Polar bears are migrating north to colder climates as temperatures rise in their native habitats, a new study reveals. Bears living in Arctic region of North America now appear to be headed toward the Canadian Archipelago.
The U.S. Geological Survey (USGS) led a study of genetic material from polar bears in the Canadian Arctic, collecting 2,800 DNA samples from the animals, in an effort to accurately determine how migrations of the animals changed over time. The oldest of the material examined was collected in 1972, while the youngest samples date to 2011. Biologists in the region have observed bears heading toward colder land in the north, but this study was the first to provide hard evidence for the behavior.
"By examining the genetic makeup of polar bears, we can estimate levels and directions of gene flow, which represents the past story of mating and movement, and population expansion and contraction. Gene flow occurs over generations, and would not be detectable by using data from satellite-collars which can only be deployed on a few polar bears for short periods of time," Elizabeth Peacock of the USGS said.
Biologists currently recognize 19 subpopulations of polar bears based on their territory and oceanographic characteristics. Genetic analysis of the Arctic mammals reveals the animals can be grouped into four main clusters. Researchers have labeled these as the Southern Canada, Eastern Polar Basin, Western Polar Basin, and Canadian Archipelago populations.
Investigators also detected that polar bears have been migrating toward the archipelago for between one and three generations. Males appear to be more likely to venture further away from their native habitat than females. However, radio tracking of male polar bears, using electronic collars, is impossible because their necks are wider than their heads. This is the first time that genetic evidence has ever been found for such a movement northward by the animals.
Polar bears were thought to be the product of hybridization, long ago, with brown bears. That theory is supported by the new DNA analysis.
Sea ice is essential to the life cycle of polar bears, but moving toward such a remote area could pose significant risks for their survival as a species.
"And what can happen when populations of animals become isolated is that they can blink out if something happens; if they have a bad winter or bad spring and that stresses the population and it gets smaller and smaller, but the migration corridor has been cut off and you can't repopulate," Peacock told the press.
Implications of the Circumpolar Genetic Structure of Polar Bears for Their Conservation in a Rapidly Warming Arctic, an article detailing investigation of the movement of polar bears in North America, was published in the journal Plos One.