Hector’s dolphins (Cephalorhynchus hectori hectori) are the smallest and rarest marine dolphins in the world and only found in New Zealand waters. Hector’s dolphin are known to Māori by many names, including tūpoupou, tutumairekurai, maui, aihe, papakanua, upokohue, tukuperu, pahu, popoto and hopuhopu.
A sub-species of the Hector’s dolphin is called the Maui dolphin (Cephalorhynchus hectori. Maui), which is only found on the west coast of the North Island and is critically endangered with a population between 57-75.
Hector’s dolphins can only be found around the coast of the South Island. Nationally they are considered vulnerable, but further research is required on their population size, distribution and specific subpopulation trends. It is known that their distribution is very fragmented as a result of having a small territorial range of about 50 km (they never go far from where they were born).
This fragmentation of the population with lost connectivity between subpopulations is a significant concern as this impacts the gene flow between larger core populations. Isolated subpopulations are more susceptible to threats from human activities and other stressors in their environment, which can reduce their capability to cope with issues such as disease. This likely means that the Queen Charlotte Sound / Tōtaranui subpopulation is critically endangered.
They are the only dolphins in New Zealand with a rounded black dorsal fin (shaped like a Mickey Mouse ear). Their bodies are a distinctive grey, with white and black markings and a short snout.
Adult Hector’s dolphins are less than 1.5 m in length and weigh between 40 and 60 kg with males being slightly smaller and lighter than females. At birth, Hector’s dolphin calves have a total length of around 60-80cm and weigh 8-10 kg, and resemble a rugby ball with fins.
Females reach sexual maturity between seven to nine years of age. They produce just one calf every two to three years, making population increase a very slow process.
Most females only have four or five calves in a lifetime. Calving usually occurs between November and mid February, and calves stay with their mothers for up to two years.
Hector’s dolphins use echolocation /sonar to find their food just like other dolphins, which is high frequency ‘clicks’ which bounce off surrounding objects such as seabed and fish, giving the dolphins a detailed picture of their surroundings.
Fishing is the main threat to the Hector’s population. Like all marine mammals they need to come to the surface regularly to breathe. If they become tangled in set nets, they will hold their breath until they suffocate.
Inshore coastal fisheries probably have a greater impact than oceanic fisheries, because Hector’s have a more restricted distribution than their oceanic relatives. According to the International Union for Conservation of Nature (IUCN), 60 per cent of all dead Hector’s dolphins, for which cause of death could be determined, had died as a result of gillnet entanglement.
Injury from boats is a risk because Hector’s dolphins live close inshore, often in bays and harbours. New born dolphins are particularly vulnerable as they swim relatively slowly, close to the surface so would be slow to get out of the way of a fast moving boat. Also the faster you go the less time the skipper has to see and avoid the the small new born dolphins.
Tūpoupou Marine Protected Area
The Tūpoupou Marine Protected Area is planned to be established in 2021 with the aim of protecting the breeding and birthing bays of the endangered Hector’s Dolphin / Tūpoupou on the west coast of Arapaoa (formerly Arapawa) Island. As an added benefit the proposed area is also one of the feeding grounds for the endangered King Shag / Kawau a toru.
The area is called Tūpoupou not only because that is one of the names for Hector’s Dolphin but it also means serious illness, an appropriate description for an ecosystem that needs help.