The humpback whale is a moderately large baleen whale. The maximum recorded length is 17.4 m, and females are generally 1.0–1.5 m longer than males. Southern Hemisphere humpback whales generally have a greater degree of white colouration on their ventral surface compared to darker Northern Hemisphere whales but there is no genetic evidence to support the need for subspecies status. The humpback whale has distinctive markings on the ventral side and trailing edge of their flukes as well as on their dorsal fins and flanks that are used for individual identification. Their dorsal fin is distinctive from other balaenopterid whales as they have a hump on the leading edge of their dorsal fin. The humpback whale produces a variety of sounds throughout their habitat range. These sounds can be used for foraging, when in distress and in non-mating, social circumstances. The most studied vocalisations are songs produced by solitary males. The song frequency ranges from less than 20 Hz to 8 kHz. A whale can sing for a period of minutes to hours and the song can vary over a range of frequencies with more powerful parts of the song audible over several kilometres underwater. The exact function of male humpback whale song has yet to be determined but it is believed to be an integral part of male behaviour as a form of sexual display. Feeding ground song has only recently been recorded from a Southern Ocean Antarctic feeding area, where song transmission has been hypothesised as a form of cultural transmission between the neighbouring South Pacific populations.
Humpback Whale |
Government evidence of impact of climate change:
Australian Government Department of Agriculture, Water and the Environment, Species Profile and Threats Database, Megaptera novaeangliae
Climate and Oceanographic Variability and Change Potential impacts of climate change include increasing sea surface temperatures; decreasing sea ice cover; rising sea levels; changes to ocean circulations; ocean acidification and changes in salinity (Learmonth et al. 2006).
Climate change may lead to changes in species abundance; migration timing and range; species distribution; changes to prey predator relationships; prey availability and reproductive timing and success; which could impact on the health and survival of species (IWC 2006).
The abundance of krill is affected by many key factors including fisheries; predator prey nutrient cycling; and climate change.
Ocean acidification is of concern for marine species with the increased levels of atmospheric carbon dioxide leading to increased absorption of carbon dioxide into the ocean and a subsequent decrease in the pH of sea water (Levitus et al. 2000).