An unexpected journey: Diurnal movement into deeper waters by humpback whale (Megaptera novaeangliae) mother-calf pairs observed off Northwest Maui, Hawai’i

Pack, Adam; Craig, Alison; Waterman, James

Abstract

Recent studies of humpback whale habitat use in the Hawaiian breeding grounds have revealed that mother-calf pairs favor shallow waters to avoid harassment from male humpbacks. However, human activity in these same shallow waters may, in theory, exert an opposing force on habitat use. During 2005 and 2006, a theodolite was used to obtain position fixes for all pods sighted in the Pailolo, Au’au and Kalohi channels by an observer during five daily 15 minute scan samples at the Kapalua airport overlooking waters off NW Maui. All “fixes” of pods were uploaded to a laptop computer running the custom-made program Cyclops and converted to longitude and latitude coordinates. Depth data were extracted from these coordinates using QGIS. Consistent with other studies of humpback whale habitat use in various breeding grounds, we found that calf pods were in significantly shallower water on average than non-calf pods (median depth calf pods = 56.96 m, IQR = 41.83; median depth non-calf pods = 66.91 m, IQR = 38.69), W(1507) = 136760, N = 1507, p = 0.0009). Unexpectedly, we also found that calf pods tended to occupy progressively deeper water over the course of each day, even when the number of escorts per pod was partialled out (Spearman’s rho rank order correlation rs 5 = 0.24, p

Citation

Pack, A., Craig, A., & Waterman, J. (2017, October). An unexpected journey: Diurnal movement into deeper waters by humpback whale (Megaptera novaeangliae) mother-calf pairs observed off Northwest Maui, Hawai’i. Poster presented at 22nd Biennial Conference on the Biology of Marine Mammals, Halifax, Nova Scotia, Canada

• Presentation Conference Type: Poster
• Conference Name: 22nd Biennial Conference on the Biology of Marine Mammals
• Start Date: Oct 23, 2017
• End Date: Oct 27, 2017
• Deposit Date: Aug 22, 2019
• Public URL: http://researchrepository.napier.ac.uk/Output/1007973