Midden contents show that the main source of protein was tuna and dolphin. With the loss of the trees, there was a sudden drop in the quantities of fish bones found in middens as the islanders lost the means to construct fishing vessels, coinciding with a large increase in bird bones. This was followed by a decrease in the number of bird bones as birds lost their nesting sites or became extinct. A new style of art from this period shows people with exposed ribs and distended bellies, indicative of malnutrition, and it is around this time that many islanders moved to live in fortified caves, and the first signs of warfare and cannibalism appear.