Among the neighbors most of Hawai'i didn't know about is an island community of false killer whales.
After reviewing surveys and photographs dating from 1986 to 2007, a research team was able to conclude that many individuals were being resighted repeatedly over long periods.
(Image: A leaping false killer whale. Credit: Robin W. Baird, Cascadia Research Collective.)
“Individuals were resighted up to 20.1 years after first being documented, showing long-term fidelity to the islands,” said the paper “False killer whales (Pseudorca crassidens) around the main Hawaiian Islands: Long-term site fidelity, inter-island movements and association patterns,” published in the journal Marine Mammal Science.
The crowd of researchers on the paper includes lead author Robin Baird and Gregory Schorr of the Cascadia Research Collective, Antoinette Gorgone and Jay Barlow of NOAA's Southeast Fisheries Science Center, Daniel McSweeney and Daniel Webster of the Big Island's Wild Whale Research Foundation, Dan Salden or the Hawai'i Whale Research Foundation, Mark Deakos of the Maui-based Hawai'i Association for Marine Education and Research, Allan Ligon of the Hawaiian Islands Humpback Whale National Marine Sanctuary, and Sabre Mahaffy of Cascadia and Wild Whale.
The false killer whale is so seldom seen that researchers generally have not focused on the species—largely because getting enough sightings is so cost and time prohibitive. The Baird team kept track of the animals while researching other whales, until it had enough data for a research paper.
As the photos and reports built up, the researchers identified individual whales by scars, deformations and a range of other physical characteristics. They were able to identify about 150 unique individual whales. And more than half of them were seen on more than one occasion—often in more than one year.
“Such evidence implies both that the population of false killer whales around the main Hawaiian Islands is relatively small, and that individuals show considerably fidelity to the islands. Resightings of individuals spanned the entire 21-year duration of our study, indicating that such fidelity is table over periods of many years,” the paper says.
False killer whales seem to readily move up and down the island chain. The same ones seen off O'ahu are also seen off the Big Island. Genetic studies conducted previously suggest the Hawaiian whales are a distinct genetic group from those elsewhere in the tropical Pacific.
“False killer whales around the main Hawaiian Islands clearly form a distinct, island-associated population,” the paper says.
“It appears that false killer whales are another of the growing list of pelagic cetacean species that can form strong associations with island ecosystems,and local populations of these species can essentially become island specialists,” it says.
False killer whales are large, long-lived dolphins, with males capable of growing to nearly 20 feet and females to 15 or so feet in length. (See the National Marine Fisheries Service site on the species at www.nmfs.noaa.gov/pr/species/mammals/cetaceans/falsekillerwhale.htm.)
They feed on deep-ocean fish like mahimahi, tuna and billfish. They sometimes carry food long distances, and share their food with others of their group. Sometimes they are caught in fishing gear.
They are assumed to have strong relationship bonds, since an entire group will strand when one whale is in trouble, and can be reluctant to abandon that individual and return to sea.
For more information, see Cascadia Research's website, www.cascadiaresearch.org.
© 2008 Jan W. TenBruggencate
