Social Structure of False Killer Whales in Maui County Waters

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

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

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

Project Aims:
To photo-identify as many false killer whales using the Maui County Four-Island Area 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 is being considered for listing 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:
At this point in time, 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 68 unique individuals from photographs collected between 1995 and 2011. In addition, preliminary information on the distribution of this cetacean in Maui County 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 have been initiated using our research vessel in 2012.

Project Permits and/or Collaborators:
This project relies on data collected under past and current (LOC#13427-05) NOAA/NMFS Permitted research.

Data are also collected during regular PWF eco-tour operations. For the current opportunistic phase of this research, no permit is required given that the cetaceans are not actively approached or ‘taken’ by our vessels. This project is conducted by Pacific Whale Foundation's naturalists in collaboration with the Research Department.

Management Outcomes:
During sixteen years of observations, there have been 169 reported sightings of false killer whales in Maui County waters. Sightings were distributed across the study area including both shallow and deep waters (14-219 m). However, the majority of encounters occurred at depths between 50 and 75 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, 54 false killer whales were individually identified. In 2011, observers photographed and identified false killer whales, and added 14 new whales to the catalog. The current PWF false killer whale photo-identification catalog includes 68 individuals.

See Pacific Whale Foundation Publication/Presentation Summary