Continuity mistake: When Carl offers the Nestles chocolate to the native girl, the wrapping differs between shots as he holds it out to her.
Factual error: In at least one shot as Kong is on top of the Empire State building, the sunrise over Long Island is wrong. Three planes attack from the southwest and we see the sun rise in the east as Newtown Creek (Nassau River) glistens across the East River. The mouth of this river opens southward but in this shot everything is inverted with the mouth of the river pointing northward. Also, looking eastward, Roosevelt Island should be on the left of Newtown Creek, not on the right.
Continuity mistake: On the cliff where Ann is entertaining King Kong by dancing, juggling, doing flips, etc. her face goes from dirty, to clean, to dirty, and back to clean between shots.
Factual error: When Denham sees the smashed camera he sees the film stock spilled on the ground. It is brown, indicating unexposed colour stock. Brown emulsion film didn't exist in those days - it was introduced by Kodak in 1943. In those days it would have been black and white emulsion, blue on one side, and grey on the other. Colour films in the early 30s were made by painting black and white films frame by frame or printing the monochrome negative three times and staining each one a different primary colour.
Continuity mistake: At the end of the chase through the streets of NYC, Kong stops the yellow cab with a "karate chop" to the front-end, which sends the car tumbling high into the air through a complete somersault before it lands back down. Actually, Kong's hand is still half way down and nowhere near touching any portion of the vehicle when its rear-end gets lifted.
Factual error: There is no lift in the Empire State Building running between 1st and 100th, as shown on the dial in the lift.
Continuity mistake: When Jack is rescuing Ann she has two cuts above her right eyebrow, the smaller cut changes positions and disappears/reappears in different shots.
Factual error: The drop fare on the taxi is shown as 25 cents. However, this fare was not charged until 1952, when the former taxi fare of 20c 1st 1/4 of a mile and 5c each additional 1/4 of a mile (which went into effect in 1934) was increased to 25c the 1st 1/5 of a mile and 5c each additional 1/5.
Factual error: In the scene where Kong is running around the streets of New York City and being chased by two military vehicles, the lead open-topped sedan has an air-cooled 30 caliber machine gun mounted on a bar behind the driver, with the gunner in the back seat. The time setting of the movie is 1933-1934. Air-cooled ground mounted machine guns were not in general use until 1942, and were not available for aircraft until 1936. The Army used water-cooled machine guns until the start of World War II.
Continuity mistake: When Kong falls through a portion of the circular observation deck at the top of the skyscraper, he crushes the metal siding as well as one of the metal girders, making a large hole. When he puts Ann inside through the hole, the metal girders are now all undamaged. You can tell that this is the same hole because the camera moves around the entire building in the next shot and there are no other large holes.
Continuity mistake: Just before the wall is spotted, Jimmy is in the open crow's nest reading "Heart of Darkness". He puts the book down and stands up. In the next few shots, the book has completely disappeared. Then the ship takes a pounding for 3 or 4 minutes. But a few minutes later there's Jimmy, once again reading the same book. (00:46:05 - 00:54:15)
Audio problem: After the scene where the men had to fight off the giant bugs, there is a wide shot where the men can be seen being helped out of the pit by the captain and a few extra crewmembers. The captain is shouting something, however, if you look closely, his mouth is not in sync with what he is saying.
Continuity mistake: Shortly after Kong realizes he's been shot and gets blood on his fingers by touching the bloody hole in his chest, in subsequent scenes his chest has no puckered indentation and is unblemished but for minimal straight-line scars.
Continuity mistake: When Carl falls at the beginning of the brontosaurs chase we see that he is only just in front of the brontosaurs so when he fell he should have been crushed straight away but he isn't. Jack then runs to help him and we see that the brontosaurs only need another step or 2 (which would take 1 or 2 seconds) before they reach Carl and Jack. Carl gets up and argues with Jack for 5 seconds or so by which time they should have been crushed. They then run and there is a far off shot showing the brontosaurs back where they were at the start again.
Continuity mistake: Ann is soaking wet when she is being led through the natives. When she gets to the top of the wall she's dry.
Continuity mistake: When the Skull Island natives are holding Ann's arms as the old native taunts her, their grip on Ann's arms and sleeves differ between front and back shots.
Revealing mistake: When Carl is standing next to Kong's unconscious body saying, "His name will be in lights on Broadway," look at the Venture in the background. Even though it's not stuck on anything, and despite the choppy waves, it doesn't move ANY. Even if anchored, it would still bob gently in the waves; instead it's frozen solid. Obviously green-screened, or possibly a matte painting. (02:17:40)
Continuity mistake: When Carl and his assistant are driving in the cab discussing who to fill in on the female role, you can see that they pass a tram on their left side. When it cuts the cab is right in front of the tram rather than to its right.
Continuity mistake: When Carl is convincing Ann inside the diner, after she stands up and Carl convinces her to accept the role, there's a waitress behind Carl about to walk towards her. A split second later, while Carl says "she's the saddest girl he's ever met", the waitress appears 12 feet away, and is now behind Ann way at the end of the diner.
Audio problem: When Carl tells Preston to show Ann on board the ship he says something like, "Hello, Miss Darrow, I'm Mr. Denham's assistant." His lips aren't properly synchronized with the dialogue when he says this.
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.