Dwarf sperm whale (Kogia sima)

Species >> Dwarf sperm whale (Kogia sima)

We undertook a survey of the main (windward) Hawaiian Islands during May and June 2003 to examine odontocete population structure.

Small-boat surveys were undertaken in March/April 2006 off the west side of the island of Hawai‘i for the purposes of obtaining dive data from Blainville’s (Mesoplodon densirostris) and Cuvier’s (Ziphius cavirostris) beaked whales, as well as collecting biopsy samples and photo identification of these and other species of odontocetes for studies of stock structure and residency patterns.

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.

Sightings of dwarf (Kogia sima) and pygmy (K. breviceps) sperm whales in Hawaiian waters have only rarely been reported. As part of boat-based surveys of odontocete cetaceans around the main Hawaiian Islands between 2000 and 2003, Kogia were observed on 18 occasions. Kogia were sighted most frequently in deeper portions of the study area (mean depth, 1,425 m) and in calm sea conditions (mean Beaufort sea state, 0.8).

Knowledge of the distribution and relative abundance of odontocete cetaceans is important for helping to understand and potentially mitigate impacts of anthropogenic activities. We present small-boat survey and sighting data from 13 y (2000 through 2012) of field studies around the main Hawaiian Islands. We surveyed 84,758 km of trackline, with effort ranging from 3 to 11 y off each of the four different island areas. We had 2,018 sightings of odontocetes representing all 18 species known to exist in Hawai‘i.