The map shows where the species may occur based on oceanography. The species has not been recorded for all the states within the hypothetical range as shown on the map. States for which confirmed records of the species exist are included in the list of native range states.
Habitat and Ecology
The habits and biology of Hector's dolphins in the South Island have been well studied in the last couple of decades (Dawson 2002) and there has been increasing research effort on
There is little information on the feeding ecology of
IUCN Red List Assessment
Red List Category
Red List Criteria
- 2000Critically Endangered
- 2000Critically Endangered
Studies of mitochondrial and nuclear DNA show that North Island Hector's dolphins are genetically distinct from any of the
Recent surveys show that the South Island Hector’s dolphin populations collectively number about 7,270 individuals (CV=15.8%; Dawson et al. 2004), while the
An age-structured model (Slooten et al. 2000) indicates that approximately 50% of Hector’s dolphins are mature individuals. If about half of the estimated 111
Population viability analyses using current abundance together with entanglement rates and historical and current fishing effort indicated a high risk of decline, and that gillnet entanglement had caused a decline since 1970 in the North Island subspecies population (Martien et al. 1999; Slooten 2007). Estimated abundance in the late 1990s was around 25% of the 1970 estimate of 437 individuals (Martien et al. 1999), and the most recent estimate of depletion is that about 7% of the 1970 population remains (Slooten 2007).
Like the species as a whole, Maui’s dolphin faces serious pressures from human activities. The main threat is entanglement in gillnets (Dawson et al. 2001; Slooten 2005; Slooten et al. 2006b). Of 14 stranded dolphins in which cause of death could be determined, seven had clear net markings, and an additional four had injuries suggestive of removal from nets (Dawson et al. 2001). Recreational gillnet fishing may be a more serious problem than commercial gillnet fishing, due to the proximity of Auckland, New Zealand’s largest city. Bycatches in trawl nets also have been reported. Additional potential threats include those listed for Hector’s dolphin, i.e. pollution, disease, vessel traffic and habitat modification (Stone and Yoshinaga 2000) although there is no direct evidence that pollution or disease is affecting this subspecies.
The species is listed in Appendix II of CITES.
The subspecies is restricted to waters of
The New Zealand Government has created a protected area for C. h. maui where gillnetting is prohibited along 390 km of coastline, but the area does not extend far enough south to cover the range of recent sightings and falls well short of covering the historic range. The latter has clear implications for the prospects of recovery. Gillnetting continues inside harbors, trawling is not restricted, and there are no observer programs to estimate the number of dolphins taken (Slooten et al. 2005, 2006b).
Discussions between the New Zealand Ministry of Fisheries and Department of Conservation are currently (early 2008) underway to develop a comprehensive management plan for Hector’s dolphin (including
Relevance to Humans and Ecosystems
IUCN Red List Category
Maui's dolphin or popoto (Cephalorhynchus hectori maui) is the world's rarest and smallest known subspecies of dolphin. They are a subspecies of the Hector's dolphin. Maui's dolphin are only found off the west coast of New Zealand's North Island. Hector's and Maui's are New Zealand's only endemic cetaceans. In 2012 an estimated 55 Maui's dolphins older than one year old were left in the world. Maui's dolphins are generally found close to shore in groups or pods of several dolphin. They are often seen in water shallower than 20 m deep, but may also range further offshore.
In 2012, the majority of a government-appointed panel of experts estimated that 4.95 Maui's dolphins were killed each year due to set-netting and trawling. In May 2014, the World Wildlife Fund in New Zealand launched "The Last 55" campaign, calling for a full ban over what it believed is their entire range. The International Whaling Commission supports more fishing restrictions, but the New Zealand government has resisted the demands and questioned the reliability of the evidence presented to the IWC that Maui's dolphins inhabit the areas they are said to inhabit. In June 2014, the government decided to open up 3000 km2 of the West Coast North Island Marine Mammal Sanctuary - the main habitat of the Maui's dolphin - for oil drilling. This amounts to one-quarter of the total sanctuary area.
In 2002, Maui's dolphins were classified as a subspecies of Hector's dolphin. Previously, they had been known as the North Island Hector's dolphin. Dr Alan Baker found genetic and skeletal differences in the Maui's dolphins which made them distinct from others in the Hector's species. These significant differences over a small geographical distance have not been found in any other studies of marine mammals. So far, 26 different mitochondrial DNA identification haplotypes have been found in the Hector's species, the Maui's ‘G' haplotype being one of them.
In 2002, Hector's dolphins were not known to be capable of swimming from the South Island to the North Island and co-existing with Maui's dolphins. Instead, the deep waters of the Strait were understood to have been an effective barrier between South Island Hector's and North Island Maui's subspecies for between 15,000 and 16,000 years. The 2012 Auckland University/Department of Conservation boat survey tissue sampling of Maui's in core range, which included historical samples, revealed three Hector's dolphins identified in this range area (two of them alive) along with another five Hector's being disclosed or sampled between Wellington and Oakura between 1967 and 2012.
No evidence so far indicates the Hector's and Maui's dolphins interbreed, but given their close genetic composition, they likely could. Interbreeding may increase the numbers of dolphins in the Maui's range and reduce the risk of inbreeding depression, but such interbreeding could eventually result in a hybridisation of the Maui's back into the Hector's species and lead to a reclassification of Maui's as again the North Island Hector's. Hybridisation in this manner threatens the Otago black stilt and the Chatham Islands' Forbes parakeet and has eliminated the South Island brown teal as a subspecies. Researchers have also identified potential interbreeding as threatening the Maui's with hybrid breakdown and outbreeding depression.
Maui's dolphins are only found off the west coast of the central North Island of New Zealand. Since 2001, the known range of the Maui's has been between the Kaipara Harbour south to Raglan Harbour. Most sightings of the dolphins are made in their core range about 30 km north and south of the Waikato River mouth. Old records remain of dolphin sightings off the east coast of the North Island between Wellington and the Bay of Plenty, which indicates more widespread and larger previous Maui's or Hector's populations. Historical presence has been confirmed by DNA analysis, dating back to Wellington Harbour in 1873.
A DOC survey report in 2012 estimated 55 adult Maui's dolphins remained. This is a marked decrease from a 2004 survey that found the population to be around 100 dolphins. A survey of Maui's dolphins in 1985 estimated their numbers to be at 134. The data from the 2012 report are not directly comparable with earlier aerial surveys because of the different methods used and the 2012 survey effort had concentrated on the area within one kilometre from shore, but the reports highlight that the population is very small and are indicative of a recent decline.
Whether some Maui's dolphins are migrating southwards, or only Hector's migrating northwards into Taranaki waters, is a matter of debate. A dolphin, either a Hector's or Maui's, was caught in Taranaki waters in a set net off Cape Egmont on 2 January 2012. A dolphin, DNA tested as a Hector's, was found washed up on the Opunake beach on 26 April 2012.
Cephalorhynchus dolphin sighting information released by DOC in September 2013 includes listing three public sightings of Hector's type dolphins along the coastline immediately north of Wellington in late 2011. Four other sightings occurred between Whanganui and Waitara in early 2012. Another sighting was recorded along the Poverty Bay coast of the North Island at this time. Sightings of this type of dolphin along the coast north of Wellington are infrequent, with the DOC database reporting only seven since 1970.
The migration of Hector's northwards from the South Island occurs but is not frequent. Hector's DNA was confirmed from strandings in 2005 at Peka Peka and in 1967 at Waikanae, along the Horowhenua coastline.
he DNA evidence of whether the Hector's were migrating from the east or west coasts of the South Island was inconclusive. A "potential for a small and elusive resident population of Hector's dolphins along the southern part of the North Island, outside the current range of the Maui's dolphin, or along the northern part of the South Island between the East and West Coast populations of Hector's dolphins..." was found.
During the 2012/2013 summer, the DOC conducted five aircraft and six boat searches, between New Plymouth and Hawera, without seeing any Maui's or Hector's dolphins. In the two years between July 2012 and July 2014, more than 900 MPI observer days had been conducted out to seven nautical miles from the Taranaki shoreline without sighting any Maui's or Hector's dolphins.
Ecology and behaviour
Vocalizations and echolocation
Foraging and predation
Maui's dolphins feed on small fish, squid, and ocean floor-dwelling species such as flatfish and cod. Maui's dolphins spend much of their time making dives to find fish on the sea floor. They also find fish and squid in midwater and at times feed near the surface.
Social behaviour and reproduction
Female Maui's dolphins are not sexually mature until they are 7 - 9 years of age. They then produce one calf every 2 - 4 years.
Very little is known about the Maui's dolphin reproductive physiology.
Since records began in 1921, 45 cases of deceased Maui's dolphins have been recorded, though at least six have turned out to be Hector's. According to the Department of Conservation's Incident Database, 31 of these dolphins either did not have their cause of death assessed or it was unknown. Six deaths were linked to possible or known net entanglement, six deaths to natural causes, and two deaths to human interaction.
Some groups in the fishing industry are against increased bans on set nets into waters further offshore and inside harbours, and say other factors are responsible for the decline in the population, including disease, pollution, mining, and natural predation.
Since the first major restrictions on commercial fishing to protect Maui's dolphins were imposed in 2003, 12 mortalities have been listed along the west coast of the North Island. Of these, three have been confirmed as Hector's and the deaths of all but one were from natural causes. The single death attributed to fishing occurred in January 2012. The most recent dolphin death reported was from old age, with no indications of fishing injury, and she was found on a beach near Dargaville on 13 September 2013. An analysis of microsatellite DNA shows the dolphin was a Maui's.
This DOC Incident Database information is contrary to a NABU paper submitted to the Scientific Committee of the International Whaling Commission in June 2013, which referred back to the database that the number of fatal Maui's entanglements in fishing nets has increased, from an average of one per year, to 1.33 per year, since 2008.
In 2006, Brucella was found in a dead Maui's dolphin and DOC says this bacterial infection could have serious ramifications for the small Maui's population. Brucellosis is a disease of terrestrial mammals that can cause late pregnancy abortion, and has been seen in a range of cetacean species elsewhere, though not so far in Hector's or Maui's dolphins.
In 2012, post mortem studies on Hector's and Maui's showed that most were infected with the protozoa Toxoplasma. Two of the three Maui's dolphins were killed by toxoplasmosis. Toxoplasmosis is known to reduce fertility in livestock, with cats playing a key role in its transmission. It is not known how toxoplasmosis spread to Maui's and Hector's dolphins, nor is any funding available for research into this. though Auckland City Council has decided to assist Massey University research by providing cat fecal samples.
In 2003, a ban on using commercial set nets was added to an existing ban on recreational set netting from Maunganui Bluff (north of Auckland) to Pariokariwa Point (north Taranaki), out to four nautical miles from shore. In 2008, the restriction on set netting was extended out to seven nautical miles from shore along the same coastal area. In 2008, the existing ban on trawling one nautical mile from this coast was extended to two nautical miles and extended to four nautical miles between Manukau Harbour and Port Waikato.
Set netting is prohibited inside the entrances of the Kaipara, Manukau and Raglan Harbours and Port Waikato. Current presence of Maui's further within these harbours is disputed, though they do visit the harbour mouths. After what MPI believed at the time in January 2012 was the capture of a Maui's dolphin off Taranaki (though now says it was 'about as likely as not' to have been a Hector's) in June 2012 the New Zealand government announced an interim set net ban extension south around the Taranaki coast to Hawera and out to two nautical miles from shore, and set netting only with government observers on board between two and seven nautical miles from land.
In November 2013, the Minister of Conservation Nick Smith, in finalising the Maui's dolphin Threat Management Plan, confirmed an increase of the Taranaki set net ban of two nautical miles, further out to seven nautical miles between Pariokariwa Point and Waiwhakaiho River near New Plymouth. He said this was due to five public sightings of Hector type dolphins off Waitara since 2006. Smith also announced codes of practice for seismic surveys would be implemented, regulations for inshore boat racing and the establishment of a Maui's dolphin Research Advisory Group.
DOC's 2014-2015 Conservation Services Programme provides for all set net vessels off Taranaki to continue to have MPI observers on board, with 420 days of MPI observer coverage budgeted for the year to 30 June 2015. Many of the trawl vessels in the area will also now have MPI observers on board to look for Maui's dolphins, with 300 observer days budgeted.
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