The boy is shown vomiting, both graphic audio and visual.
A porcupine shoots quills into Brian's leg after he kicks at it, thinking it a raccoon. The next day he's seen groaning in pain as he pulls the quills out of his bloodied leg.
The boy briefly wrestles with a huge bear in the river; the bear runs off after the boy wades too far into the water.
A boy holds out a self-made spear to protect himself against a bear and the bear runs into it; its injured fur is shown with a brief blood spray before it wanders off into the dark (later it's strongly implied the bear died).
A man has a heart attack and dies while flying a plane, which crashes into a lake and leaves the young boy to fend for himself.
The body of the pilot when Brian goes to get the survival kit out of the plane may frighten young children, as the face is partially missing around the eye from decaying underwater.