With their striking black-and-white coloring, huge flukes and dorsal fins and their well-known antics at SeaWorld, killer whales are among the must famous ocean dwellers. To marine biologists, killer whales go by the scientific name Orcinus orca ” but that may not be the whole story. Recent studies suggest that there are more than one species of killer whale in the sea.
Bob Pitman, of La Jolla-based Southwest Fisheries Science Center, has spent much of the past two decades studying whales in Antarctica. He had read old reports of different kinds of killer whales in the Antarctic waters, but the evidence was spotty. Pitman decided to see for himself.
“It became evident to me, fairly quickly, that there were in fact three different kinds of whales down there,” Pitman said. “They are quite distinct.”
He calls them Type A, Type B and Type C.
“Type A is a regular killer whale; it looks like Shamu,” Pitman said.
These are the biggest Antarctic whales that travel the open ocean in pursuit of their favorite prey, minke whales.
Type B whales are smaller and have different markings. They are grey, with a darker section, called a “cape,” on their backs. They have a white eye patch much larger than Shamu’s. The Type B whales’ meal of choice is seals.
The seals, of course, can climb onto a floating bit of ice to avoid the whales. So, the Type Bs had to get clever. Scientists have observed the whales using different techniques to get the seals into the water.
“One of them will lift up the edge of the ice and roll the seal off,” Pitman said.
In another mode of attack, the whales rush towards the ice floe at full speed, and turn at the last moment to create a wave that washes the hapless seal into the water.
The smallest are the Type C whales. Like the Bs, they wear a dark-colored cape on their backs. Type Cs have a small, slanted eye patch. They live on the edge of the Antarctic ice, swimming underneath the dense ice in search of their preferred food, fish. Type Cs are often seen “spyhopping “sticking their heads up out of the water. Pitman believes they are looking to make sure there are holes in the ice that they can breathe through.
Pitman has found that the three whale types differ in coloring, diet and habitat. Most recently, he has collected data clearly showing that the Type Cs are significantly smaller than the Type As. This research is in the February issue of the Journal of Mammalogy. However, his studies are not quite enough to prove specieshood.
Normally, a new species is represented by a “type specimen.” Antarctic killer whales are protected, and there are few beaches where animals might become trapped. So, Pitman has been unable to collect specimens that confirm his ideas.
What he needs is genetic evidence. During his most recent Antarctic trips, Pitman has been shooting darts at the whales. The darts collect a sample of skin and blubber, about the size of a pencil eraser, and then bounce harmlessly off the creature. Using DNA from these tissue samples, Pitman hopes to soon have a solid answer about how many species of orcas are swimming around in the Antarctic.
“I’m pretty convinced that when this is over, we’re going to have more species of killer whales,” he said.
As the top predator, killer whales are important players in the Antarctic food web. The possibility of prey specialization makes them even more interesting to scientists. Pitman’s work should help scientists better understand the ecology of the Antarctic.
“The killer whale is an iconic animal,” Pitman said. “It’s a big animal, it’s conspicuous, it’s an air-breather, people have been studying them for decades ” and we don’t even know how many species there are! That, to me, is a clear indication of how little we know about what’s actually going on in the ocean.”