While killer whales are frequently found in Glacier Bay waters, they are more seldom seen than humpback whales. Their movements are much less predictable than humpbacks, making a sighting of this species all the more difficult. Researchers photograph the dorsal fin and gray ‘saddle patch’ just below the dorsal fin because these features have unique markings that make each individual identifiable. By comparing photographs over time, researchers are able to patch together data that illuminates the killer whales’ movements, ranges and life histories. Photographer: Sean Neilson