Icky intestines

Science World, March 28, 2005 by Jeanna Bryner

Biologist and wildlife photographer Todd Pusser got quite an eyeful when he motored up in his boat to this marine "crime scene." In California's Monterey Bay last spring, Pusser snapped a photo of a killer whale, or Orcinus orca (OR-sin-uhs OR-kuh), gliding along next to the intestines from its recent kill--a gray-whale calf (young).

Does Pusser's snapshot represent typical orca behavior? For some orcas, the answer is yes. Scientists have identified three orca groups in the North Pacific Ocean: residents, offshores, and roaming transients. The residents and offshore orcas keep to well-defined home ranges and feed mainly on fish. "Transients specialize in feeding on marine mammals (warm-blooded animals with a backbone, whose young feed on milk) such as sea lions, dolphins, and whales," says Pusser. "They rarely, if ever, eat fish."

Usually, the 8 meter (26 foot)-long female orcas are the hunters. And to successfully battle a 6 m (20 ft)-long gray-whale calf, the female transients must team up. "The adult females take turns ramming the gray-whale calf and leaping onto its back, trying to drown it," explains Pusser. This battle can take hours before the calf succumbs. Then, it's mealtime.

"[The orcas] appear to first rip out the lower jaw and throat of the gray-whale calf and eat the tongue," he says. Then, the orcas dine on the calf's blubber, or a thick layer of fat. "The killer whales will grab the blubber with their teeth and pull backward, peeling the blubber from the carcass much like we might peel a banana," Pusser explains.

And do they eat the gray whale's slimy intestines? After Pusser took the photograph, a pair of killer whales pulled the floating intestines beneath the water's surface. He says: "I have to assume that they ate the intestines underwater, though we will never know for sure."