A whale of a meal
VANCOUVER, B.C. – Amazing new research into killer whales’ feeding habits demonstrate how they are able to hunt, kill and consume their much larger cousin – the gray whale.
The study—conducted by Vancouver Aquarium research scientist Dr. Lance Barrett-Lennard and a team of colleagues—documented gray whale predation by killer whales near Unimak Island, Alaska.
“Whalers have known for centuries that killer whales can hunt, kill and consume whale species far larger than themselves,” said Barrett-Lennard. “But such events are seen and reported rarely, and it’s been hard to determine how common it is, how the killer whales manage such a feat, and what the impact might be on prey populations.”
Culminating four years of observation, the study—Gray whale predation and prolonged feeding on submerged carcasses by transient killer whales at Unimak Island, Alaska (Lance G. Barrett-Lennard et al. )—describes the behavior of a newly-discovered population of killer whales at the boundary of the Pacific Ocean and Bering Sea.
The research team made the following discoveries:
• Over 150 transient killer whales gather every spring near Unimak Island, Alaska, when gray whales are heading north on their annual migration.
• For a month or more, the killer whales hunt and feed exclusively on gray whale calves and yearlings.
• The gray whales’ principal defense is to move into very shallow water along the shoreline, where killer whales are reluctant to press the attack. The killer whales also give up when mothers defend their calves particularly aggressively.
• Most gray whales are attacked in waters of 10-20 m depth and sink to the bottom after death.
• After an initial feeding period, killer whales leave the site for 24 hours or more before returning to feed again—the first time such food storing behavior has been reported in whales.
• Stored carcasses leave a tell-tale sheen of oil on the surface that may persist for up to a week.
• Gray whales killed by killer whales provide an important source of food for other predators, including Alaskan brown bears and sleeper sharks.
“Through direct observation, we’re beginning to recognize the dramatic impact killer whales have on other aquatic life,” says Barrett-Lennard. “For example, we estimate that killer whales take up to a third of the calves born to the Eastern Pacific gray whale population each year