Migratory mysticetes, such as the humpback whale, are well known for their extensive annual migrations. From their cool, productive feeding grounds, they travel annually over long distances to favored tropical breeding regions. Hawaii’s humpback whales are no exception; these whales travel from all over the North Pacific and congregate in the warm waters around Maui each year. For mothers, the benefits of raising their calves in these warm, tropical waters justify a trip of over 3000 miles each way. Essentially, these migrations may be an anti-predator strategy, as they place the young calves beyond the typical range of their main predator, the transient orca. In the relative safety of their nursery, naïve young, calves develop anti-predator behaviors such as twirling, breaching and the ability to extend breath holding. These new skills will improve the young calves’ chances when orca attack. Additionally, nursery waters provide a region where both the mother and her calf can conserve their energy. Nearly all breeding areas occur in relatively warm waters, where SST > than 21°C and within breeding regions, shallow, inshore waters may be especially important to female-calf pairs. Several studies show that females with calves preferentially use inshore waters, thereby avoiding areas where active breeding groups congregate. This avoidance may be warranted, as associations with multiple male groups lead to increased energy expenditure for female-calf pairs. Inshore waters are often calmer too, and this may be an important consideration as many young mysticete calves are relatively poor swimmers. Within Hawaiian waters, the AuAu channel, between Maui and Lanai is especially favored by mother and calf pairs and so comprise critical nursery habitat for this endangered species. However these waters are busy, with a flourishing whale watching industry running out of Lahaina Harbor, cruise ships frequently mooring in the area and also extensive land based agricultural runoff potentially impacting the waters of the channel. In 2008, the Keiki Kohola Project launched a new project, to see how mother and calf pairs fare in the waters of the AuAu Channel. Our aim is determine which regions of the channel are favored by mother and calf pairs and to see how variations in the abiotic conditions across the channel may influence their habitat preference. In this study, the students of California State University Channel Islands have joined with the volunteers of the Keiki Kohola project. The study is now entering it’s third season and results to date suggest that while the channel is still popular with mother and calf pairs, they may not be choosing the areas that we would expect.
Follow the link below to see our progress to date Habitat choice in Hawaii’s humpback whales.
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| CSUCI Inaugural Marine Mammal Studies Group ( Spring 09) |
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