Social Structure of False Killer Whales in Maui Four-Island Region

Project Name:
Social Structure of False Killer Whales (Pseudorca crassidens) in Maui Four-Island Region based on Photo-Identification data

Project Dates:
Ongoing - Phase one: collation of historical catalog

Project Site(s):
Maui Four-Island Region, Hawaiian Islands Humpback Whale National Marine Sanctuary

Project Aims:
To photo-identify as many false killer whales using the Maui Four-Island Region as possible in order to understand group cohesion and stability, age structure, reproductive rates and association patterns.

Project Justification:
There are two subpopulations of False Killer Whales in Hawaiian waters, an insular (or island associated one) and an offshore one. Both subpopulations have been severely depleted over time because of negative interactions with the long-line fishery that caused high mortality rates. The island associated population of false killer whales has been recently listed under the Endangered Species Act. There is relatively little known about the social ecology of these dolphins (although they are called whales they are actually in the same family as other dolphins). Any information that will help increase our knowledge of this population would be useful to help manage this depleted stock. These whales are year-round residents of Hawaii and are true 'locals'.

Project Methodology:
Pacific Whale Foundation researchers are collating an historical catalog of individual false killer whales using photographs collected both during vessel-based research effort by PWF in the past and including donation of photos by the general public. So far we have a catalog of 61 unique individuals from photographs collected between 1998 and 2011. In addition, preliminary information on the distribution of this cetacean in Maui leeward waters is being gleaned from historical data to help the Research Department devise a research protocol to better answer questions about social structure. Systematic line-transect surveys were initiated using our research vessel in 2012. 

Project Permits and/or Collaborators:
In 2012, the PWF research department was granted a permit (NMFS #16479) to conducted photo-identification on this species. 

Management Outcomes:
During sixteen years of observations, there have been 169 reported sightings of false killer whales in the Maui four-island region. Sightings were distributed across the study area including both shallow and deep waters (14 - 219 m). Sightings occurred throughout the year with the greatest number in February, December, and April. The number of sightings in 1998, 2002, 2005, 2010, and 2011 (Jan-May) was especially high as compared to other years.  Behavioral information was collected for all sightings between 2010 and 2011 and gave evidence of foraging behavior for 32% of the sightings.  During the 1999-2000 research effort, 32 false killer whales were individually identified. In 2013,  6 new individuals were added to the catalog. The current PWF false killer whale photo-identification catalog includes 61 individuals.

See Pacific Whale Foundation Publication/Presentation Summary