Scientists are set to eavesdrop on the critically endangered Maui dolphin, as part of a year-long, Niwa-led project.
Latest estimates put the Maui dolphin population between 57 and 65 so scientists want to find out more about them in an effort to improve their chances of survival.
Maui dolphins are only found on the west coast of the North Island, with the greatest concentration between Manukau Harbour and Port Waikato.
While they are known to congregate close to shore in water less than 20 metres deep, it is uncertain how far offshore they travel and what risks they might face in doing so.
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As part of a collaborative project between the Department of Conservation, the Ministry for Primary Industries and the University of Auckland, Niwa marine ecologists Dr Kim Goetz and Dr Krista Hupman are this month deploying a line of up to nine offshore acoustic moorings stretching from the shoreline to 12m offshore just south of Manukau Harbour.
Each mooring will carry two acoustic devices.
A cetacean and porpoise detector (CPOD) will record detections of the high frequency "clicks" the dolphins produce to hunt prey and navigate.
The second device, a soundtrap, will record a subset of both clicks and whistles.
Goetz said the first step was to establish how far offshore they can be detected.
"Acoustic monitoring provides a reliable way to detect the presence of marine mammals over a long time period," she said.
"In terms of Maui dolphins, we really know very little about their seasonal movements, offshore distribution, and ultimately why they appear to be confined to this area.
"They are an endangered animal so anything we can contribute to increasing our knowledge will be very useful."
A photographic survey of Maui dolphins takes place annually, where distinguishing marks and scars are correlated with known animals.
In addition, mark-recapture biopsy surveys to estimate the number of dolphins is conducted across two years, every five years.
The last one was completed in 2016 so the next one will begin in 2020.
While this provided a valuable snapshot at a given time, Goetz said the acoustic survey would add to this data by providing information collected over an entire year.