Migration schedule is not well understood

By Chris Oliver
Advertiser Staff Writer

Arriving from the deep blue, their 3,000-mile journey done, humpback whales cruise around the Islands like any good tourists. But how do they find their way here from Alaska or decide when it's time to start their journey ... and go back?

"These are tough questions to answer in whales because we can't do the same kinds of experiments as we do in other animals," said Dwayne Meadows, director of research at the Pacific Whale Foundation on Maui. "How they navigate is not certain, but many other animals use a combination of magnetic and other cues such as sunlight features and time and this may be likely for whales, too."

Meadows says migration does seem to relate to weather and food levels in the North Pacific. "Whales certainly know that when it starts to get icy, that becomes a problem, even if their biological clock would normally keep them around."

Meadows said Hawai'i's warm water is helpful to the whales for several reasons: "Calves have little blubber, so in warm water, they can survive easier and there may be less predators here where there is less food to establish large populations of the kind that would eat whales, for example, big sharks or large-toothed whales."

From Hawai'i's breeding grounds, the whales disperse each spring to feeding areas across the North Pacific, swimming at 3 to 4 mph. In March and April 1995, Bruce Mate of Oregon State University tagged six whales with satellite-monitored radio transmitters as they passed the Na Pali coast on Kaua'i. He monitored interisland travel and recorded their departure for Alaska for periods ranging from half a day to 17 days.

Of the six whales, one adult traveled 150 miles to O'ahu, another visited Penguin Bank and five islands in 10 days, three whales traveled independent parallel courses north-northeast toward the Gulf of Alaska, and a female with her calf, the fastest of the lot, traveled 500 miles in 4 1/2 days.

"The tracking suggested faster interisland movements than had been previously thought," Mate said. "Two whales traveled at an average speed of 90 miles a day; at that speed, migration to the upper Gulf of Alaska could be accomplished in 39 days. If the fastest whale's speed was maintained on a straight course, the entire migration could be accomplished in as little as 28 days."