However, these technologies were not created to be used on polar bears in minus 30 degrees Celsius conditions, so it took several years to collect the information that we were seeking.
The GPS told them the distances the bears wandered, and the video camera recorded if the bears were successful in killing and eating prey.
While the recent study might be bad news, it doesn't automatically mean the end for polar bears, comments Jörns Fickel, a evolution geneticist at the Leibniz institute for Zoo and Wildlife Research in Berlin.
"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. "This is what a starving bear looks like". There, Arctic warming means the sea ice is breaking up earlier in the summer and returning later in the fall, forcing bears to spend more time on land.
Alarmingly, five of the nine bears being monitored lost body mass while they were being monitored, meaning the animals were not catching enough prey to meet their energy demands. For more than a decade, San Diego Zoo Global's researchers and its USA and Canadian partners have focused on contributing to science-based conservation strategies, to preserve and understand wild populations of polar bears.More news: Larry Nassar victims' father attacks in court
"You're talking a pretty fantastic amount of mass to lose", said U.S. Geological Survey wildlife biologist Anthony Pagano, lead author of a new study in Thursday's journal Science. When we recovered them, we had collected eight to 11 days of footage showing polar bears' behavior on sea ice from a bear's point of view, which we could link with the animals' energy expenditures.
The data showed the bears were active about 35 percent of the time and resting for the remainder, yet they burned through 12,325 calories a day, much of it from their body reserves. The researchers could compare this with the bears' activity and hunting success. One bear lost 51 pounds (23 kilograms) in just nine days. By the fall, the young seals are older and wiser, and polar bears are not able to catch as many.
Satellite telemetry shows several tagged polar bears moving long distances to remain on receding sea ice in July 2016. In fact, four of them lost at least 10 percent of their weight in the span of about 10 days. It has been hard, however, for researchers to study the fundamental biology and behavior of polar bears in this very remote and harsh environment, Pagano said.
Most of the time the bears tracked in the study did use the "sit and wait" technique.
Previous studies had tried to estimate polar bear metabolic rates and energy expenditures based on some assumptions about their behavior and physiology.
The huge glacial ice sheets in Greenland and Antarctica are reacting more slowly to the warming atmosphere and oceans but scientists are watching them closely as they will heavily influence sea level rise if there's significant melting.
Photos of skinny and emaciated polar bears are more common as their food disappears
Unfortunately, with the rapid environmental changes occurring in Arctic sea ice, the specialisation that once allowed polar bears to live in this challenging habitat has painted the animals into a physiological corner and led to devastating consequences.