elimination, in brackets. They start with 12 or more bears and it’s a single vote for which of two bears appear to be fatter, and then on to the next pair. Some people look at a picture from, say June, and then compare to a September photo to see which appears to have gained the most weight. It is not always what is the biggest bear, a lot of people know these bears so well, and there’s definitely some fan favorites out there. Old bears that have been around for a long time, including one that is called Otis, bear number 480. People really enjoy watching this bear year after year,” he says.

While Cusick and his NPS colleagues have other work to do at the park, when it comes to time on the platform, patience is key. “Once the scanner is initialized, and referenced to the spheres, then I’d sit around and wait to see which bears we could scan and what positions they were in,” he says. “But we did get to save a lot of time and headaches over last year’s method; having to set up on the same point each time and levelling up over the point. With targets we could reattach to poles preset in the brackets, we could set up anywhere in view and be ready to go. This was fortunate this year as sadly with COVID considerations I was not able to bring my surveyor out to the park with me this time.”

Alyssa Reischauer (left), National Park Service biologist (and the teams boat driver), and Cusick (right) performing scans on the bears from the observation platform.

They could sometimes scan several bears in a few hours on the platform, and/or multiple scans of the same bear. With most of the bears being from 70 – 110 feet away when scanned, the bear would have to remain still from 3 – 11 seconds as the beam passed over them.  The number of points ranged from 10,000 to 40,000 points.

What about the possibility of using a drone, to circle the bear from above to get the whole shape? Cusick says that would not be allowed because of the noise and distraction. And it is common that in places like parks and reserves, there are some tight rules regarding drones, with a few exceptions for situations like fires or search and rescue. A static, high-precision and high-speed scanner appears to be the right solution for this kind of endeavor.

“The consensus, among several of the NPS biologists I’ve had discussions with about these scanning activities,” says Cusick, “is that this technology may someday prove useful to monitor growth rates in bears or other species exposed to different management regimes or anthropogenic stressors such as development or climate change. Our efforts are a first attempt to develop these methods for use in future scientific studies.”

“Our efforts are a first attempt to develop these methods for use in future scientific studies.”

The observation platform for public viewing of Lower Brooks River, and the bears!

Several people who performed or supported this year’s bear scanning definitely deserve a shoutout. “Dan Butvidas, he was the guy behind the scenes, a surveyor and his title now is geospatial expert with Trimble. Alyssa Reischauer is an NPS biologist, and our boat driver. Our assistants were Mike Anderson, the former manager of a fish weir at Karluk on Kodiak Island Kodiak, a good guy to have in the field, and Jacqueline Carney, who is also our cook, is priceless in remote field work,” Cusick says.

These brown bears are close cousins of Grizzly bears, considered by some as a sub-species (U. a. horribilis) of the brown bear, and another sub species the Kodiak bear (U. a. middendorfii); They are also cousins of Polar bears (Ursus maritimus). Kraft says, “Many taxonomists consider brown bears and grizzly bears to be the same species (Ursus arctos). With the difference between the two being somewhat arbitrary. In North America, brown bears are commonly distinguished by their access to coastal food sources such as runs of salmon, while grizzlies reside further inland. Brown bears being the larger of the two. Also, these very well could rank as one of the largest BROWN BEARS or at least on par with Kodiak Brown Bears.”

These rising star Katmai Park bears are good representatives that the public can enjoy and appreciate via the web cams, and this annual event.

The voters have spoken in 2020: all hail Bear 747! And the science agrees.