Posted on December 21, 2016
Two new peer-reviewed papers looking at Blainville's beaked whale behavior in relation to U.S. Navy training events in Hawaiian waters were recently published in volume 42 of Aquatic Mammals.
Written by E. Elizabeth Henderson, Stephen W. Martin, Roanne Manzano-Roth, and Brian M. Matsuyama
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
Written by Roanne Manzano-Roth, E. Elizabeth Henderson, Stephen W. Martin, Cameron Martin, and Brian Matsuyama
Abstract: Blainville’s beaked whales (Mesoplodon densirostris) were detected in recorded acoustic data collected before, during, and after February and August U.S. Navy training events in 2011, 2012, and 2013 at the Pacific Missile Range Facility in Kauai, Hawaii. Beaked whale clicks were automatically detected and manually verified to ensure they fit characteristics of foraging echolocation clicks. Verified foraging click detections were spatially and temporally clustered to represent group vocal periods (GVPs) of beaked whale foraging dives. More GVPs were detected before training events than during or after the training events, and GVPs were detected more on hydrophones at the edges and in the southern portion of the range during sonar activity. However, there were also interannual differences in GVP counts across training event phases, indicating that baseline variability in Blainville’s beaked whale GVPs must be distinguished from reduced foraging dive activity during training events with sonar activity to understand the true impact of sonar.
Key Words: Navy activity, mid-frequency active sonar, Blainville’s beaked whales, Mesoplodon densirostris, beaked whale behavior, Hawaii beaked whales, beaked whale group vocal periods
Document Type: Research Article
Page Numbers: 507-518