After around age 35, female orcas lose the ability to have kids, but they can stick around for another 50 years or more. (Most male orcas, on the other hand, have gone to the great salmon feast in the sky by age 50.) Maternal leaders lend valuable experience to their relatives, the scientists say, mimicking the so-called grandmother effect seen in humans. Offering her lifetime of knowledge, grandma can increase the survival of younger members of the group.
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.