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Gray Whales' Trip Home Is a Killer

May 09, 1997|PETE THOMAS

If you're among those who spent at least one day whale watching this season, chances are you had close encounter or two and went home feeling pretty good about the plight of the California gray whale.

No longer are people allowed to fire harpoons into their massive bodies--or to harass them in any way. Because of this, as you might have learned, the grays have built their population back to near-historic levels. There are about 24,000 of them.

You might even think the grays pretty much have it made, spending their winters frolicking in Baja California's balmy lagoons, pumping out little whales and bringing them home to live high in the nutrient-rich waters off Alaska.

Think again.

That 6,000-mile journey home, especially for mother and calf, can be a killer.

That has become strikingly evident in recent weeks in the murky depths of a submarine canyon in the Monterey Bay National Marine Sanctuary. That's where another beloved water-dwelling mammal, the killer whale, has been waiting in ambush.

Killer whales are masters of surprise. It is believed they can hear the grays coming.

A hunting party of 15-30 killer whales, usually part of a larger pod, generally strikes fast and hard, grabbing the mother gray by her fins, chasing and harassing her until she becomes separated from her calf. They then haul down and drown the calf, then feast for hours.

The mother, despite her 30 tons, has no teeth and only a powerful fluke with which to fight the smaller, much quicker killer whales. She is, in essence, helpless to save her calf and usually resumes her northbound journey alone.

This seasonal phenomenon is truly one of nature's most dramatic spectacles, one rarely witnessed by the weekend whale watcher, who probably has no idea that "orcas," portrayed in recent movies as such amiable creatures, can be so violent.

"Most people don't even know we have killer whales off our coast," said Nancy Black, a Monterey marine biologist who has studied killer whales for eight years. "This is not unusual. It's only unusual that we've had so many [reported attacks] in so short a period of time."

With assistance from the sanctuary, which occasionally offers the use of a boat and crew, Black has been busy following up on those reports.

On April 11, she was on a sanctuary boat and watched as 25-30 killer whales dined on a calf that had been killed before she got there.

"They were stripping off blubber and feeding on the blubber and tongue," she said. "That's what they usually get first."

On April 13, a crew aboard a fishing boat reported 15 killer whales chasing grays south of Monterey.

On April 21, aboard the Point Sur Clipper with researcher Richard Ternullo, Black spent several hours observing and photographing 15 killer whales reducing what had been a 20-foot juvenile gray whale to practically nothing.

"Half the whale was gone and they were feeding on the last half, ripping off pieces of blubber," she said. "It was pretty dramatic. They reminded me of sharks, twisting and shaking as they tried to grab the pieces. We watched for four hours, and obviously before that, other whales had been feeding on the [gray]. Then after four hours, they grouped together and left all at once, traveling to the northwest."

On April 24, Black went out and again saw killer whales feeding on another gray whale carcass. But 30-knot winds forced the boat to turn back.

"Since then, we've had a few other reports, the last one on Monday," she said. "A person from [nearby] Aptos saw grays coming toward the beach and killer whales chasing them."

Not all killer whales live up to their name in such fashion.

There are two classifications for killer whale pods, resident and transient. Resident pods are relatively small groups that rarely venture far from their home regions. They feed largely on fish and squid. Transient pods pass through specific areas from time to time and tend to prey on other mammals.

It is the transients, obviously, that are making life rough for mother grays and their calves as they migrate home. The male gray, a promiscuous fellow, does not accompany the cow and calf.

Transient killer whales are sophisticated hunters. One probable reason they choose to stake out the Monterey area is because of the deep canyon the grays must pass through en route home.

Mother grays generally stay fairly close to shore on their return trip, where perhaps they rely on kelp beds and a noisier inshore sea to help them travel undetected.

"But when they cross that canyon and get toward the other side, they approach a shelf and that is where the killer whales get them," Black said. "The killer whales may find the grays by listening for them. The grays make a low-frequency knocking sound and seem to make more sound when they're coming up to the shallows, perhaps for navigation purposes."

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