Between a Rock and a Hard Place: Habitat Selection in Female-Calf Humpback Whale (Megaptera novaeangliae) Pairs on the Hawaiian Breeding Grounds

• Main Authors: Cartwright, Rachel, Gillespie, Blake, LaBonte, Kristen, Mangold, Terrence, Venema, Amy, Eden, Kevin, Sullivan, Matthew
• Format: Article in Journal/Newspaper
• Language: English
• Published: eScholarship, University of California 2012
• Subjects: Life Sciences; GIS; humpback whale; Megaptera novaeangliae; cetaceans; marine ecology; habitat; Au'au channel; Boat Harbor; Pacific; Humpback Whale
• Online Access: http://www.escholarship.org/uc/item/8d15b7r2

The Au’au Channel between the islands of Maui and Lanai, Hawaii comprises critical breeding habitat for humpback whales(Megaptera novaeangliae) of the Central North Pacific stock. However, like many regions where marine mega-fauna gather,these waters are also the focus of a flourishing local eco-tourism and whale watching industry. Our aim was to establishcurrent trends in habitat preference in female-calf humpback whale pairs within this region, focusing specifically on thebusy, eastern portions of the channel. We used an equally-spaced zigzag transect survey design, compiled our results in aGIS model to identify spatial trends and calculated Neu’s Indices to quantify levels of habitat use. Our study revealed thatwhile mysticete female-calf pairs on breeding grounds typically favor shallow, inshore waters, female-calf pairs in the Au’auChannel avoided shallow waters (,20 m) and regions within 2 km of the shoreline. Preferred regions for female-calf pairscomprised water depths between 40–60 m, regions of rugged bottom topography and regions that lay between 4 and6 km from a small boat harbor (Lahaina Harbor) that fell within the study area. In contrast to other humpback whalebreeding grounds, there was only minimal evidence of typical patterns of stratification or segregation according to groupcomposition. A review of habitat use by maternal females across Hawaiian waters indicates that maternal habitat choicevaries between localities within the Hawaiian Islands, suggesting that maternal females alter their use of habitat accordingto locally varying pressures. This ability to respond to varying environments may be the key that allows wildlife species topersist in regions where human activity and critical habitat overlap.