While only a single stock of short-finned pilot whales is recognized in Hawai‘i, photo-identification, social network analyses, and genetics have all suggested that there are at least two populations; an open-ocean (pelagic) population and an island-associated (insular) population in which there are western, central and eastern communities. Potential anthropogenic impacts in Hawai‘i may vary depending on both population and community. Off Hawai‘i Island, pilot whales are increasingly the focus of whale watching and swim-with tours and there are high levels of fishing activity, whereas off Kaua‘i they are frequently exposed to naval sonar. Establishing the key habitat and hotspots for different communities within this population could help discern which animals are threatened by each of these factors and inform management decisions to reduce impacts. From 2006-2016, 109 LIMPET satellite tags were deployed on pilot whales, with 86 tagged once and 8 tagged multiple times. Kernel density estimations and minimum convex polygons were used to determine the range of individuals and communities. Core areas for the western (5,243 km2) and eastern (5,945 km2) insular communities were similar, but the central community appears to have a smaller (1,378 km2) core area. The core area of the pelagic population (n=8) was estimated at 34,445 km2, although more information is needed to characterize their range. In addition, 14% of the satellite tag records from the western insular community were within the boundaries of the Pacific Missile Range Facility, highlighting the overlap with their home range off Kaua‘i. Our results show that the three insular communities of short-finned pilot whales utilize different habitats within the archipelago, and though the pelagic animals overlap occasionally, their broad range is primarily in open-ocean waters. Based on these findings, each of the insular communities and the pelagic population are subject to different anthropogenic influences and should be managed accordingly.
Citation:
Walters, E., R. Baird, D. Webster, D. Anderson, S. Mahaffy, G. Schorr, R. Andrews. 2017. Defining key habitats: An analysis of short-finned pilot whale communities in Hawai‘i using satellite tag data. Abstract (Proceedings) 22nd Biennial on the Biology of Marine Mammals, Halifax, Nova Scotia, October 22-27, 2017.