Last year, the Polar Bear Specialist Group (PBSG) concluded that out of 19 sub-populations of polar bears, four were declining (all in Canada), five were stable, and one was increasing. There was insufficient data about the remaining nine. In fact, about two-thirds of the world's polar bears live in Canada.
City of Albuquerque on flickr / Licensed under Creative Commons Attribution 2.0 GenericYet, in a September 2014 report by CBC's Reg Sherren, I learned that the scientific community is not in full agreement about their status. And I think the challenging part is getting a complete picture of polar bear populations. With only enough reliable data on just over half of the sub-populations, clearly it would be difficult to speculate on their overall status.
Fortunately, better methods are being employed now. Dr. Seth Stapleton, a University of Minnesota polar bear researcher, developed new techniques for monitoring polar bears via aerial surveys and satellite. In 2011, he estimated polar bear numbers in a large western Hudson Bay region and found 1,030 polar bears (a figure close to the 2004 mark-recapture estimate).
What Makes Polar Bears Most Vulnerable
As hardy as polar bears are, there are glaring challenges that could hugely impact their populations. Dramatic changes in arctic ice floes would make it difficult for them to hunt seals - a mainstay of their diet.
And unlike other types of bears, polar bears cannot live off berries and other plants. As spelled out in Polar Bears International's Myths and Misconceptions:
It’s true that polar bears have evolved to eat seals, but they are opportunistic hunters and if seals are not available because the sea ice is absent, they will eat almost anything. Unfortunately, few polar bears have been observed eating more nutritious foods like birds or eggs, and those foods are not abundant enough or distributed widely enough to be a benefit. Plant foods are just not nutritious enough to compensate for lost seals. Much like a human eating a stalk of celery versus a juicy steak, the nutritional benefit is not the same.
Kristine Paulus on flickr / Licensed under Creative Commons Attribution 2.0 GenericFrom the World Wildlife Fund's spotlight on polar bears, I discovered they "spend over 50% of their time hunting for food, but less than 2% of their hunts are successful.
Their diet mainly consists of ringed and bearded seals because they need large amounts of fat to survive."
As I researched some more, I learned that similar to giraffes, polar bears have one of the slowest rates of reproduction of any mammal. In their lifetime, they only produce about five litters. And they don't have a long lifespan in the wild either - only about 15 to 18 years.
What's even more alarming, a November 17th, 2014 post by the Associated Press in the New York Times stated that researchers found only two out of 80 polar bear cubs tracked between 2004 and 2007 survived. That mortality rate is much higher than I previously thought.
Scientists and researchers are blaming a loss of sea ice (due to global warming) as the reason for the dramatic increase in young cubs starving and dying.
Mother Polar Bears Usually Give Birth to Twins
Single or Triplet Cubs are Less Common
"Our estimations are, if we had a very early melt, and a very late freeze, we could see up to 50 percent mortality in a single year. You put a couple of years like that back-to-back, and things [polar bear deaths] could happen very quickly."
Understandably, it would be difficult to study polar bears in most regions of the arctic. Not only would it be dangerous for vessels because of the climate and weather conditions, but getting close to any mother and her cubs is always risky.
Up next is a short video by Animal Planet of a polar bear cub rescue. Watch as Russian arctic scientists attempt to free a polar bear cub from a fox trap before the mother bear attacks them.
Polar Bear Cub Rescue
Uploaded on Oct 8th, 2008 by Animal Planet
About Polar Bear Cubs
According to Polar Bears International's Polar Bear FAQs, pregnant polar bears dig a "maternity den" in late October or early November. These dens are located in snowdrifts on sea ice, on hills near shore, or in snowbanks on mountain slopes.
polarphotos on flickr / Licensed under Creative Commons Attribution 2.0 GenericMother polar bears and cubs remain in the den for 3 months. The cubs are nourished by mother's milk which is rich at 31% fat.
Incredibly, the mother survives off her own fat reserves during these months - she doesn't eat, drink, or defecate.
The cubs are born blind, toothless, and with only short fur to insulate their bodies. They are completely dependent on their mother for food and warmth.
Polar bear cubs need their mother until they are 2.5 years old. However, some bears in the Hudson Bay area, have been observed to wean their cubs at only 1.5 years of age. It is the mother bear that teaches the cubs how to hunt and survive in one of the harshest environments on the planet.
Up next, senior scientist Doug Inkley, Ph.D. explains why polar bears need sea ice and what can happen to them because of global warming.