Cuvier’s beaked whales make exceptionally long and deep dives to forage on bathypelagic prey. The species is of conservation concern because of strandings which have occurred in association with Navy training exercises employing tactical sonar. We used depth-transmitting satellite tags to study the diving behavior of this species near Cape Hatteras, North Carolina and to generate baseline data for a planned behavioral response study in this area. We deployed LIMPET tags on nine adult whales from 2014-2016 and obtained 3,266 hours of data. Tag durations ranged from 2-60 days (median=34 days). One tag recorded a dive to 3,567 meters, the deepest dive of any air-breathing vertebrate, although this observation should be interpreted cautiously because it is beyond the calibration range of the tag’s pressure sensor. We observed characteristic diving patterns of the species, with deep foraging dives interspersed with series of shallow dives. Deep dives (>800 meters, n=1,295) had an animal-weighted mean depth of 1,433 meters and duration of 58 minutes, and occurred at 0.41 dives/hour. Shallow dives ( < 8 00 meters, n=4,140) averaged 281 meters and 19 minutes. Dives at night were significantly shorter duration for both dive types. Surface durations averaged only 2.2 minutes, typical for this species. Final surface intervals prior to deep dives were significantly longer (4.7 minutes) than those following deep dives (2.3 minutes) or between shallow dives (1.9 minutes). The surface times are very short given the long duration of these dives, but the longer surface intervals preceding deep dives indicate that they prepare for their dives prior to submergence. Future work will link these dives with local bathymetry to both test the hypothesis that these whales are foraging at or near the sea floor, and to potentially predict the timing of deep dives using prior dive and surface times.
Citation:
Shearer, J., R. Baird, D. Webster, H. Foley, Z. Swaim, J. Bell, A. Read. 2017. Diving behavior of Cuvier’s beaked whales (Ziphius cavirostris) off Cape Hatteras, North Carolina. Abstract (Proceedings) 22nd Biennial on the Biology of Marine Mammals, Halifax, Nova Scotia, October 22-27, 2017.