Alaska’s ‘Fat Bear Week’ isn’t just fun and fun
Brown bears put on weight for winter hibernation in Alaska Katmai National Park and Preserve. And from Wednesday, thousands of viewers around the world began to tune in for Fat Bear Week to watch the bears gobble up the fish from the Brooks River, estimate how much they pack, then vote for the biggest in a single elimination round.
But how big are these big bears? A winner will be crowned on October 5, but webcam viewers – nearly 650,000 votes cast last year – and real visitors – 15,000 came to Brooks Falls to see the bears in 2019 – are just guessing. However, there is hope to achieve greater precision: GIS Specialist Joel Cusick is developing a new technique for calculating bear weights that has broader implications for non-invasive 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 in Katmai. A terrestrial lidar scanner, which uses lasers to determine distance and other measurements, was available to measure buildings. It’s the device traditional civil engineers use, but when Cusick made his way to Brooks Falls and stood on a viewing platform 300 feet from the bears, inspiration struck. He was thinking: Why not use the scanner to measure a bear’s surface volume instead?
“I had laser feedback from the butt of Otis, one of the most famous brown bears out there,” Cusick says. “I was thinking, Wow, that might work out well. “
Lidar, which stands for “light sensing and ranging,” emits beams of light to measure three-dimensional objects or areas. When light waves hit an object, they bounce back and return to the sensor. Computers then use the speed of light to calculate the distance between the sensor and all the points. This figure is processed using software capable of modeling an object in three dimensions. Scanners have become standard technology that is deployed ground, sky and satellites to measure vegetation growth. Now they are used to measure the length, height and girth of bears.
And bears like Otis, a legendary former Fat Bear Week champion, are actually quite suitable for lidar scanning. Katmai bears are usually weighed in the spring, when they are lighter, using a pulley system. However, the process is resource intensive; it usually involves a helicopter and requires the bear to be tranquilized. The 4.1 million acre park in southwest Alaska (home to more than 2,000 bears) is already isolated and mostly accessible only by air. “In the fall, the weight of these bears has always been a big mystery because they just can’t weigh them,” says Cusick.
The devices only need three to 11 seconds to pass over the animal; given that the bears are currently preoccupied – fishing for salmon swimming upstream to return to the spawning grounds – they stay relatively still while they wait. “I didn’t expect them to be as still as they were,” Cusick says, and describes them as “standing like statues”. Initially, it seemed that their thick fur could prevent the laser from penetrating enough to be precise, but the damp environment and haze cover it enough to get a good reading. If they are partially submerged, however, this becomes a challenge; the laser cannot sweep in the water. Also, Cusick needs to get a good record of the bears’ bellies, which are full of fish, berries, and other foods. “If we can get their belly to swing right above the water, that’s the biggest percentage of their volume and that’s what we’re hoping for,” he says. “It’s a lot of patience, standing like a photographer, waiting for a perfect shot. We do the same with lasers.
Inspired by his success, Cusick returned in 2019 and 2020 with a more accurate and faster scanner. His work confirmed that people voted for the biggest bear. Last year: Bears 747. (Bears are numbered by the park for research purposes.) The winner’s volume was 22.6 cubic feet, or about 1,416 pounds, compared to the finalists, who followed the aptly named 747 to 1 250 lbs – Bear 32, or “Chunk” and the 1212 lbs Bear 151, or “Walker”. The internet sensation humbly began in 2015 as a National Park Service effort to educate the public about bears, which can gain up to four pounds of weight per day preparing for winter, and their surrounding ecosystem.
There is still work to be done regarding the precise conversion of volume to mass. “The trick to getting the mass of the bear is knowing the density in pounds per square inch,” Cusick explains. “This is the part of the equation that is still not determined.” He used a rough estimate to calculate the weight, estimating that bears contain 60 percent water and 40 percent fat.
Big bears are not being scanned this year due to COVID-19 and personnel constraints; Cusick is always accompanied by a “bear instructor” who knows bears. (The vote the process remains the same this year, however.) But other researchers are eager to continue work in their own areas of expertise. “I’m trying to get all of the ‘logs’ I work with to enter the 3D world that is possible with this type of terrestrial laser scanning on the ground,” Cusick explains. “It’s a fast growing technology.
And “logues,” as he calls them – for most bear biologists so far – are interested. “I’m really excited about his work,” says Lindsey Mangipane, polar bear biologist with the US Fish and Wildlife Service. “It shows a lot of promise.”
A recent to study shows that the mass of polar bears is an accurate measure to assess the links between what bears eat and how the population is doing. As the pack ice melts, bears spend more time on land, where they do not have access to their traditional prey, such as ringed and bearded sales.
Mangipane and others are working on a study using captive polar bears in zoos, which are trained to ride on scales and already have a known weight, to assess the accuracy of the scanning method. Scanning would be done throughout the year to ensure that the shape of the bears – how fat or skinny they are – does not skew the results. The tests could start in the year.
If the lidar scan proves accurate for polar bears in captivity, scientists hope to use it as a non-invasive tool in the wild. Less reliable sea ice means the work of biologists has become more dangerous than before. “We used to go and catch polar bears on the ice,” Mangipane explains. “In recent years, the ice was not good enough for us to go out. It is important in the future that we have new ways of getting the data we need to make more informed management decisions.
This message appears courtesy of High Country News.