New paper on one of Hawai‘i's rarest species of whales, the pygmy killer whale

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.

Summary

The first evidence of a resident population of pygmy killer whales anywhere in the world is provided in a paper published on-line in the journal Marine Mammal Science on December 29, 2008. This is an extremely rare species of whale that has never been studied in detail in the wild and was previously thought to live primarily in the open ocean. Based on photos taken over a 22-year period off the island of Hawai‘i, this study indicates that there is a small resident population off the island. Analyses of associations also indicate that this species forms long-lasting bonds among individuals, similar to the more well-known pilot whales and killer whales. The population is at risk from human impacts because of the small population size. With only very infrequent encounters, monitoring trends in this population in response to potential impacts from naval sonar exercises or fishing activities in Hawai‘i will be almost impossible.

More information on our Hawai‘i odontocete research is available on our Hawai‘i web page

Background and additional details

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. This study was primarily undertaken off the island of Hawai‘i, using photographs taken by researcher Dan McSweeney of the Wild Whale Research Foundation, a non-profit group based on the island of Hawai‘i. These photos were taken over a 22-year period during studies of the more commonly observed short-finned pilot whales. These observations were combined with additional photo-identification effort since 2000 by researchers from Cascadia Research Collective. Additional photos were also provided by Tori Cullins of the Wild Dolphin Foundation, Deron Verbeck, and Beth Goodwin.

This study has shown that although they are encountered only very infrequently, there appears to be 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 were 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.

There are several important conservation and management implications of this work. 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.

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.

The complete citation of the on-line version of the paper is:

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. DOI: 10.1111/j.1748-7692.2008.00267.x

Pdf copies are available from the journal publisher Wiley InterScience or obtained by contacting Robin Baird at rwbaird (at) cascadiaresearch.org

Directed research efforts since 2000 were funded by the Southwest Fisheries Science Center of NOAA Fisheries, the U.S. Navy, and the Wild Whale Research Foundation.

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.

More photos are below.

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.

Pygmy killer whale off Kona. Photo by Dan McSweeney.

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

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

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.

Two pygmy killer whales socializing. Photo by Daniel Webster.

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.

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

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

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