Number of polar bears to fall, courtesy climate change

A new study by researchers at the University of California, Los Angeles (UCLA) has revealed that polar bears aren't suited for southern diets and their numbers are likely to dwindle as climate change forces them south.

 

As polar bears lose habitat due to global warming, these biologists say, they will be forced southward in search of alternative sources of food, where they will increasingly come into competition with grizzly bears.

 

To test how this competition might unfold, the UCLA biologists constructed three-dimensional computer models of the skulls of polar bears and grizzly bears - a subspecies of brown bears - and simulated the process of biting.

 

The models enabled them to compare the two species in terms of how hard they can bite and how strong their skulls are.

 

"What we found was striking," said Graham Slater, a National Science Foundation-funded UCLA postdoctoral scholar in ecology and evolutionary biology and lead author of the research. "The polar bear and brown bear can bite equally hard, but the polar bear's skull is a much weaker structure."

 

The implication is that polar bears are likely to lose out in competition for food to grizzlies as warmer temperatures bring them into the same environments, because grizzlies' stronger skulls are better suited to a plant-rich diet, said Slater and Blaire Van Valkenburgh, UCLA professor of ecology and evolutionary biology and senior author of the research.

 

"The result for polar bears may be lower weight, smaller and fewer litters, less reproductive success, fewer that would survive to adulthood, and dwindling populations," Van Valkenburgh said.

 

The research was published this month in the online journal PLoS ONE, a publication of the Public Library of Science.