Rough-toothed dolphin (Steno bredanensis)

Species >> Rough-toothed dolphin (Steno bredanensis)

There are 18 species of odontocetes found around the main Hawaiian Islands, and 11 of these have resident, island-associated populations in the eastern main Hawaiian Islands (Baird 2016). Until recently, relatively little was known about the presence and residency status of most of these species in the western main Hawaiian Islands, in particular around Kaua‘i and Ni‘ihau. The U.S.

A joint project in February 2016 on and around the Pacific Missile Range Facility (PMRF) was carried out utilizing combined boat-based field efforts and passive acoustic monitoring from the Marine Mammal Monitoring on Navy Ranges (M3R) system. Five days of small boat effort were funded by the U.S. Navy and an additional two days of effort were funded by the National Marine Fisheries Service. There were 581 kilometers (36 hours [hr]) of small-vessel survey effort over the course of the seven‑day project.

Rough-toothed dolphins have a worldwide tropical and subtropical distribution, yet little is known about the population structure and social organization of this typically open-ocean species. Although it has been assumed that pelagic dolphins range widely due to the lack of apparent barriers and unpredictable prey distribution, recent evidence suggests rough-toothed dolphins exhibit fidelity to some oceanic islands.

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

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.