As a scientist, he stresses that we shouldn't go off of gut feelings, but rather reliable data - "and for polar bears, those (data) aren't there yet".
New research published yesterday in Science adds fuel to those concerns. Scientists have believed that because bears hunt mostly by waiting for a seal to pop through a blowhole, they don't use much energy.
"The other bears either scavenged or they fasted, and they all lost mass", as much as 20 percent of their body mass, Mr. Pagano said.
Polar bears rely nearly exclusively on a calorie-loaded diet of seals.
A polar bear tests the strength of thin sea ice. They recorded dramatic, and at times, bloody seal hunts from the bear's perspective. Then the bear bites it on the neck and drags it onto the ice.
"No sea ice, no polar bears, it's really simple", said Dr. Bechshoft. Because of climate change, the ice is shrinking and thinning more and earlier, he said. Even today, in the middle of the bitter cold Arctic winter, satellites show there is about 770,000 square miles less sea ice than the 1981 to 2010 median (That's an area larger than Alaska and California combined). Or they stay on land longer, spending the summer and, increasingly, the fall fasting, living off their fat from the seals they caught in the spring.
Pagano's team studied the bears in a period during April over the course of three years, from 2014 to 2016, in the Beaufort Sea off Alaska. Global Positioning System video-camera collars were applied to solitary adult female polar bears for 8 to 12 days in April, 2014-2016. They analyzed their blood and urine. One bear had moved 155 miles away by that time. It is more than the previously estimated level of calories that these predators needed to stay healthy. The videos revealed that four of the females weren't able to catch a single seal.
While scientists were quick to caution that the causes of the animal's condition remain unknown-disease, injury or any number of other factors could potentially have spelled its demise-experts are anxious that starving polar bears may soon become a more common sight as the sea ice they rely on for hunting grounds continues to melt away. One bear lost 51 pounds (23 kilograms) in just nine days.
Mr Pagano said the next step was to study what happened to polar bears throughout the year, particularly when the ice breaks up and the bears move further north with the ice.
A high fat diet based on blubbery seals is essential for providing the necessary energy for the bears to live in the cold, but sea ice changes have made it harder to find this critical prey, Williams said. The species is categorized as "vulnerable".
Experts estimate the total polar bear population at between 22,000 and 31,000.
USGS researchers have been studying polar bears in the Beaufort Sea area since the 1980s and have found that polar bear population has declined by 40 percent in the past decade.
"We were surprised to see such big changes in body masses, at a time when they should be putting on bulk to sustain them during the year".
"Two-thirds of the world's polar bears could die out by 2050", cautions WWF, demanding an immediate decline in greenhouse gas emissions so the bears can stand a chance of survival.
In fact, when measured at its September minimum, Arctic sea ice has declined by around 13% per decade since 1979.
'We found a feast and starvation lifestyle - if they missed out on seals it had a pretty dramatic effect on them, ' said a biologist who led the research.
"That [number] tells us a lot about modelling into the future what's going to happen with the bears".
"Spring is the pupping season for the seals", said Dr. Bechshoft.