DOC worked with the University of Auckland to deploy and analyse acoustic devices placed at various points along the coast of Taranaki and Whanganui between November 2016 and April 2019.
DOC’s Manager Marine Species and Threats Ian Angus says the devices, known as C-PODs, detect click trains in the high frequency that Māui and Hector’s dolphins emit when foraging.
“The results give us further evidence that Hector’s or Māui dolphins are regularly present in the coastal waters of Tongaporutu, Taranaki, and visit as far south as Tapuae.
“Despite numerous aerial and boat surveys by DOC and university researchers in this area over several years, visual sightings of Hector’s or Māui dolphins are rare. The most recent verified sighting was off the coast of Patea, just north of the Whanganui River.
“This research confirms that the dolphins are there, even if we don’t always see them,” says Ian Angus. “They are very elusive and not easy to see above water, so acoustic devices under the sea are a valuable alternative way of detecting them.”
The difference in vocalisation allows scientists to reliably distinguish them from other species of dolphin, however, Hector’s and Māui dolphins are the same species and it is not yet possible to distinguish between the subspecies through their vocalisation.
In Taranaki the devices were deployed inside the existing area where protection measures are in place. The next step will be to locate the devices outside this area to verify how far the dolphins range.
Earlier research using the C-PODs shows that Māui and Hector’s dolphins range as far out as 18.2 km (9.8 nm) offshore from Hamilton’s Gap (south heads, Manukau Harbour).
The Minister of Conservation and Minister of Fisheries are currently determining whether further management options are needed as part of the review of the Hector’s and Māui dolphin Threat Management Plan.