Read this excerpt from Island of the Blue Dolphins. (http://www.alanbrown.com/JustForKids/Previews/Preview116.html)
There are no trees on the island except the small ones stunted by the wind. When a log came ashore, as happened once in a long time, it was always carried to the village and worked on where a chance wave could not wash it away. That the men were sent to hollow out the log in the cove, and to sleep beside it during the night, meant that they were there to watch the Aleuts, to give the alarm should Captain Orlov try to sail off without paying us for the otter skins.
Everyone was afraid he might, so besides the men in the cove who watch the Aleut ship, others kept watch on the camp.