pygmy killer whale (Feresa attenuata)

Of the 18 species of odontocetes known to be present in Hawaiian waters, small resident populations of 11 species—dwarf sperm whales, Blainville’s beaked whales, Cuvier’s beaked whales, pygmy killer whales, short-finned pilot whales, melon-headed whales, false killer whales, pantropical spotted dolphins, spinner dolphins, rough-toothed dolphins, and common bottlenose dolphins—have been identified, based on two or more lines of evidence, including results from small-boat sightings and survey effort, photo-identification, genetic analyses, and satellite tagging.

Most of what we know about cetacean biology and ecology comes from studies of relatively common species. Despite their distribution throughout the tropics and sub-tropics, pygmy killer whales (Feresa attenuata) are rare throughout their range and are one of the most poorly-known species of odontocetes. During a 22-yr study of short-finned pilot whales (Globicephala macrorhynchus) off the island of Hawai‘i, we opportunistically photo-identified pygmy killer whales whenever encountered.

Pygmy killer whales (Feresa attenuata) are a rare tropical oceanic odontocete that are normally found close to shore only around oceanic islands (Donahue and Perryman 2009, McSweeney et al. 2009). In the Exclusive Economic Zone (EEZ) surrounding the Hawaiian Islands there is a single stock of pygmy killer whales recognized (Carretta et al. 2010). In the Hawaiian EEZ they are the third-least abundant of the 12 species of delphinids documented, with an estimated abundance of 956 individuals (CV = 0.83; Barlow 2006).

Pygmy killer whales (Feresa attenuata) have historically been a poorly studied species. They are typically found in the open ocean as well as around oceanic islands. However, they are naturally rare, cryptic, and often elusive, making them difficult to sample. Photo-identification and satellite telemetry data suggest the existence of an island-associated population around the main Hawaiian Islands. There are also reports that they are highly vulnerable to artisanal fisheries bycatch in some areas.

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