The researchers randomly dug 662 pits along 32 stretches of shoreline on northern Knight Island, one of the earliest and worst affected areas during the spill. They found Exxon Valdez oil at 14 of the 32 sites. Although oil was spread throughout the tidal range, about half of it was found in the low tide zone, where predators could encounter it while searching for prey. More than 90 percent of the surface oil and all of the subsurface oil was from the Exxon Valdez, Short says.
Based on these findings, the researchers estimated that in a given year, a sea otter ?digging three pits a day searching for clams and other prey ?would probably come into contact with Exxon Valdez oil at least once every two months. However, sea otters dig thousands of pits a year, and Short suspects they actually could be encountering oil far more often than estimated.