"Walking Hibernation" by Joanne Merriam

In "Walking Hibernation", Joanne Merriam blends science, fantasy, passion, and whimsy.  Jennifer brings her son Don on a tundra buggy tour to observe the polar bears of Churchill.  The powerful creatures harbor a dark secret.  When her son's life is threatened, Jennifer draws on her unusual past to challenge the beasts. 

The story starts off grounded in reality.  The polar bears lay about and the tourists snap pictures.  The timeline then flits around, providing some extraneous background that interrupts the pace of the story.  When we return to the tundra, reality has been usurped by fantasy and the plot takes one twist, then another.  Since I adore polar bears, the story drew me in right away and the twists kept me entertained to the end.