Polar bears are majestic creatures, growing up to 3 metres tall and weighing between 350 to 700kg in their adulthood. That also means that these white giants need to eat a crapton of food in order to maintain their mass.?
Images courtesy: USGS
In the spring, their major hunting heason, polar bears need to consume over 12,000 kilocalories a day, roughly six times the average human¡¯s requirement. That¡¯s according to new research, which greatly overshoots what scientists thought they previously needed to stay healthy. The problem is, as the Arctic ice continues to melt, these polar bears are having more and more trouble getting all the meat they need.
In the month of April between 2014 to 2016, a team of researchers tracked the activities of nine female polar bears living on sea ice in Beaufort Sea, off the northern Alaskan coast. Aside from analyzing their blood and urine, the team also outfitted the bears with GPS collars and cameras that recorded their movements and meals.?
Their data showed polar bears have a crazy high metabolism, needing to eat at least at least one adult ringed seal, or 19 newborn pups, every 10 to 12 days. If they don¡¯t manage to catch that much, they bears start losing weight drastically, with four of the bears shedding about 20kg in just 10 days, amounting to about 10 percent of their body mass.
The videos the researchers took also show how polar bears hunt. Most of the time, they sit near breathing holes made by seals in the ice, waiting for their prey to poke through. When they can¡¯t catch enough, they lose weight. One bear lost even more than her body fat, she began losing muscle mass too in just 10 days.
So why is this a consequence of global warming? That¡¯s because it¡¯s causing the sea ice to steadily melt, sea ice that polar bears depend on to catch seals. As swift as polar bears are in the water, seals are faster, and polar bears have evolved to hunt them when they come up onto the ice to breathe or rest. Estimates say that, if we keep pumping greenhouse gases into the atmosphere at our current rate, we could lose two-thirds polar bears to starvation by 2050, eventually driving them to extinction by the end of the century.
The thing is, the bears only need to eat that much in spring or early summer, putting on lots of fat thanks to the fat-heavy seal meat. They can then use that body fat to survive through the long winter until the next year. But without enough sea ice to hunt, polar bears have to range further to hunt, using up more energy than putting into their bodies. That in turn affects their health and ability to have cubs. Just in the Beaufort Sea, the number of polar bears has declined by over 40 percent since 2004.