Pygmy killer whales in Hawai‘i

Pygmy killer whales (Feresa attenuata) off Kona. Photo by Deron Verbeck. All three individuals in the photo have been documented numerous times, almost always together: in the foreground, HIFa012 in our catalog, an adult male, has been documented 20 times since 1996; in the middle, HIFa002, also an adult male, has been documented 23 times since 1994; in the back (far left), HIFa003, an adult female, has been documented 26 times since 1991.

Two pygmy killer whales socializing. Photo by Daniel Webster.

The pygmy killer whale, a small toothed whale found in tropical oceanic waters world-wide, is one of the least-frequently encountered species of delphinids (oceanic dolphins) in the world. More is known about pygmy killer whales in Hawai‘i than anywhere else in the world, based primarily on a long-term photo-identification study undertaken by researcher Dan McSweeney of the Wild Whale Research Foundation, a non-profit group based on the island of Hawai‘i. Dan's observations have been combined with additional photo-identification effort since 2000 by researchers from Cascadia Research Collective, and results published in Marine Mammal Science in 2009. Additional photos were also provided by Tori Cullins of the Wild Dolphin Foundation, Deron Verbeck, and Beth Goodwin.

Pygmy killer whales are closely related to false killer whales, short-finned pilot whales and melon-headed whales, all of which are found in Hawaiian waters. The are most frequently confused with melon-headed whales.

Download the above for information on how to distinguish between pygmy killer whales and melon-headed whales.

Pygmy killer whale with healing injury on mouth-line, probably due to an interaction with a line fishery. Photo by Russ Andrews.

Although they are encountered only very infrequently, there is a small resident population of pygmy killer whales off the island of Hawai‘i. This is the first evidence of a resident population of this species anywhere in the world. Individuals have been resighted over periods of up to 21 years, and there is evidence they use the area year-round. In addition, using photographs of individuals traveling together in the same group, it is clear that some associations among individuals are very stable, similar to the long-term associations seen in some other species of whales such as killer whales and short-finned pilot whales.

Pygmy killer whale rolling at the surface, December 2008. Photo by Robin Baird. Note the scarring on the mouth-line, probably due to interaction with a line fishery.

Because of the small population size the population is more at risk from human impacts than most species of whales and dolphins in Hawaiian waters. A stranded pygmy killer whale found dead on O‘ahu in 2006 had evidence of interacting with fishing gear (a hook and line injury in the mouth), and Hawai‘i is also home to regular naval sonar exercises that potentially could impact this species. With the very low encounter rates it will be almost impossible to determine whether the population is increasing or decreasing or monitor the impacts of such activities as naval exercises. Also, the standard methods NMFS uses for monitoring population trends, large-vessel line-transect surveys, will not be feasible, given the low encounter rates.

Pygmy killer whale off Kona. Photo by Dan McSweeney.

Two pygmy killer whales off Kona, December 2008. Photo by Robin Baird.

Pygmy killer whales resting underwater off Kona. Photo by Deron Verbeck. The individual in the foreground, HIFa006, is an adult female seen 18 times since 1994, the most recent on December 7, 2008.

A pygmy killer whale calf with shark bite wounds. Photo by Dan McSweeney.

Another view of the pygmy killer whale calf with shark bite wounds. Photo by Robin Baird.

Pygmy killer whales prior to deployment of a suction-cup attached time-depth recorder/VHF radio tag, used to study diving behavior. Photo by Robin Baird.

Pygmy killer whales. Photo by Jay Barlow.

Cascadia Research and the Wild Whale Research Foundation are continuing studies of this species in Hawai‘i. In early December 2008 the first-ever satellite tag was deployed on a pygmy killer whale off the island of Hawai‘i to examine movements, and another satellite tag was deployed on a pygmy killer whale in April 2009..

Satellite tagged pygmy killer whale with companions (including HIFa006, photo above), December 7, 2008. Photo by Robin Baird.

For more information:

McSweeney, D.J., R.W. Baird, S.D. Mahaffy, D.L. Webster, and G.S. Schorr. 2008. Site fidelity and association patterns of a rare species: pygmy killer whales (Feresa attenuata) in the main Hawaiian Islands. Marine Mammal Science 25:557-572. Download PDF copy

All photos are copyrighted and should not be used without permission.

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