A survey of one of the world’s rarest dolphins is underway off the west coast of the North Island.

Māui dolphins are only found between Auckland and Taranaki and particularly from the Manukau Harbour to Port Waikato.

The last survey in 2016 indicated there were only 63 of the critically endangered mammals aged over one year.

Department of Conservation marine species manager Ian Angus said the survey was important in the survival of the species.

He said it provided information on the number of males and females, the number which are pregnant and their age.

“The survey is a vital tool for us to more or less just check-in and see how the dolphins are getting on.”

Angus said staff took small tissue samples from the dolphins to identify them using their DNA.

The size of the sample is just 2mm in diameter and 5mm long.

“We make sure the sampling has no effect on the dolphins and so far the indications are it hasn’t but we will keep on monitoring.

“We take the sample away, analyse it and we use that to gain information on the number, sex ratio, any pregnant females, the age structure.”

The abundance estimate work is done over the course of two consecutive summers. The 2021 work is the second year of this survey.

The work is undertaken in late summer and early autumn, when the dolphins are known to be in the area, allowing direct comparison between years to estimate the population size.

The DOC staff who carry out the survey will make 10 voyages, basing themselves and their vessel out of Raglan Harbour and Manukau Harbour.

DOC staff involved in the survey have already seen several calves which is an encouraging sign.

Angus said anyone who spots a Māui dolphin should leave them alone, but let DOC know.

Māui dolphins have a unique dorsal fin shaped like the ears of Mickey Mouse.

“Don’t seek the dolphins out please and if you do encounter them give them distance, slow down and just observe them but certainly we would want to hear about that encounter.”

Threats to Māui dolphins use to be from fishing but in 2020 a range of measures were brought in to protect them.

He said another threat was from toxoplasmosis which results from infection with a common parasite found in cat faeces and contaminated food.

It can threaten pregnant dolphins.

“If you have a cat, just take the cat pooh and dispose of it sensibly and don’t flush it down the drain because cat faeces could carry the disease.

“Although it might sound a little bit of a reach, we do know that the disease can reach the dolphins and can have an impact.”

He said because of the small number of Māui dolphins any impact should be reduced.

Angus said results should be available from the middle of 2021.