Taxonomy & Nomenclature
Physical Description / Field Identification
The typical robust Cephalorhynchus body shape is evident in this species. The head is blunt, the dorsal fin is low and rounded, and the flippers are rounded at the tips.
The predominant color of Hector's dolphin is light gray. The dorsal fin, flukes, flippers, area around the blowhole, and much of the face are dark gray to black. Ventrally, the animals are largely white. The lower part of the head, starting just behind the black lower jaw tip is white, as is the area from just behind the flippers to the urogenital area. Arms of white from this patch also extend part way up the sides. The white ventral patches can be invaded by black between the flippers, or can be completely separated by a continuous black area. There are also small white axillary and dark gray urogenital patches (the latter are smaller and not apparent in some females).
The mouth of a Hector’s dolphin contains 24-31 fine pointed teeth in each row.
Hector’s dolphin adults reach lengths of 1.5 m (females are slightly larger than males), and newborns are about 60-70 cm long. Weights of up to 57 kg have been reported.
Can be Confused With
Other dolphins (common, dusky, bottlenose, etc.) are found around New Zealand, but should be easy to distinguish from the small Hector’s dolphin, largely on the basis of dorsal fin shape.
This dolphin is endemic to New Zealand. They are found in shallow coastal waters, and are most common off the South Island and the west coast of the North Island. There are three genetically separate populations in the South Island, and the small North Island population has recently been named as a separate subspecies (C. h. maui in the North and C. h. hectori in the South).
Ecology and Behavior
The habits and biology of Hector’s dolphin have been well studied in the last few years. They live in groups of 2-8 individuals. Larger aggregations of up to 50 can be seen at times. These are active, sometimes acrobatic dolphins, and they are known to engage in bowriding activity. Photo-identification studies have demonstrated that at least some individuals are resident in small areas (about 30 km of coastline) year-round. Long-term associations between individuals are rare.
The calving season is in the spring through summer. Sexual maturity is reached at ages between 5 and 9 years, and adult females give birth every 2-4 years.
Feeding and Prey
Hector’s dolphins engage in opportunistic feeding on several species of small fish and squid.
Threats and Status
Recent surveys show that the South Island populations collectively number about 7,300 individuals, and the North Island population is feared to be under 100 animals. Hector’s dolphin faces serious pressures from human activities. Like its congeners, gillnets are the major concern, but unlike the others, the main problem in some areas is recreational gillnet fishermen. Up to 57 per year were known to have been caught in a small part of the range in the mid-1980s. That number has been reduced through legislation and the creation of a marine mammal sanctuary. Despite this, the species is still facing serious problems and is listed as ‘Endangered’, with the North Island population considered ‘Critically Endangered’ (IUCN). However, they are currently ‘Not Listed’ (ESA).
Baker, A.N., A.N.H. Smith and F.B. Pichler. 2002. Geographical variation in Hector’s dolphin recognition of new subspecies of Cephalorhynchus hectori. Journal of the Royal Society of New Zealand 32:713-727.
Dawson, S.M. 2002. Cephalorhynchus dolphins: Cephalorhynchus heavisidii, C. eutropia, C. hectori and C. commersonii. pp. 200-203 in W.F. Perrin, B. Würsig and J.G.M. Thewissen, eds. Encyclopedia of marine mammals. Academic Press.
Dawson, S., F. Pichler, E. Slooten, K. Russell and C.S. Baker. 2001. The North Island Hector’s dolphin is vulnerable to extinction. Marine Mammal Science 17:366-371.
Dawson, S.M. and E. Slooten. 1993. Conservation of Hector’s dolphins The case and process which led to establishment of the Banks Peninsula Marine Mammal Sanctuary. Aquatic Conservation Marine and Freshwater Ecosystems 3:207-221.
Pichler, F.B., S.M. Dawson, E. Slooten and C.S. Baker. 1998. Geographic isolation of Hector’s dolphin populations described by mitochondrial DNA sequences. Conservation Biology 12:676-682.
Slooten, E. and S.M. Dawson. 1994. Hector’s dolphin Cephalorhynchus hectori (van Beneden, 1881). pp. 311-333 in S.H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Volume 5: The first book of dolphins. Academic Press.
Slooten, E., D. Fletcher and B.L. Taylor. 2000. Accounting for uncertainty in risk assessment case study of Hector’s dolphin mortality due to gillnet entanglement. Conservation Biology 14:1264-1270.