Rough-toothed dolphins on a Navy range in Hawai'i: using LIMPET satellite-tag data to assess movements, habitat use, and overlap with Navy activities

Publications >> Rough-toothed dolphins on a Navy range in Hawai'i: using LIMPET satellite-tag data to assess movements, habitat use, and overlap with Navy activities

Citation

Webster, Daniel L., R. W. Baird, B. K. Rone, D. B. Anderson. 2015. Rough-toothed dolphins on a Navy range in Hawai'i: using LIMPET satellite-tag data to assess movements, habitat use, and overlap with Navy activities. Abstract (Proceedings) 21st Biennial Conference on the Biology of Marine Mammals, San Francisco, California, December 14-18, 2015.

Abstract

Much of the U.S. Navy's training activities in Hawai'i occur on the Pacific Missile Range Facility (PMRF), an area between the islands of Kaua'i and Ni'ihau. Surveys show that rough-toothed dolphins are the most frequently encountered and likely most abundant odontocete found on PMRF. Long-term photo-identification data indicate that individuals show considerable fidelity to Kaua'i and Ni'ihau, and genetic studies indicate they are demographically isolated from rough-toothed dolphins off Hawai'i Island. We use LIMPET satellite tag data from 14 individuals tagged between 2011 and 2015 to assess site fidelity and movements of rough-toothed dolphins around Kaua'i and Ni'ihau, and estimate the overlap of the population with PMRF. Tag data were obtained for periods from 3.4 to 21.8 days (median=12.5). Assessment of overlap of movements indicate that two individuals were not acting independently, thus analyses were restricted to 13 individuals. Although tagged dolphins moved a cumulative distance of 11,994 km, grand median distance from tagging locations was only 25.5 km (median of maximums=57.6 km). Individuals remained broadly associated with Kaua'i and Ni'ihau with one moving to western O'ahu and back. Grand median depths and distance from shore for tagged animal locations were 1,215 m and 12.2 km, respectively. Only 6 of 13 individuals were tagged on PMRF, but all individuals used the range, moved onto PMRF a mean of once every 30 hours and spent a mean of 38.9% of their time on PMRF. Home range and core area calculated using the 95% and 50% kernel density utilization distributions of tag data were 11,953 and 1,413 square km, respectively, with 48% of the dolphin's core area overlapping with PMRF. Given the frequency of Navy training activities on PMRF, results indicate that rough-toothed dolphins are likely regularly and repeatedly exposed to mid-frequency active sonar and other Navy activities on PMRF.

Associated projects