
Continuity mistake: When Ann is dragged around by the natives, the one on her left sinks her head down, while his left hand grabs her arm. An instant later, both of his hands are clinging to her arm.

Continuity mistake: When Ann meets Kong on NYC street, the camera flashes back and forth between them. When it shows Kong, he is surrounded by snow, but when it shows Ann, the street doesn't have so much as a snowflake.

Continuity mistake: Jack and Carl are in Carl's stateroom. Carl opens the crate of whiskey, takes out a bottle and puts it down. The bottle then turns itself around so the label's sometimes visible, sometimes not.
Answer: They scared them off with their guns. In the scene where they capture Ann to sacrifice her to Kong, Denham and his men come to rescue her and when they start shooting the natives hide. It's never fully explained but the most likely answer is that they are too scared and have even moved villages or are just hiding really well.