Maui and Hector’s dolphins are only found in New Zealand waters

They are rarer than kiwis and continue to be threatened by commercial and recreational fishing.

Key Points

  • New Zealand dolphins (Maui and Hector’s) are found only in New Zealand
  • Hector’s dolphin is the South Island subspecies
  • Maui dolphin is the North Island subspecies
  • Both are Endangered
  • Maui dolphin is Critically Endangered
  • There are fewer than 50 Maui’s dolphins left in the world
  • Entanglement in fishing nets is the number one threat
  • Fishing has caused major population declines
  • Current population size is less than 10% for Maui and 30% for Hector’s dolphin
  • Protection is not enough to help Maui’s or Hector’s dolphins recover
  • Protection urgently needs to be extended to all waters up to 100 m deep

New Zealand dolphins are easy to identify. No other dolphin has a rounded dorsal fin. The fins on most dolphins look more like a triangle, like a shark’s fin. NZ dolphins are very small, up to 1.4 metres long. Other dolphins are roughly human-size, about 2 metres long, or larger. NZ dolphins live in waters of up to 100 m depth.


There used to be more than 30,000 NZ dolphins, but now there are only around 10,000. NZ dolphin is only found in New Zealand and Trust researchers have surveyed the entire population. There are fewer than 50 Maui dolphins left in the world. These days, the population is fragmented into small local populations.

NZ dolphins have very large brains. This is reflected in their complex behaviour and social system. They live in small groups of 2-8 individuals, which sometimes get together into larger groups of 20-30, at times even 100 or so dolphins. The smaller groups of 2-8 individuals are usually made up of several males, or several females and their calves.

Their social system is usually described as ‘fission – fusion’. In other words, if two groups of dolphins meet, they don’t necessarily split up into their original groups again but may go onto form new and different groups when they go their separate ways.

NZ dolphins eat red cod, yellow-eyed mullet, stargazer, squid and a range of other species. We know that from examining stomach contents of dolphins that were found dead on beaches or caught in fishing nets.

Like most dolphins, NZ dolphins have a very slow reproductive rate. A female can expect to have her first calf when she is 7 to 9 years old, and she will have one calf every 2 to 3 years after that. That means an overall population growth rate of about 2%. In other words, a population of 100 NZ dolphins can grow by 2 individuals at most in any one year. That makes them very vulnerable to human impacts.

Conservation Problems and Solutions

The problem is very simple: Fishing nets kill dolphins. The solution is also very simple: We need to make the transition to dolphin-safe fishing methods. Even as late as 2006, between 110 and 150 NZ dolphins were killed in gillnets and trawl nets each year. Compared to other conservation problems, this one can be easily solved. We just need to change to selective, sustainable fishing methods that don’t catch dolphins. This will also help save many other protected species, like penguins, shags, shearwaters and other seabirds.

Dolphin protection is still not sufficient to provide effective protection. Current protection is shown in the map below, with NZ dolphin distribution shown in red, areas where dolphins are protected from gillnets and trawling shown in dark green, and areas where there is protection from gillnets only shown in light green

This second map shows the dolphin protection recommended by the IUCN:

Please write to the Minister of Fisheries, David Parker:

Asking him to follow the advice of the IUCN and protect NZ dolphins from both gillnets and trawling, throughout their habitat in all waters less than 100 metres deep.

Click here to find out more about the 100m Campaign.

The NZ Whale and Dolphin Trust’s research has been an important driving force in reducing threats to NZ dolphin, including the North Island sub-species Maui’s dolphin. Our research laid the foundations for NZ’s first protected area for marine mammals, the Banks Peninsula Marine Mammal Sanctuary (implemented by Helen Clark in 1988). We worked closely with the Department of Conservation to develop the sanctuary proposal, basing the north, south and offshore boundaries and fishing regulations within the sanctuary on our research data on dolphin distribution, fisheries mortality, etc. We frequently present our research information at public meetings with government officials and fishing industry representatives. We work actively with government and non-government organisations to achieve more effective protection for these endangered dolphins.

The Trust is continuing to support detailed research on the effectiveness of these protection measures. At this stage it is clear that the protection measures are a step in the right direction and have helped to slow down the rapid population decline. However, current protection is still insufficient to halt the declines in NZ dolphin populations, let alone allow them to to recover from the rapid decline of the last 50 years.

Maui’s dolphins are on the brink of extinction, with fewer than 50 individuals left. To avoid extinction of Maui’s dolphins, and to ensure NZ dolphins don’t keep sliding towards extinction, would mean following advice from the Scientific Committee of the International Whaling Commission and the IUCN:

In all areas where Maui and Hector’s dolphins are found, out to the 100 metre depth contour (the red area in the map above):

  1. Ban gillnets and trawl nets
  2. Encourage the fishing industry to make the transition to fishing methods that do not kill dolphins (including fish traps and hook and line fishing)

Research Papers

Distribution and abundance

Rayment, W., Clement, D., Dawson, S., Slooten, E., and Secchi, E. 2011. Distribution of Hector’s dolphin (Cephalorhynchus hectori) off the west coast, south island, New Zealand, with implications for the management of bycatch. Marine Mammal Science 27(2):398-420.

Rayment, W.J., Dawson, S.M. and Slooten, E. 2010. Seasonal changes in distribution of Hector’s dolphin at Banks Peninsula, New Zealand: implications for protected area design. Aquatic Conservation: Marine and Freshwater Ecosystems 20: 106-116.

Rayment, W. Dawson, S., and Slooten E. 2009. Acoustic monitoring of Cephalorhynchus dolphins with the T-pod: a case study with Hector’s dolphins in a marine protected area. Endangered Species Research. 10:333-339.

Rayment, W., Dawson, S.M., Slooten, E. and Childerhouse, S.J. 2006. Offshore distribution of Hector’s dolphin at Banks Peninsula. Department of Conservation Research and Development Series, 232, 23p.

Slooten, E., Dawson, S.M., and Rayment, W.J. 2006. Offshore distribution of Hector’s dolphins at Banks Peninsula: Is the Banks Peninsula Marine Mammal sanctuary large enough? NZ Journal of Marine and Freshwater Research 40(2):333-343.

DuFresne, S., Fletcher, D., and Dawson, S.M. 2006. Relative efficiency of line-transect survey designs for estimating abundance of inshore dolphins and porpoises. Journal of Cetacean Research and Management. 8(1): 79-85.

Slooten, E., Dawson, S.M., Rayment, W. J. and Childerhouse, S.J. 2006. A new abundance estimate for Maui’s dolphin: What does it mean for managing this critically endangered species? Biological Conservation 128: 576-581.

Slooten, E., Dawson, S.M., Rayment, W.J. and Childerhouse, S.J. 2005. Distribution of Maui’s dolphin, Cephalorhynchus hectori maui. New Zealand Fisheries Assessment Report 2005/28, 21p. Published by Ministry of Fisheries, Wellington.

Gormley A., Dawson, S.M., Slooten, E. Brager, S. 2005 Mark-recapture estimates of Hector’s dolphin abundance at Banks Peninsula, New Zealand. Marine Mammal Science. 21(2): 204-216.

Dawson, S.M., Slooten, E. DuFresne, S.D., Wade, P.R. and Clement, D.M. 2004. Small-boat surveys for coastal dolphins: Line-transect surveys of Hector’s dolphins (Cephalorhynchus hectori). Fishery Bulletin102(3): 441-451.M.

Slooten, E. Dawson, S.M. and Rayment, W.J. 2004. Aerial surveys for coastal dolphins: Abundance of Hector’s dolphins off the South Island west coast, New Zealand. Marine Mammal Science 20(3): 477-490.

Slooten, E., Dawson, S.M. and Rayment, W. 2002. Quantifying abundance of Hector’s Dolphins between Farewell Spit and Milford Sound. DOC Science Internal Series 35. 18pp. Department of Conservation, Wellington.

Clement, D., Slooten, E., Dawson, S.M. & DuFresne, S. 2002. Line-transect survey of Hector’s dolphin abundance between Farewell Spit and Motunau. DOC Science Internal Series 22. 15pp. Department of Conservation, Wellington.

Dawson, S.M. 2001. Fine-scale abundance estimates from the 2000/2001 aerial survey of Hector’s dolphins on the South Island west coast. DOC Science Internal Series 21. 9pp. Department of Conservation, Wellington.

DuFresne, S., Dawson, S.M. & Slooten. E. 2001. Hector’s Dolphin abundance: Southern line-transect surveys and effect of attraction to survey vessel. DOC Science Internal Series 1, 19pp.

Bejder, L. and Dawson, S.M. 2001. Abundance, residency and habitat utilisation of Hector’s dolphins in Porpoise Bay, New Zealand. New Zealand Journal of Marine and Freshwater Research 35: 277-287.

Dawson, S.M., Du Fresne, S., Slooten, E. & Wade, P.R. 2000. Line-transect survey of Hector’s dolphin abundance between Motunau and Timaru. Published Client report on contract 3072, funded by Conservation Services Levy. Department of Conservation, Wellington. 18pp.

Dawson, S.M. & Slooten, E. 1988. Hector’s Dolphin Cephalorhynchus hectori: Distribution and abundance. Rep. Int. Whal. Commn Special issue 9: 315-324.

Alongshore range, movement

Rayment, W., Dawson, S.M., Slooten, E., Brager, S., DuFresne, S. and Webster, T. 2009. Kernel density estimates of alongshore home range of Hector’s dolphins (Cephalorhynchus hectori) at Banks Peninsula. Marine Mammal Science. 25(3): 537-556.

Fletcher, D., Dawson, S.M. and Slooten, E. 2002. Designing a Mark-Recapture Study to Allow for Local Emigration. Journal of Agricultural, Biological and Environmental Statistics 7(4): 1-8.

Brager, S., Dawson, S.M., Slooten, E., Smith, S., Stone, G.S. and Yoshinaga, A. 2002. Site fidelity and along-shore range in Hector’s dolphin, an endangered marine dolphin from New Zealand. Biological Conservation 108: 281-287.

Population biology

Slooten, E. and Dawson, S.M. Assessing the effectiveness of conservation management decisions: Likely effects of new protection measures for Hector’s dolphin. Aquatic Conservation: Marine and Freshwater Ecosystems 20: 334-347. 2010

Slooten, E. 2007. Conservation in the face of uncertainty: Effectiveness of four options for managing Hector’s dolphin bycatch. Endangered Species Research 3:169-179.

Burkhart, S.M. and Slooten, E. 2003. Population viability analysis for Hector’s dolphin (Cephalorhynchus hectori): A stochastic population model for local populations. New Zealand Journal of Marine and Freshwater Research 37: 553-566

Slooten, E., Fletcher, D. & Taylor, B.L. 2000. Accounting for uncertainty in risk assessment: Case study of Hector’s dolphin mortality due to gillnet entanglement. Conservation Biology 14: 1264-1270.

Martien, K.K., Taylor, B.L., Slooten, E. Dawson, S.M. 1999. A sensitivity analysis to guide research and management for Hector’s dolphin. Biological Conservation 90: 183-191.

Cameron, C., Barker, R., Fletcher, D., Slooten, E. and Dawson, S. 1999. Modelling survival of Hector’s dolphins around Banks Peninsula, New Zealand. Journal of Agricultural, Biological and Environmental Statistics 4(2): 126-135.

Slooten, E., Dawson, S.M. and Lad, F. 1992. Survival rates of photographically identified Hector’s dolphins from 1984 to 1988. Marine Mammal Science 8(4): 327-343.

Slooten, E. and Lad, F. 1991. Population biology and conservation of Hector’s dolphin. Canadian Journal of Zoology 69: 1701-1707.


Slooten, E. 1991. Age, growth and reproduction in Hector’s dolphins. Canadian Journal of Zoology 69: 1689-1700.


Pichler, F., Baker, C.S., Dawson, S.M. & Slooten, E. 1998. Mitochondrial differences between east and west coast populations of Hector’s dolphin. Conservation Biology. 12(3): 1-8.

Sounds & acoustic behaviour

Rayment, W. Dawson, S.M. and Slooten, E. 2009. Trialling an automated passive acoustic detector (T-POD) with Hector’s dolphins (Cephalorhynchus hectori). Journal of the Marine Biological Association.Published online doi:10.1017/S0025315409003129.

Dawson, S.M. 1991. Clicks and Communication: The behavioural and social contexts of Hector’s dolphin vocalisations. Ethology 88(4): 265-276.

Thorpe, C.W., Bates, R.H.T. & Dawson, S.M. 1991. Intrinsic echolocation capability of Hector’s dolphin Cephalorhynchus hectori. J. Acoust. Soc. Am. 90(6): 2931-2934.

Thorpe, C.W. & Dawson, S.M. 1991. Automatic measurement of descriptive features of Hector’s dolphin vocalizations. J. Acoust. Soc. Am. 89(1): 435-443.

Dawson, S.M. & Thorpe, C.W. 1990. A quantitative analysis of the acoustic repertoire of Hector’s dolphin. Ethology 86: 131-145.

Dawson, S.M. 1988. The high-frequency sounds of free-ranging Hector’s dolphins Cephalorhynchus hectori. Rep. Int. Whal. Commn Special issue 9: 339-344.

Incidental catch

Dawson, S.M. & Slooten, E. 2005. Management of gillnet bycatch of cetaceans in New Zealand. Journal of Cetacean Research and Management. 7(1): 59-64.

Dawson, S.M. and Lusseau, D. 2005. Pseudoreplication problems in studies of dolphin and porpoise reactions to pingers. Marine Mammal Science 21(1). 175-176.

Dawson, S.M., Read, A.J. & Slooten, E. 1998. Pingers, porpoises and power: Uncertainties with using pingers to reduce bycatch of small cetaceans. Biological Conservation. 84(2):141-146.

Dawson, S.M. 1994. The potential for reducing entanglement of dolphins and porpoises with acoustic modifications to gillnets. Reports of the International Whaling Commission. Spec. Issue 15: 573-578.

Dawson, S.M. 1991. Incidental catch of Hector’s dolphins in inshore gillnets. Marine Mammal Science7(3): 283-295.

Dawson, S.M. 1991. Modifying gillnets to reduce entanglement of cetaceans. Marine Mammal Science7(3): 274-282.

Behaviour/Social organistion

Webster, T., Dawson, S.M., and Slooten, E. A simple laser photogrammetry technique for measuring Hector’s dolphins (Cephalorhynchus hectori) in the field. Marine Mammal Science 26(2): 296-308. 2010.

Webster, T., Dawson, S.M., and Slooten, E. Evidence for sex segregation in Hector’s dolphins (Cephalorhynchus hectori). Aquatic Mammals. 35(2): 212-219. 2009.

Brager, S, Chong, A., Dawson, S.M., Slooten, E. and W�rsig, B. 1999. A combined stereo-photogrammetry and underwater-video system to study group composition of dolphins. Helgol. Mar. Res. 53 (2): 122-128.

Slooten, E. 1994. Behavior of Hector’s dolphin: Classifying behavior by sequence analysis. Journal of Mammalogy 75: 956-964.

Slooten, E., Dawson, S.M. and Whitehead, H. 1993. Associations among photographically identified Hector’s dolphins. Canadian Journal of Zoology 71:2311-2318.

Tourist impacts

Bejder, L., Dawson, S.M. & Harraway, J. 1999. Responses of Hector’s dolphins to boats and swimmers in Porpoise Bay, New Zealand. Marine Mammal Science 15 (3): 738-750.


Jones, P.D., Hannah, D.J., Buckland, S.J., van Maanen, R., Leathem, S.V., Dawson, S., Slooten, E., van Helden, A. and Donoghue, M. 1999. Polychlorinated dibenzo-p-dioxins and polychlorinated biphenyls in New Zealand cetaceans. J. Cetacean Res. Manage. (Spec. Issue 1): 157-167.

Jones, P. D., Leathem, S. V., Hannah, D.J., Day, P.J., Dye, E.A., Hoffman, K.A., Lister, A.R., Porter, L.J., van Maanen, T., Symons, R.K., van Helden, A., Buckland, S.J., Slooten, E., Dawson, S.M. and Donoghue, M. 1996. Biomagnification of PCBs and 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans in New Zealand’s Hector’s dolphin. Organohalogen Compounds 29: 108-113.

Buckland, S.J., Hannah, D.J., Taucher, J.A., Slooten, E. and Dawson, S.M. 1990. Polychlorinated Dibenzo-p-dioxins and dibenzofurans in New Zealand’s Hector’s dolphin. Chemosphere 20: 1035-1042.

Hutton, J., Blair, D., Slooten, E., and Dawson, S.M. 1987. Case studies of fluke induced lesions in the mesenteric lymph node of Hector’s Dolphins (Cephalorhynchus hectori). Diseases of Aquatic Organisms2: 83-86.

Conservation biology, books & general reviews

Slooten E. and Dawson S.M. The conservation biology of an endangered species: Lessons learned for science and management. In Karzmarski, L (ed) Social Ecology of Dolphins, Monkeys and Apes: A Comparative Overview. Spinger. In press.

Slooten, E. and Dawson S.M. Sustainable levels of human impact for Hector’s dolphin. The Open Conservation Biology Journal 2, 37-43. 2008.

Dawson, S.M. Cephalorhynchus dolphins. in: “Encyclopedia of Marine Mammals” (Perrin, W.F., Wursig, B. & Thewissen, J.G.M, eds.). Academic Press. San Diego. 2nd Edition. In press.

Pichler, F.B. Slooten, E. and Dawson, S.M. 2003. Hector’s dolphins and fisheries in NZ: a species at risk. Pp. 153-173 in Marine Mammals: Fisheries, Tourism and Management issues. N.Gales, M. Hindell &qmp; R. Kirkwood, (eds), Melbourne University Press.

Dawson, S.M. 2002. Cephalorhynchus dolphins. pp. 200-203 In: “Encyclopedia of Marine Mammals” (Perrin, W.F., Wursig, B., Thewissen, J.G.M, eds.). Academic Press. San Diego.

Dawson, S.M., Slooten, E. Pichler. F., Russell, K. &qmp; Baker, C.S. 2001. North Island Hector’s dolphins are threatened with extinction. Marine Mammal Science 17(2): 366-371.

Dawson, S.M. and Slooten, E. 1996. The Downunder Dolphin: the story of Hector’s Dolphin. Canterbury University Press, Christchurch. 60pp.

Slooten, E. and Dawson, S.M. 1995. The Banks Peninsula Marine Mammal Sanctuary; a sanctuary within a sanctuary? In “Proceedings of the First International Conference on the Southern Ocean Whale Sanctuary” (Donoghue, M. ed.). Department of Conservation. Private Bag, Auckland.

Slooten, E. and Dawson, S.M. 1995. Conservation of New Zealand Marine Mammals. Pacific Conservation Biology 2(1): 64-76.

Slooten, E. and Dawson, S.M. 1994. Hector’s Dolphin. pp. 311-333 In “Handbook of Marine Mammals” Vol V, (Delphinidae and Phocoenidae: S.H Ridgway and R. Harrison, eds.). Academic Press. New York.

Dawson, S.M., and Slooten, E. 1993. Conservation of Hector’s dolphins: The case and process which led to establishment of the Banks Peninsula Marine Mammal Sanctuary. Aquatic Conservation 3: 207-221.

Dawson, S.M., and Slooten, E. 1992. Conservation of Hector’s dolphins: A review of studies which led to the establishment of the Banks Peninsula Marine Mammal Sanctuary. Canterbury Conservancy Technical Report Series 4. Department of Conservation, Canterbury.

Slooten, E. and Dawson, S.M. 1988. Studies on Hector’s Dolphin Cephalorhynchus hectori: A progress report. Rep. Int. Whal. Commn Special issue 9: 325-338.

Slooten, E. and Dawson, S.M. 1989. Hector’s dolphin: A case study for integrating conservation and fishing. In “Management of New Zealand’s Natural Estate” (D.A. Norton, ed.). Occasional Publication No. 1, New Zealand Ecological Society, Christchurch. pp. 112-114.

Dawson, S.M. 1985. The New Zealand Whale and Dolphin Digest. Brick Row Publishing. Auckland.130pp.