Cusick was taking a break from work, standing on a platform alongside the Brooks River in Alaska’s Katmai Nationwide Park and Protect — a world-famous spot for bear watching, as the enormous mammals prefer to wade within the water to hang around and catch fish. Otis was just a few hundred ft away, standing comparatively nonetheless.
Cusick, who works for the Nationwide Park Service’s Alaska regional workplace, creates maps and trains individuals on GPS and using scanners within the discipline. He usually makes use of a laser scanner — particularly, a terrestrial lidar scanner — to measure the amount of stationary objects within the park like buildings and gravel piles. It is a $70,000 industrial-grade software that sits on a hefty tripod. That night, Cusick aimed it at Otis, and took a scan.
Lidar is brief for “gentle detecting and ranging” and might be finest identified for its use in autonomous automobiles. A lidar scanner sends out hundreds of thousands of pulses of infrared gentle and measures how lengthy it takes for them to return after hitting an object, similar to Otis. These measurements type some extent cloud that may then be used to construct a three-dimensional map of the thing.
In a matter of seconds, Cusick might see what regarded like pinpoints comprising Otis’s rear on a pill linked to the scanner. Pc software program later processed the scan, making a 3-D mannequin that might be used to find out the width of the bear’s behind.
Cusick was excited; he did not suppose his experiment would work.
“I used to be like, ‘Wow, I obtained a return — I can measure the butt of Otis right here!'” he recalled with a chuckle to CNN Enterprise this week.
It’d sound less complicated to make use of a scale to weigh bears, but it surely’s impractical within the wild, the place it would get chewed on. (Plus, you’d should lure the bears onto the dimensions and get them to face nonetheless for about 11 seconds or so.) In spring, bears within the wild could also be weighed by biologists who fly in through helicopter, tranquilize the bear, push it right into a web, and carry it through a pulley system. However, along with its intrusiveness, the tactic is probably not attainable in fall, when bears have fattened up for the winter.
“An enormous, large upside of this technique is it is noninvasive; we do not have to seize animals,” mentioned Lindsey Mangipane, an Anchorage-based polar bear biologist for the US Fish and Wildlife Service. “It is quite a bit much less logistically difficult for us as effectively.”
Estimating a bear’s weight with lidar is far much less disruptive, although it is nonetheless very a lot a sophisticated guessing sport. As an example, these taking the scans are solely in a position to seize a part of the bear, as a result of there isn’t any strategy to put a scanner on the opposite facet of the river, Cusick mentioned. To make up for this, they might slice a bear scan in half and double the amount of the extra full facet of the physique to estimate the overall quantity of the bear. And whereas a 3-D scan can be utilized to find out the bear’s quantity (how a lot house it takes up, in three dimensions), it would not infer something about its density, which is required to assist determine how heavy it’s.
To get guess at density, which can fluctuate from bear to bear relying on gender, bone construction, time of yr, and plenty of different elements, Cusick spoke with biologists who examine the animals. They figured it could be affordable to estimate a bear is made up of 60% water and 40% fats, he mentioned, so he and his colleagues used these percentages in 2019 and 2020 to tease out, from the scanned volumes, estimates of the weights for numerous bears at Katmai.
The general course of requires a number of individuals, Cusick mentioned: one individual performs the scan whereas one other verifies the bear’s identification, for instance. The burden estimates, which for a single bear could also be made with quite a few scans, are additionally made independently by separate individuals and in contrast.
It is at the moment not possible to know the way correct this technique is, however Mangipane is hoping to validate the scanning expertise by partnering with zoos to scan captive polar bears, whose weights are identified since they are often skilled to step on scales. These identified weights might be in contrast with weights derived from 3-D scans of the bears.
Whereas it will likely be not possible to know for certain which bear is actually the fattest this yr, Cusick thinks 747 appears the most important as soon as extra.
“All of us have our favorites,” he mentioned. “The anthropomorphism right here is kind of robust.”