Scientists fear Polar Bears could go extinct more quickly than expected after discovering the world's largest carnivore needs more food than the rapidly warming environment can provide.

The US Geological Survey (USGS) and University of California at Santa Cruz study published in the journal Science followed nine Polar Bears for three years.  Researchers determined each required to ingest at least one adult, or three juvenile, Ring Seals every ten days to sustain them. 

But Global Warming is causing the Arctic's sea ice to recede more and more during the summer, and that's making it difficult for the bears to hunt.  Five of the bears were not able to catch seals at that rate and lost as much as 20 kilograms of their body weight as a result.

"We found a feast and famine lifestyle - if they missed out on seals it had a pretty dramatic effect on them," said USGS biologist Anthony Pagano.  "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.  This and other studies suggest that polar bears aren't able to meet their bodily demands like they once were," he added.

The new report "fills in a lot of missing information about polar bears," said Polar Bear researcher Dr. Stephen Amstrup, who was not involved in the USGS research.  "Every piece of evidence shows that polar bears are dependent on sea ice and if we don't change the trajectory of sea ice decline, polar bears will ultimately disappear."

Arctic sea ice has declined by around 13 percent during each decade since 1979.  Last year was the eighth lowest minimum extent in the 38-year satellite record.

A few weeks ago, "soul-crushing" video of an emaciated, dying Polar Bear scrounging for its last morsels of food went viral across social media.  Photographer Paul Nicklen of the environmental group Sea Legacy said his team "was pushing through their tears and emotions while documenting this dying polar bear".  The animal shows the horrible choice that many Polar Bears have to make:  Leave land and follow the ice out to sea, where food is scarce; stay on land and try to make a living on small mammals, goose eggs, and garbage in far-flung arctic towns - which means more potential for disaster because of increased contacts with humans. 

"This is what starvation looks like.  The muscles atrophy.  No energy.  It's a slow, painful death," said Nicklen.  "The simple truth is this - if the Earth continues to warm, we will lose bears and entire polar ecosystems," he added, "We must reduce our carbon footprint, eat the right food, stop cutting down our forests, and begin putting the Earth - our home - first."