Site Fidelity, Associations and Long-Term Bonds of Short-Finned Pilot Whales off the Island of Hawai'i
Abstract
Short-finned pilot whales (Globicephala macrorhynchus) are the most frequently sighted odontocete in a long-term study in Hawa'i (representing 23.8% of all odontocete sightings from directed research efforts), yet little has been published on this species in Hawaiian waters. Studies elsewhere have suggested that short-finned pilot whales travel in stable mixed-sex groups composed of strongly associated individuals; however temporal analyses of social structure are lacking. To examine site fidelity, association patterns and temporal relationships, I analyzed data from 267 directed research and opportunistic encounters of short-finned pilot whales off the island of Hawai i from 2003 through 2007. Sightings occurred year-round. Analysis of sighting depths in relation to effort indicated short-finned pilot whales are strongly associated with the island slope, with no sightings in water >2,700m deep despite effort to ~5,000m. Using only goodquality photos, I identified 448 distinctive individuals; of these, 305 (68.1%) were seen more than once and 250 (55.8%) were seen in >1 year. Sighting histories varied from 1- 29 sightings per individual (median=3) over the course of the study, suggesting only some individuals exhibit high site fidelity. Degree of residency was assessed using multiyear site fidelity to the study area; individuals seen >/=5 times in >/=3 years were considered core residents (154 individuals), individuals who fell below these criteria but that were seen more than once were termed residents (150 individuals) and those seen on a single occasion were termed visitors (142 individuals). Only 71.9% of the whales were linked by association into a single social network, suggesting the possibility of multiple populations using the study area.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2012
- Accession Number
- ADA570932
Entities
People
- Sabre D. Mahaffy
Organizations
- Portland State University