An examination of sub-surface and night-time behaviour of humpback whales in Hawaiian waters

Research on the diving behaviour of humpback whales in Hawaii has been undertaken since 2000. In 2000 this work was supported by the Hawaiian Island Humpback Whale National Marine Sanctuary, the Island Marine Institute, Lahaina, Maui, and the Hawaii Wildlife Fund. During 2001 this work was supported by the Island Marine Institute and a donation by Tom and Chris Brayton.

A report on this work (from 2000) is available as an Adobe PDF file:

Baird, R.W., A.D. Ligon and S.K. Hooker. 2000. Sub-surface and night-time behavior of humpback whales off Maui, Hawaii: a preliminary report. Report prepared under Contract #40ABNC050729 from the Hawaiian Islands Humpback Whale National Marine Sanctuary, Kihei, HI, to the Hawaii Wildlife Fund, Paia, HI.

Aspects of this work were presented at the 14th Biennial Conference on the Biology of Marine Mammals, Vancouver, Canada, in December 2001.

The following is a description of the research and its relevance to Sanctuary management goals.

Overview of the research

Humpback whales, like other cetaceans, spend the majority of their time beneath the water’s surface, yet relatively little is known of their activities there. Studies of diving (sub-surface) behaviour of humpbacks have been limited to near-surface visual and video observations made by divers or snorkelers (or through clear-walled chambers) on the breeding grounds (e.g., Baker and Herman 1984), to sonar-based studies on feeding grounds (Dolphin 1987), and to one short-term (3 hour) deployment of a tag which recorded dive depth (and transmitted this information via a VHF signal) of a whale in a migratory area (Hamilton et al. 1997). Underwater visual or video observations in the clear waters of the Hawaiian breeding grounds can provide valuable information on under-water behaviour, but are biased towards slow-moving individuals near the surface. One humpback whale has been recorded diving to 240 m (Hamilton et al. 1997), thus humpback whales certainly have the potential to spend a substantial proportion of their time out of sight of near-surface observers. Sonar systems can be used to track whales underwater, though there are a variety of limitations of such operations which constrain the quantity and quality of data which can be collected (Hooker and Baird 2000). The only way of obtaining continuous and detailed dive data is through the attachment of tags which record depth. Such tags have been used with a number of species of cetaceans (e.g., Baird 1998; Hooker and Baird 1999, 2000).

The primary goal of this research project is to obtain a better understanding of the sub-surface and night-time behaviour of humpback whales in the Hawaiian Islands. Data are being collected using remotely-deployed suction-cup attached time-depth recorder (TDR)/VHF radio tags. These tags are recoverable, and so high-resolution information can be collected by the TDRs (e.g., depth and velocity can be collected once per second, and light and water temperature levels every 5 seconds) and downloaded to computer upon recovery. A number of specific questions will be addressed with these data. These include: 1) what proportion of time do animals spend visible at the surface? (for calculation of correction factors, to allow for calibrating aerial or ship-based surveys); 2) do diurnal patterns of behaviour exist?; 3) what types of sub-surface reactions do animals have to vessel approaches and how do these differ from natural causes of harassment?; 4) where do animals spend their time in the water-column, particularly in relation to exposure to depth-specific threats?; and 5) can behaviours observed at the surface be used to describe underwater activities?

During the spring of 2000, we used suction-cup attached time-depth recorder/VHF tags with humpback whales off the south-west side of Maui. These are the same tags which have been deployed on pantropical spotted dolphins and false killer whales in Hawaiian waters since 1999 (Baird et al. 2001). Once a tag has been deployed, a focal follow of the tagged animal is undertaken, typically at a distance of 20-200 m. Continuous information is recorded on group size, composition, distance between individuals (and relative orientation), directionality of travel, location (determined using a GPS), interactions with other species, and the occurrence of specific behavioural events (e.g., breaches, spyhops, tail-lobs). Acoustic sampling is undertaken to monitor vocal activity of the tagged animal or group.

Suction-cup attached VHF radio tags (not including time-depth recorders) have been previously used with humpback whales (Goodyear 1989), with an average attachment duration of about 15 hours (n=12). Under NMFS Permit No. 731-1509, up to 15 humpbacks could tagged in 2000. By the end of the season, 15 humpbacks were tagged, and 14 of the 15 tags were recovered. Reactions to tag deployment have been minimal or not even noticeable. Tags remained attached for periods ranging from 8 minutes to 17 hours (average of about 5 hours). Most of the tags were deployed on whales in competitive groups, and two were slightly damaged from impacts during these competitive interactions, but data from all tags (except for one where the TDR battery failed) were successfully recovered. During 2001 an additional 17 tags were deployed on humpbacks.

Relevance of research to Sanctuary management goals

All four of the Working Groups at the “Workshop to Assess Research and Other Needs and Opportunities Related to Humpback Whale Management in the Hawaiian Islands” (Payne et al. 1997) identified research needs which are being addressed by the tagging project.

Literature cited

Baird, R.W. 1998. Studying diving behavior of whales and dolphins using suction-cup attached tags. Whalewatcher 32(1):3-7.

Baird, R.W., A.D. Ligon, S.K. Hooker, and A.M. Gorgone. 2001. Sub-surface and night-time behaviour of pantropical spotted dolphins in Hawaii. Canadian Journal of Zoology 79:988-996

Baker, C.S., and L.M. Herman. 1984. Aggressive behavior between humpback whales (Megaptera novaeangliae) wintering in Hawaiian waters. Canadian Journal of Zoology 62:1922-1937.

Dolphin, W.F. 1987. Dive behaviors and estimated energy expenditures of foraging humpback whales in southeastern Alaska. Canadian Journal of Zoology 65:354-362.

Goodyear, J.D. 1989. Night behavior and ecology of humpback whales (Megaptera novaeangliae) in the western North Atlantic. M.Sc. Thesis, San Jose State University.

Hamilton, P.K., G.S. Stone and S.M. Martin. 1997. Note on a deep humpback whale Megaptera novaeangliae dive near Bermuda. Bulletin of Marine Science 61:491-494.

Hooker, S.K., and R.W. Baird. 1999. Deep-diving behaviour of the northern bottlenose whale, Hyperoodon ampullatus (Cetacea: Ziiphidae). Proceedings of the Royal Society of London B. 266:671-676.

Hooker, S.K., and R.W. Baird. 2000. Diving and ranging behaviour of odontocetes: a methodological review and critique. Mammal Review 30: in press.

Laake, J.L., J. Calambokidis, S.D. Osmek and D.J. Rugh. 1997. Probability of detecting harbor porpoise from aerial surveys: estimating g(0). Journal of Wildlife Management 61:63-75.

Payne, C.M., B. Phillips and E. Nitta. Editors. 1997. Report of the workshop to assess research and other needs and opportunities related to humpback whale management in the Hawaiian Islands. NOAA Technical Memorandum NMFS-OPR-11.

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