This research helps ocean scientists solve a mystery of what the "offshore" population of killer whales eats. Killer whales have three distinct groups, "resident" fish-eaters; "transient" mammal-eaters; and "offshore" whales, the most mysterious of the three. Many marine biologist consider the three groups as separate species in need of individualized conservation strategies.
Because they feed hundreds of feet beneath the surface, "offshore" orca's diets had been a matter of speculation. Only two feeding events were witnessed between 1988 and 2009 Though the researchers did not directly witness the whales feasting on sharks deep in the briny gloom, they did find chunks of pink shark meat on the surface after observing the whales engaging in feeding behaviors, like quick turns and long deep dives. Genetic analysis confirmed that the meat came from at least 16 Pacific sleeper sharks (Somniosus pacificus).
IMAGE 1: Killer Whale (Orcinus Orca), Vancouver Island, British Columbia, Canada. Credit: Chris Cheadle/All Canada Photos/Corbis.
IMAGE 2: A 30-foot sleeper shark, the largest flesh-eating shark ever photographed, submerges a one-meter bait cage into the ocean floor mud. Credit: Ralph White/Corbis.
IMAGE 3: Orca body types (Albino.orca; Wikimedia Commons) Type A – Physical description: "Typical" killer whale, a large, black and white form with a medium-sized white eye patch. Habitat and Diet: Open water; feeding mostly on minke whales. Type B – Physical description: Smaller than Type A. It has a large white eye patch. Most of the dark parts of its body are medium gray instead of black, although it has a dark gray patch called a "dorsal cape" stretching back from its forehead to just behind its dorsal fin. The white areas are stained slightly yellow. Diet: Mostly seals. Type C – Physical description: smallest type and lives in larger groups than the others. Its eye patch is distinctively slanted forwards, rather than parallel to the body axis. Like Type B, it is primarily white and medium gray, with a dark gray dorsal cape and yellow-tinged patches. Diet: Antarctic Cod. Type D – Physical description: Extremely small white eye patch, shorter than usual dorsal fin that curves back, and bulbous head. Habitat and Diet: Appears to be circumglobal in subantarctic waters between latitudes 40°S and 60°S. Diet: Unknown; presumed to be fish.