Male killer whales "do not live as long as females and have fewer opportunities to obtain information about the environment," Brent said. "This difference in life experience may force males to be more reliant on the ecological knowledge of older females."
Based on 750 hours of footage, filmed over a 9-year span by orca expert Ken Balcomb and the Center for Whale Research, the researchers could identify which orcas regularly swam at the head of the pack. Earlier studies indicate that animals at the front, Brent said, "exert greater influence over the movement of those groups."
Matriarchal guidance is particularly important when food is scarce - which Chinook salmon often are for orcas who live year-round in the Pacific Northwest.