Shadow Bear by Joan Hiatt Harlow
I love this gentle story of an Eskimo boy and a polar bear cub. Written as parallel tales, the boy's mother warns him about the large, dangerous bear while the cub's mother warns him about dangerous humans.
Both young ones go out for a romp on the tundra and carefully peek around a large boulder. The low, setting northern sun casts huge shadows, even of a small boy and a small cub.
Each is reminded of his mother's warnings and runs home where it is safe.
I am hesitant to tell you about this book because it is out of print. But hopefully your library has it or you will be lucky enough to find it at a used book sale. If you do, enjoy!