Tagging feasibility and diving of Cuvier's beaked whales (Ziphiuscavirostris) and Blainville's beaked whales (Mesoplodon densirostris) in Hawai'i
Baird, R.W., D.J. McSweeney, A.D. Ligon and D.L. Webster. 2004. Tagging feasibility and diving of Cuvier's beaked whales (Ziphiuscavirostris) and Blainville's beaked whales (Mesoplodon densirostris) in Hawai'i. Report prepared under Order No. AB133F-03-SE-0986 to the Southwest Fisheries Science Center, National Marine Fisheries Service, La Jolla.
Detailed information on diving (sub-surface) behavior of beaked whales (family Ziphiidae) is only available for one of the 21 recognized species. Information on diving behavior of additional species within the family Ziphiidae is needed to evaluate their susceptibility to impacts from anthropogenic sound (such as high-intensity sonars) and to develop correction factors for survey-based estimates of abundance or density. In 2002 and 2003 we attempted to collect dive data on two species of beaked whales, Cuvier’s (Ziphius cavirostris) and Blainville’s (Mesoplodon densirostris), in Hawai‘i, using remotely-deployed suction-cup attached time-depth recorder/VHF radio tags. We covered 4,144 km of trackline during 327 hours of search effort, and encountered three groups of M. densirostris (group size range 1-9, mean = 3.7) and eight groups of Z. cavirostris (group size range 1-5, mean = 2.9). Seven tagging attempts were made, and two tags attached, one to a Z. cavirostris (attachment duration minimum 7 h) and one to a M. densirostris (attachment duration 2.09 h). These are the first tags that have been deployed on either species. The Z. cavirostris tag was not recovered, but a combination of VHF signals and visual observations resulted in recording of 12 long-duration dives (duration range 19-87 min, mean = 31.5). The tagged M. densirostris remained in a social group for at least 1.88 hours after tagging. Dives during this social period averaged 7.47 min in duration (SD=2.49), to an average depth of 58.6 m (SD=35.5), and the whale spent ~26% of its time in the top 10 m of the water column. One dive to 890 m, with an estimated duration of at least 23.3 min, was likely for foraging. Given the bottom depth in the area, this dive was likely to, or close to, the bottom. This study has demonstrated that tagging of these species is feasible, and that M. densirostris may dive deeply for foraging.