New Zealand’s endemic dolphins

Dolphins are often seen around the coast of Aotearoa New Zealand, but only two species – Hector’s and Māui – are endemic.

Similarities and differences

It is very difficult to distinguish these two species. In 2002, Māui dolphins were declared a separate subspecies of Hector’s dolphins due to their significant genetic and skeletal measurements. Māui dolphins have larger skulls than Hector’s dolphins and a longer wider rostrum, and they are often slightly smaller.

Both species have a unique feature – a rounded black dorsal fin instead of the more common curved and pointed fin that other dolphin species have around New Zealand's coast. Hector’s and Māui dolphins are revered as a taonga to Māori and are known by a variety of names including tutumairekurai, papakanua, upokohue, tukuperu, tūpoupou, pahu, pōpoto and hopuhopu.

Dolphins, like bats, use echolocation to provide a detailed image of their surroundings for navigation and hunting. Hector’s and Māui species communicate through short ultra-high-frequency clicks (generally too high for human hearing) and other methods, such as touching, visual clues, slapping their tail on the water or leaping into the air.

Hector’s dolphins are found almost exclusively around the coast of the South Island, but Māui dolphins are only found on the upper west coast of the North Island and there are far fewer of them.

Māui dolphins are in a perilous position. With a critically small population size, urgent intervention is needed to ensure their survival.

	Hector’s dolphin	Māui dolphin
Scientific name	Cephalorhynchus hectori hectori	Cephalorhynchus hectori maui
New Zealand Threat Classification System status	Nationally vulnerable	Nationally critical
Estimated population	15,000	57–75 (over 1 year old)
Length	1.5 m	1.2–1.7 m
Weight	40–60 kg	40–60 kg
Location	South Island (with rare North Island sightings)	West coast of the North Island from Maunganui Bluff to Whanganui
Lifespan	Up to 20 years, though potentially as old as 30	Up to 20 years, though potentially as old as 30

Māui dolphins

New Zealand’s endemic cetacean the Māui dolphin (Cephalorhynchus hectori maui) is the smallest and rarest dolphin in the world, classified in New Zealand as nationally critical. Department of Conservation 2016 data estimated that there are only 63 Māui dolphins over 1 year old remaining.

Māui dolphins do not start breeding until they are at least 6 years old and may only produce one calf every 2–3 years. This means that the best possible population growth rate is only about 2% a year. Both the Māui and Hector’s dolphins are not long lived, with a typical lifespan of only 20 years.

Threats

As a coastal species, our endemic dolphin species face a number of threats.

Pathogens

They are exposed to pathogens like Toxoplasma gondii and Brucella (which causes brucellosis). The Toxoplasma gondii parasite only reproduces sexually in cats (the definitive host), producing oocysts (eggs) that are released into the environment via cat faeces. The oocysts then end up in waterways that transport them out to sea. These pathogens have originated from land-based use, farmland run-off, pollution and sewage overflows from land and shipping. There has been evidence that T. gondii and Brucella pathogens have resulted in dolphin deaths and compromised dolphin health and breeding ability.

Human impacts

Other threats from humans in coastal areas include increased risk from fishing (particularly the use of gillnets), other diseases, oil and gas exploration, boat strike, seabed mining, coastal development, tourism and noise.

With such a small population of Māui dolphins, any threat is of serious concern.

Gathering data

Gathering population data of ocean species has many challenges. Researchers use a range of tools to help track population data over time. Tissue sampling allows researchers to identify individuals as well as the sex ratio and any pregnant females and to estimate the age structure of the population. Gathering small tissue samples has had no adverse effects on the dolphins sampled.

As the pigmented layer of their skin is quite thin, it can be easily damaged – sometimes leaving identifying scars. When up close, researchers can identify some individual dolphins using nicks in their dorsal fins, body scars (such as scars from shark attacks that they have escaped from) and/or skin colouration, though this only accounts for about 25% of identifications. Sometimes, the scars are from fishing equipment.

In an effort to gather crucial data to help prevent Māui dolphins from becoming extinct, a large fixed-wing drone has been developed to collect digital imagery and using artificial intelligence machine learning, to identify both Māui and Hector’s dolphins and autonomously detect animals in real time. This will allow researchers to conduct aerial surveys of dolphin populations or find and follow animals or pods to understand aspects of their behaviour. Read more about this ambitious project in this Stuff news article. At the start of 2023 this project received approval from the Civil Aviation Authority to use the drones beyond the visual line of sight, read more about this in this RNZ news story.

NIWA deployed acoustic moorings in 2017 in the core of the Māui dolphin’s habitat to try and discover how far offshore the dolphins are distributed and whether this changes seasonally. Each mooring carried two acoustic devices. A cetacean and porpoise detector (CPOD) recorded detections of the high-frequency clicks that the dolphins produce to hunt prey and navigate. The second device, a Soundtrap, recorded a subset of both clicks and whistles. This work was part of a joint Department of Conservation and Ministry for Primary Industries operation and the analysis was undertaken by the University of Auckland.

In addition to these data-gathering tools, the Department of Conservation asks for any dolphin sightings to be reported to them.

Other dolphin species

There are 15 other species of dolphins recorded around the New Zealand coast, the most commonly seen are: bottlenose, dusky, common, pilot whales and orca (commonly known as killer whales). Despite being called ‘whales’, killer whales and pilot whales are actually large members of the dolphin family. Find out more about whales around Antarctica, some of which visit New Zealand.

It always brings joy to see any species of dolphin frolicking in the sea, but always remember to stay a respectful distance from them. A final thought on dolphins from Albert Einstein.

There’s no question dolphins are smarter than humans as they play more.

Albert Einstein