Spotting the smallest dolphins in the world

William Arlidge spent time aboard the DOC vessel Tuatini in February, keeping a keen eye out for Māui dolphins as part of the 2015 abundance estimate.

As a Technical Advisor in DOC’s Marine Species and Threats team I am fortunate to be working on a diverse range of research projects. Once in a while I also get the chance to get away from my desk and take part in some field research.

Earlier this year I flew up to Auckland and found myself boarding DOC’s research vessel, the Tuatini, to help out on the Māui dolphin population estimate.

Māui dolphin

Out on the water

Heading out of the Manukau Harbour we slowly navigated our way across the infamous sandbar and began searching south towards Port Waikato. We had great success in spotting dolphins along a small stretch of coastline immediately to the south of the Manukau Harbour entrance.

It was a fantastic experience to finally see such a rare and iconic New Zealand species in its natural environment.

During my days on the water I was tasked with recording data and spotting dolphins! I would position myself on the small vessel so I could monitor 360° as quickly and easily as possible.

Data sheets within easy reach and close enough to our skipper and fellow DOC employee Garry Hickman so he could hear any calls… “dolphin at three o’clock!”

A volunteer takes photos of a small pod of Māui dolphins during the 2015 survey

A New Zealand icon

The Māui dolphin, or popoto, is considered a taonga, or treasure, to Māori. They are found on the rugged west coast of the North Island and nowhere else in the world.

The Māui dolphin is increasingly being adopted as an icon of New Zealand’s marine environment and considered part of our cultural heritage.

Tips for spotting Māui dolphin

It is well known that Māui dolphins love to surf. Sightings of the little dolphins are often being reported from the beach, by surfers, or by boaties that are in close to shore as the dolphins catch a wave.

During the survey I would often scan the breaking waves for any sign of their characteristic fin, reminiscent of one of Mickey Mouse’s ears.

They are also easily identified by their small, black and grey patterned bodies. Growing to a maximum size of 1.7 meters long, they take the title of the smallest dolphin in the world!

The first group to help out on the Māui dolphin population estimate. Skipper Garry Hickman, William Arlidge (DOC); Scott Baker (Oregon State University); Lily Kozmian-Ledward (University of Auckland).

Researching Māui dolphin

The research that we were undertaking was building on research that began five years ago. In collaboration with the University of Auckland and Oregon State University, DOC began an abundance estimate on the critically endangered Māui dolphin.

We wanted to get a better idea of just how many of these small critters are out surfing the waves along our west coast beaches. Published in 2012, the population estimate results painted a dire picture for our beloved Māui dolphin.

The estimate showed only 48-69 dolphins over one year of age, with an average of 55 dolphins. This meant that the world’s smallest dolphin was also one of the most endangered dolphins in the world.

Five years on, an updated estimate was necessary to find trends in population movement. We also wanted to better inform the review of the Hector’s and Māui dolphin Threat Management Plan which will take place in 2018.

In collaboration with MPI, DOC is once again working with researchers from the University of Auckland and Oregon State University, to undertake this research.

Benefits of our research

To collect  information about the dolphins, we use a technique called genetic mark-recapture. It involves researchers taking tissue samples from a subset of the Māui dolphin population and then coming back at a later date (in our case a year) and re-sampling the population.

Recording data on DOC’s research vessel

The tissue samples taken are no bigger than an eraser on the end of a pencil and the wounds heal over in a couple of days.

The samples gather invaluable genetic information from each individual, and help us tell if the same dolphin has been sighted in the past. We can also find out the animal’s sex. If they are female, we can even look at progesterone levels to see if they’re pregnant.

Taking genetic samples is also important to tell Māui dolphins apart from their close relatives, Hector’s dolphins, which sometimes visit the Māui dolphin’s home range.

Māui and Hector’s dolphins look identical, but Māui dolphins are genetically different enough to be considered a separate subspecies. They have probably been a distinct population for about 16,000 years.

Māui dolphin

Hector’s dolphin

Results from our population estimate

Initial results from the first trip have now been analysed and show that the 48 samples collected represent 40 individuals. Two-thirds of these individuals were females. 38 individuals were identified as Māui dolphins with two individuals identified as Hector’s dolphins.

The characteristic fin, reminiscent of one of Mickey Mouse’s ears

While these initial results are encouraging and promise to provide a good basis for the study next February, it is still too early to know whether our treasured Māui dolphins are making any sort of comeback.

The final report of the updated population estimate is still a way off, but you can look forward to it being published in late 2016. Fingers crossed for a good result!