#Threatenedspecies of the Week: Megaptera novaeangliae (Humpback Whale)

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Photo Credit: Department of Parks and Wildlife Western Australia.

The Humpback Whale is listed as Vulnerable under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) and as Specially Protected Fauna under the Wildlife
Conservation Act 1950.

The main threats to humpback whales are whaling, climate and oceanographic variability and change, overharvesting of prey, noise interference, habitat degradation (including coastal development and port expansion) entanglement (including commercial fisheries or aquaculture equipment, shark safety equipment, marine debris) and vessel disturbance and strike.

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. 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.

mage Credit: Government of Australia, Department of Environment
Image Credit: Government of Australia, Department of Environment

Sexual maturity is reached at four to eight years (average five years). Life expectancy is recorded as at least 48 years but is likely to be significantly longer as shown in other balaenopterids. Rates of natural mortality are unknown but humpback whale calves are particularly vulnerable to predation by the killer whale (Orcinus orca) and may individuals may also die from natural parasitic or disease events/

For the humpback whale, breeding peaks in the winter and the gestation period is 11 to 12 months. Lactation extends over 10 to 12 months although calves have been seen independently feeding at six months of age. The mean calving interval is 2.4 years although it ranges from one year to more than five years.

Humpback whales have a near global distribution and are characterised by high latitude feeding areas and low latitude breeding and calving areas with annual migrations between them. Two populations of humpback whales calve in Australian waters and migrate along the east and west coasts from May to November each year. Humpback whales are also known to migrate past Norfolk Island but it is not known if this is a distinct population, part of the East Australian population, or part of the New Caledonia population. The figure above shows the distribution of humpback whales along the coast of the Australian mainland, including areas of known calving, feeding and resting habitat.

Information Source: Government of Australia, Department of Environment and Department of Parks and Wildlife Western Australia.

 

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