Killer whales cache their catch
February 14th, 2011 | Dimitra Lavrakas
Killers whales off Unimak Island may act like squirrels after they drown a passing migrating gray whale calf or yearling, but at least they have good table manners.
"Sometimes 40 whales can be on a carcass, but generally it's about four to eight that do attacks," said Craig Matkin, biologist for the Homer-based North Gulf Oceanic Society that specializes in marine mammal education, research and conservation.
The killer whales leave the carcass for several days and go back to feed on it. Sleeper sharks also partake and that has caused a rise in their numbers in the area, and also contributed to supporting the brown bear population that scavenge for a meal when the whale washes up on shore.
"A lot of whales feed on it and stay on it for quite a while, but you don't see a lot of fighting," he said. "They share well and they communicate well, but definitely there's hierarchy."
Pursuit of the young grays, usually three to four killer whales, was cut short if they met forceful resistance from the mother. Or if in defense the gray whales moved into shallow waters less than 4 meters deep, the killer whales backed off because they prefer to operate in depths of 15 to 75 meters.
The importance of this research, Matkin said, is to track the health of the Eastern Pacific gray whale population, which was once listed as an endangered species but taken off the list in 1994. Under quotas established by the International Whaling Commission, gray whales can be hunted by the Makah Tribe of Washington state and Native people in Chukotka, Russia. The Russians, he said, take them with factory ships.
But the killer whales just might be making a dent in the gray whale population, Matkin said.
"Gray whale calf production is low and if the killer whales are taking calves we can get a handle on how many and their ages," he said. "They could be taking 70 percent of calves."
The study leads to other questions that biologists have, he said.
"Which animals do most of the killing? Where do killer whales go when they're not in False Pass? " he said. "They do spend more time in the area than we thought, mid-April to mid-June."
As sometimes happens in science, it's a local that points out the unusual from simply paying attention daily to any changes in their environment.
Buck Laukitis, a Homer-based commercial fisherman who's homesteaded in False Pass across from Unimak Island since 1989, clued Matkin to the large number of killer whales in the area. Traveling commonly as loners or in pods that number only a few, to observe a transient population of 150 killer whales hanging out together, was very exciting.
"There were a lot more there than scientists thought," Laukitis said by phone from Homer. "They are mammal-eating whales, so these guys are there to kill gray whales."
Laukitis said the channel between False Pass and Unimak Island acts as a funnel. In fact, Isanotski Strait in the Aleut language means gap, hole, rent, or tear. The name False Pass was named by early American sailing ship captains who thought their deep-draft ships would not make it through the northern end. Today it is the main passage from the Gulf of Alaska to the Bering Sea.
"Acting as a natural funnel, the gray whales are concentrated in numbers there during their migration and the killer whale population peaks in the area when the grays migrate," Laukitis said. "The peak is in May."
What do killer whales do when they're not eating grays?
"They're munching sea lions," he said. "I can hear the bones crunching."
And it seems they are selective in their taste, Laukitis observes.
"They eat the tongues first," he said.
"No, I think that is a common old tale and not based on more extensive observation, Matkin said. "First, we have watched many times as killer whales have devoured an entire carcass over a period of days. However, the tongue and lips are taken first as they are the most tender and easy to take apart. Often small groups, four to six, maybe a couple more, typically make the kill. They can only eat so many pounds at one time, so they eat the tongue and lips first. The next day they will return to begin eating the remainder.
"However, at times the carcass will end up ashore, although they try to kill them in shallow water so they can come back to the carcass, and it appears that they only eat the tongue and lips.
"The bears have a heyday if the carcass does end up ashore, which happens numerous times during the season."
Laukitis and Matkin served together at one time on the board of the Marine Conservation Council.
Matkin has directed the study for the last four years, which is a NGOS project. Funding is sourced from "all sorts of places," Matkin said, including film companies using the footage for use in nature films, but because negotiations were in progress with some studios he could not divulge their names.