New research provides hope for critically endangered Māui dolphin

Date:  23 November 2010

North Island Māui dolphin and South Island Hector’s dolphins were once thought to occupy completely separate stretches of New Zealand’s coastline, but new research has shown that two female Hector’s dolphins have been visiting their North Island relatives.

Researchers hope that the two closely related dolphin sub-species may breed, bringing much-needed genetic diversity to the critically endangered Māui dolphin population.

“We know that Māui dolphin have a limited pool of genetic diversity, so any new input is very welcome,” says Phil Brown, the Department of Conservation’s Māui Dolphin Recovery Group leader.

“Māui dolphin remain classified as a unique sub-species and this recent finding will not change how we manage the small, fragmented population of less than 150 individuals,” he says.

“Māui and Hector’s dolphins have been genetically separate for more than 15,000 years, and even if occasional breeding with Hector’s occurs, it won’t change the makeup of the entire population.”

The two dolphins were identified during the first stage of a Māui dolphin population estimate study carried out by the Department of Conservation, the University of Auckland and Oregon State University in February this year. The study is using DNA profiling to identify individual dolphins.

“At first we didn’t know whether they were Māui dolphin that had retained some Hector’s genes, or whether they were visiting Hector’s straying outside their usual range,” says Mr Brown.

Thanks to genetic analysis that has just been completed by scientists from both universities, it is now possible to confirm that the two dolphins were in fact Hector’s dolphins.

Auckland University’s Dr. Rochelle Constantine presented the findings today at the New Zealand Ecological Society conference in Dunedin.

Future surveys would be necessary to determine if the two female dolphins survived, and if they are able to breed successfully with Māui dolphin.

To understand more about marine mammals in our waters we need more information about them. Mr Brown urges anyone who sees a Māui dolphin to report the sighting by calling the DOC HOTline (0800 362 468).

Background notes

• Māui dolphin is the world’s smallest and rarest dolphin, and is found only on the west coast of the North Island of New Zealand.
• The last population estimate for Māui dolphin, carried out by aerial survey in 2005, showed there was likely to be less than 150 Māui dolphin remaining.
• Twenty-six dolphins were sampled in February this year, and when sampling is repeated this summer, the results will be compared and a new population estimate created.
• A survey was conducted from the current northern range of where Māui dolphin are found to the very south — from New Plymouth to Bayley’s Beach north of the Kaipara Harbour — and samples were collected from north of Raglan to near the Kaipara Harbour mouth.  This encompasses a wider sampling area than has ever been undertaken under previous sampling exercises.
• Hector’s dolphins are found around the coast of the South Island but distribution is patchy. Populations are concentrated between Haast and Farewell Spit in the west, around Banks Peninsula in the east, and Te Waewae Bay and Porpoise Bay/Te Whanaga Aihe in the south.
• Māui dolphin are thought to have been isolated from their more-numerous relatives, South Island Hector's dolphin, for thousands of years. Māui dolphin used to be known as North Island Hector's dolphin, but recent research showed the North and South Island dolphins are separate sub-species that are physically and genetically distinct from each other.

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