Measuring impacts of coastal development on humpback whale resting grounds

October 28, 2014

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A collaborative research project is measuring the possible impacts of coastal development on female humpback whales and their calves as they take rest breaks in sheltered waters along Western Australia’s north-west coast.

Professor Lars Bejder from Murdoch’s Cetacean Research Unit said humpback whales migrate north along the coast of Western Australia in autumn to breed and give birth to their calves in the Kimberley region during winter.  Then the mothers and calves make the long journey back down to Antarctica to feed, going six to seven months with no food.

“Given the lack of food and strenuous journey taken by mothers and calves, it is extremely important that they recharge their batteries by taking rest breaks in our coastal bays as they migrate south,” Professor Bejder said.

“While the humpback whale population off the west coast of Australia is doing well, it is important we protect critical habitats for mothers and calves to ensure a continued healthy population.

“What we’re trying to determine is current resting, suckling and acoustic whale behavior and ambient ocean noise in the resting areas before development activity in these areas begins.

“In turn, we are able to determine any changes in behavior once development starts and recommend strategies to minimise the impact on the whales.”

Professor Bejder said they were keen to share their results and to collaborate with industry and government to provide information for them to meet their environmental, regulatory and statutory responsibilities.

Professor Bejder is conducting the research in collaboration with Murdoch Postdoctoral Fellow Dr Joshua Smith and Adjunct Murdoch researchers Professor Peter Madsen from Aarhus University in Denmark and Associate Professor Dave Johnston from Duke University in the USA.

Professor Madsen said the research project will improve understanding of the ecology and behavior of humpback whales in the Exmouth, Pilbara and Kimberley regions and gain an understanding of how human activities may influence these behavior patterns.

“Humpback resting areas have been slated for development activity such as port construction, oil and gas exploration and shipping,” Professor Madsen said.

“Our research will provide important information on the probability of whale ship strikes, behavioural response of whales to man-made noise, information on calf suckling rates on resting grounds and the behavioural ecology of humpback whales in general.

“In turn this information will aid management agencies such as the Department of Parks and Wildlife and the Federal Government and industry in developing regional conservation strategies to protect humpback whales in areas of rapid coastal development.”

The research team use digital acoustic recording tags (DTAGs) to monitor fine-scale 3D movements, vocal behavior and the acoustic environment of the whales.  The small, light-weight tags attach to the whales for up to 24 hours using suction cups.

The DTAG measures water depth, water temperature and the swimming orientation of the whale at a rate of 800 samples per second.  The tag also records sound up to a frequency of 50 kHz which is made or heard by the whales.

The researchers attach the DTAG using a nine metre hand-held carbon fibre pole.  When the DTAG needs to be removed an automatic release mechanism is employed to electrically corrode the wire assembly which opens a tube and release the suction caps. The detached tag then floats to the surface and is located using a VHF transmitter and antenna.

The research commenced in Exmouth in September 2013 and is ongoing.  Subsequent field efforts will concentrate on humpback whales in areas off the Pilbara coast and the Kimberley and on right whales off the south coast of Australia.

The research is being carried out under permits from the WA Department of Park and Wildlife and a Murdoch University Animal Ethic Permit.  Funding has been supplied from Murdoch University and the National Danish Research Council for Natural Sciences.


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