Please help us save Maui and Hector’s dolphins!

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

Urgent conservation needs

New Zealand dolphins (Hector’s and Maui dolphins) are found only in New Zealand. Hector’s dolphin is the South Island subspecies, Maui dolphin is the North Island subspecies.

They are Endangered due to deaths in fishing nets – gill nets and trawl nets. Maui dolphin is Critically Endangered because there are only 55 Maui dolphins left in the world. This is less than 10% of the original population size.

Maui dolphin is teetering on the brink of extinction and Hector’s dolphins are continuing to slide in the same direction. With about 10,000 individuals today, the South Island Hector’s dolphin population is less than 30% of its original numbers. To make matters worse, the population is highly fragmented into small local populations and fishing nets are removing these populations one at a time. Areas where they used to be very common are now without NZ dolphins.

We know that removing fishing nets from their habitat makes a huge difference. At Banks Peninsula, gillnets are banned up to 4 nautical miles from shore and trawling up to 2 nautical miles. Thrust researchers have found that this has increased their survival by more than 5%. The Banks Peninsula dolphin population had been declining at 6% per year and is now almost stable.

Extending protection to all waters up to 100 m deep would allow Hector’s and Maui dolphins to recover.

Behaviour and biology

New Zealand dolphins are only found in New Zealand and 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 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.

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 only males or only 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 on to 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 the 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 4 years after that. They only live to about 25 years. 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.

Where are we now?

Dolphin protection is not yet sufficient to provide effective protection. For example, around Banks Peninsula, on the east coast of the South Island, NZ dolphins range out to 20 nautical miles offshore but protection from gillnets only extends to 4 nautical miles (one nautical mile is 1.85 kilometres).


On the map above, dolphin sightings are shown as blue dots (winter) and red dots (summer distribution). The grey area is the protected area, where gillnets are not allowed to be used.

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 dolphin. Our research laid the foundations for NZ’s first protected area for marine mammals, the Banks Peninsula Marine Mammal Sanctuary (put in place 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, travel to Wellington to meet with politicians and government officials. We work actively with government and non-government organisations to achieve better protection for these endangered dolphins.

We are continuing to research the effectiveness of the Banks Peninsula Marine Mammal Sanctuary and develop plans for further protection measures. We were closely involved with research and public education leading to the creation of a protected area from Maunganui Bluff to Hawera for Maui dolphin. The first protected area for Maui dolphin was set up by Pete Hodgson (then Minister of Fisheries) in 2003.

In 2008, Jim Anderton (then Minister of Fisheries) put in place a comprehensive package of protection measures for Maui’s and Hector’s dolphins. Again, the Trust was at the forefront of this development, providing most of the research data and public education essential to reaching this goal.

This map shows the area where Hector’s dolphins live (red) and the area where they are now protected (green).

What needs to be done?

Much better protection is needed to allow NZ dolphin populations to recover from the rapid population declines of the last three decades.

Maui dolphins are on the brink of extinction, with only about 55 individuals left. Experience with the baiji (Chinese river dolphin) and vaquita (Mexican porpoise) show that when you get to such a low population size, a species can suddenly go extinct. To avoid extinction of Maui dolphins, and to ensure NZ dolphins don’t keep sliding towards extinction, we need to extend protection to all waters less than 100 metre deep (the red area in the map above).

Throughout NZ dolphin habitat, we need to:

  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)

Click here to view the Hope Spot Campaign.

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.