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Occurrence and Habitat Use of Foraging Blainville’s Beaked Whales (Mesoplodon densirostris) on a U.S. Navy Range in Hawaii
Abstract: Blainville’s beaked whales (Mesoplodon densirostris) were detected through passive acoustic monitoring recordings of the hydrophones at the Pacific Missile Range Facility (PMRF) off Kauai, Hawaii, from 2011 through 2013. Group vocal period (GVP) detections were analyzed for temporal (intra- and inter-annual and diel) and spatial (depth, slope, and range extent) patterns. A habitat model was developed using those parameters as predictor variables in Blainville’s beaked whale foraging dive distributions. No monthly or annual trends in GVP rates were found, but there was some diel periodicity found in GVP rates related to the lunar cycle. In addition, a strong relationship was found between bathymetric features and GVP rates, with most dives occurring over steep slopes and depths between 2,000 and 3,000 m. While GVPs occurred across the range throughout each year, they were concentrated in those areas of preferred habitat. GVP rates were also compared against Navy training activity to assess whether foraging behavior was affected by active sonar or explosive sounds. Similar to other Navy ranges, biannual multi-day training events did decrease GVP rates, but all of the other training activity did not appear to affect GVP rates over sampling periods of a week to a month. These results are the first description of baseline foraging behavior for Blainville’s beaked whales at PMRF and provide some insight into the habitat use patterns related to both the natural environment and anthropo¬genic impacts.
Key Words: Hawaii, foraging dives, habitat use, echolocation clicks, Blainville’s beaked whale, Mesoplodon densirostris
Document Type: Research Article
Page Numbers: 549-562