Young cub 50 feet up in a tree. Cubs learn very early on to respond to certain vocal signals (like "huffs") from their mothers. One signal tells them to immediately get up a tree as high as they can go (like this), another tells them to come down, and one signal means "Come to me NOW!"
Polar bears use similar signals, including one that means "Stay right there silently until I release you" (used while the mother waits by seal breathing holes); in Spitsbergen last year, we watched a mother polar bear put two cubs in that sort of "wait" position where they sat nearly motionless for 1/2 hour while she lay on the ice at a seal hole 30 yards away. Cubs' ability to follow their mothers' commands like that can literally be a matter of life and death.
This is not a very clear photo, but he's at least half a mile away, and there are limits to camera lens capabilities!