Humpbacks invade Northwestern Hawaiian Islands

The Hawaiian humpback whale, whose population seems to be on a steady growth path since whaling for the species was stopped in 1965, appears for the first time to be moving in significant numbers into the Northwestern Hawaiian Islands.

(Photo: NOAA's Ark--Animals Collection)

The whale is one of the few success stories among endangered species. As Hawaiian forest birds like the po'ouli become rare and then go extinct, as Hawaiian monk seals decline in numbers despite significant efforts on their behalf, humpbacks appear to be thriving just by virtue of the fact that we've stopped slaughtering them.

Counts in the late 1970s suggested there were only a few hundred wintering in Hawai'i. Today, numbers are in the neighborhood of 4,000, and some suggestions are that they continue to increase at about 7 percent a year..

They clearly still have problems. They are crashed into and they crash into boats, they are chopped by propellers, they are entangled in buoys lines and fishing gear. But their numbers are on the increase. An active management program under the Hawaiian Islands Humpback Whale National Marine Sanctuary helps.

Until this year, they were believed to be centered on the shallow waters around Maui County, and spreading out to the Big Island and O'ahu and Kaua'i. But scientists never saw many of them in the 1,000 miles of islands, reefs, shoals and atolls to the northwest of Kaua'i and Ni'ihau.

It was assumed anything up there was just passing through.

Now, that's clearly not the case, according to a report in the Sept. 14, 2007, online posting of the Endangered Species Journal, “Identification of humpback whale Megaptera novaeangiliae wintering habitat in the Northwestern Hawaiian Islands using spatial habitat modeling,” by Dave Johnston, Marie Chapla, Lynne Williams and David Mattila.

“This is a significant find. We've seen humpbacks expand their use of the main Hawaiian Islands but were unaware that they also used the Northwestern Hawaiian Islands as wintering habitat,” said Mattila, science coordinator of the Hawaiian Islands Humpback Whale National Marine Sanctuary.

During a March 2007 scientific cruise into the islands, now protected as the Papahānaumokuākea Marine National Monument, the researchers conducted both visual surveys by trained observers scanning the ocean from the ship, and electronic monitoring by listening underwater for whale songs.

They got numerous hits using both techniques.

“The results of our habitat analysis and survey observations document for the first time the existence of extensive wintering habitat used by humpback whales in the (Northwestern Hawaiian Islands),” the authors wrote.

They detected mothers and calves, single whales, groups of whales, and they detected whales in most of the shallow areas through three-quarters of Papahānaumokuākea, from Nihoa all the way to Lisianski.

“It was quite surprising actually. Whenever we surveyed in shallow warm areas, we found humpback whales,” Johnston said.

Whales come down from the cold feeding waters of the arctic in winter, and while in the Hawaiian Islands, they seem to prefer waters less than 600 feet deep, and more than 70 degrees Fahrenheit in temperature. There's a fair amount of that kind of habitat in the main Hawaiian Islands, but there's more to the northwest. Only at the far tip of the archipelago—around Midway and Kure Atoll-- does it appear to be too cold for their winter comfort.

The fact that the whales can use those waters is good news for the whales. Not only is there twice as much habitat for them in those islands, but they're much less likely to run into boats, or have boats run into them—largely because there aren't many boats there.

It's bad news in that there is plenty of marine debris up there, and for most of the year, no one with the capability to disentangle them. Disentanglement teams with specialized equipment are generally available to whales in the main islands.

Papahānaumokuākea is managed by the U.S. Departments of Commerce and Interior, and by the State of Hawai'i. For a copy of the research paper see www.int-res.com/journals/esr. For more about humpbacks, see hawaiihumpbackwhale.noaa.gov/about/humpback.html. For more information about the marine monument see hawaiireef.noaa.gov or www.fws.gov/pacificislands.

© 2007 Jan W. TenBruggencate