Due to hunting, sea otters were extirpated from most of their former range, including all of Washington state. In 1969 and 1970 a small group of 59 sea otters from Amchitka Island, Alaska, were reintroduced to the outer coast of Washington state, where they have since flourished to more than 2000 individuals. As their numbers have increased, they have expanded along the coast, resulting in a patchwork of locations containing sea otters that have been present in each location for differing lengths of time and at a range of densities. The resulting gradient of occupation time and density provides a natural experiment that a group of researchers has now used to detect which factors affect sea otter diet. The most important predictor for diet was habitat type; in addition, sea otter diet became much more diverse in areas with high sea otter densities, and total energy intake slowed down in high-density areas. The new work by SAFS PhD student Jessica Hale, SAFS and APL professor Kristin Laidre, and their coauthors, appears in the journal Marine Mammal Science.