Hector's Dolphin
Encyclopedia
Hector's dolphin is the best-known of the four dolphin
s in the genus
Cephalorhynchus and is found only in New Zealand
. At about 1.4 m in length, it is one of the smallest cetacea
ns.
Hector’s dolphin was named after Sir James Hector
(1834–1907). He was the curator of the Colonial Museum in Wellington
(now the Museum of New Zealand Te Papa Tongarewa
). He examined the first specimen found of the dolphin. The species was scientifically described by Belgian zoologist Pierre-Joseph van Beneden
in 1881.
Maui's dolphin
(Cephalorhynchus hectori maui) is a subspecies
of Hector's dolphin found off the northwest coast of New Zealand's North Island
. It is the most endangered subspecies of marine mammal (other cetaceans with a similarly perilous conservation status inhabit rivers and estuaries only). There are approximately 110 Maui's dolphins remaining.
Māori names for Hector's and Maui's dolphin include Tutumairekurai, Tupoupou and Popoto.
Hector’s dolphin is the smallest of the delphinids. Mature adults have a total length of 1.2-1.6 m and weigh 40–60 kg. The species is sexually dimorphic, with females being slightly longer and heavier than males. The body shape is stocky, with no discernible beak. The most distinctive feature is the rounded dorsal fin, with a convex trailing edge and undercut rear margin.
The overall appearance is pale grey but closer inspection reveals a complex and elegant combination of colours. The back and sides are predominantly light grey, while the dorsal fin, flippers and flukes are black. The eyes are surrounded by a black mask, which extends forward to the tip of the rostrum and back to the base of the flipper. A subtly shaded, crescent shaped black band crosses the head just behind the blowhole. The throat and belly are creamy white, separated by dark grey bands meeting between the flippers. A white stripe extends from the belly onto each flank below the dorsal fin.
At birth, Hector’s dolphin calves have a total length of 60–80 cm and weigh 8–10 kg. Their coloration is the same as adults, although the grey has a darker hue. Four to six vertical pale stripes, caused by fetal folds affecting the pigmentation, are present on the calf’s body until an age of about 6 months.
. The species has a patchy distribution around the entire South Island
, although there are only very occasional sightings in the deep waters of Fiordland
. The centres of distribution are on the west coast between Kahurangi Point (41˚S) and Jacksons Bay (44˚S) and on the east coast around Banks Peninsula
(43˚S-44˚S). Maui’s dolphin is found only on the west coast of New Zealand’s North Island between 36˚S and 40˚S, with the majority of animals in the central portion of this range between the Manukau and Raglan Harbours.
Abundance has been estimated from a series of five line-transect surveys between 1998 and 2004. The abundance estimate for South Island Hector’s dolphin is 7270 (CV = 16%), and for Maui’s dolphin is 111 (CV = 44%). Current population size is estimated to be 27% of the abundance in 1970 before significant human impacts occurred.
The species has a preference for shallow, coastal waters less than 100 m deep. This means they are most commonly seen close to shore, although in shallow regions they have been sighted up to 34 km from the coast. In some areas, there is a pronounced seasonal difference in distribution, with dolphins being sighted further offshore and in deeper water in winter, presumably in response to movements of their prey species.
These life-history characteristics mean that Hector’s dolphins, like many other small cetaceans, have a low potential for population growth. Maximum population growth rate has been estimated to be 1.8-4.9% per year, although the lower end of this range is probably more realistic.
Hector’s dolphins are believed to be generalist feeders, with prey selection based on size rather than species. Stomach contents of dissected dolphins have included surface schooling fish, mid water fish and squid and a wide variety of benthic species. The largest prey item recovered from a Hector’s dolphin stomach was an undigested red cod weighing 500 g with a standard length of 35 cm.
Natural predators of Hector’s dolphins include sharks and probably orca
.
Conservation management for Hector’s dolphin has focussed on reducing gillnet bycatch. The first marine protected area
(MPA) for Hector's dolphin was designated in 1988 at Banks Peninsula
, where commercial gillnetting was effectively prohibited out to 4 n.mi. (7.4 km) offshore and recreational gillnetting was subject to seasonal restrictions. A second MPA was designated on the west coast of the North Island in 2003. Despite this protection, the Hector’s dolphin population was predicted to continue declining due to bycatch outside the MPAs.
On 15 November 2007, the World Wide Fund for Nature
launched an online petition asking Helen Clark
, New Zealand's Prime Minister at the time, to introduce emergency measures to protect the Hector's and Maui dolphins. New measures were introduced by the Ministry of Fisheries in 2008 effectively banning gillnetting within 4 n.mi. of the majority of the South Island’s east and south coasts, regulating gillnetting on the South Island’s west coast out to 2 n.mi. (3.7 km) offshore and extending the gillnet ban on the North Island’s west coast to 7 n.mi. (13 km) offshore. There are also restrictions on trawling in some of these areas. For further details on these regulations see the Ministry of Fisheries website. Five marine mammal sanctuaries were designated in 2008 to manage non-fishing related threats to Hector’s and Maui’s dolphin. Their regulations include restrictions on mining and seismic acoustic surveys.
New Zealand free-diver William Trubridge
referred to his goal to make the first 100m single breath unassisted
dive as "Project Hector" to draw attention to Hector's dolphin. He successfully achieved the dive on December 13, 2010, setting a new world record.
A mere three days later Trubridge would surpass his own goal by setting a new world record of 101 meters in a no fins dive on December 16, 2010.
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...
s in the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Cephalorhynchus and is found only in New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. At about 1.4 m in length, it is one of the smallest cetacea
Cetacea
The order Cetacea includes the marine mammals commonly known as whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general. It comes from Ancient Greek , meaning "whale" or "any huge fish or sea...
ns.
Hector’s dolphin was named after Sir James Hector
James Hector
Sir James Hector was a Scottish geologist, naturalist, and surgeon who accompanied the Palliser Expedition as a surgeon and geologist...
(1834–1907). He was the curator of the Colonial Museum in Wellington
Wellington
Wellington is the capital city and third most populous urban area of New Zealand, although it is likely to have surpassed Christchurch due to the exodus following the Canterbury Earthquake. It is at the southwestern tip of the North Island, between Cook Strait and the Rimutaka Range...
(now the Museum of New Zealand Te Papa Tongarewa
Museum of New Zealand Te Papa Tongarewa
The Museum of New Zealand Te Papa Tongarewa is the national museum and art gallery of New Zealand, located in Wellington. It is branded and commonly known as Te Papa and Our Place; "Te Papa Tongarewa" is broadly translatable as "the place of treasures of this land".The museum's principles...
). He examined the first specimen found of the dolphin. The species was scientifically described by Belgian zoologist Pierre-Joseph van Beneden
Pierre-Joseph van Beneden
Pierre-Joseph van Beneden was a Belgian zoologist and paleontologist.Born in Mechelen, Belgium, he studied medicine at the University of Louvain, and studied zoology in Paris under Georges Cuvier...
in 1881.
Maui's dolphin
Maui's dolphin
Maui's dolphin is the world's smallest known species of dolphin. They are a sub-species of the Hector's dolphin....
(Cephalorhynchus hectori maui) is a subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
of Hector's dolphin found off the northwest coast of New Zealand's North Island
North Island
The North Island is one of the two main islands of New Zealand, separated from the much less populous South Island by Cook Strait. The island is in area, making it the world's 14th-largest island...
. It is the most endangered subspecies of marine mammal (other cetaceans with a similarly perilous conservation status inhabit rivers and estuaries only). There are approximately 110 Maui's dolphins remaining.
Māori names for Hector's and Maui's dolphin include Tutumairekurai, Tupoupou and Popoto.
Physical description
The overall appearance is pale grey but closer inspection reveals a complex and elegant combination of colours. The back and sides are predominantly light grey, while the dorsal fin, flippers and flukes are black. The eyes are surrounded by a black mask, which extends forward to the tip of the rostrum and back to the base of the flipper. A subtly shaded, crescent shaped black band crosses the head just behind the blowhole. The throat and belly are creamy white, separated by dark grey bands meeting between the flippers. A white stripe extends from the belly onto each flank below the dorsal fin.
At birth, Hector’s dolphin calves have a total length of 60–80 cm and weigh 8–10 kg. Their coloration is the same as adults, although the grey has a darker hue. Four to six vertical pale stripes, caused by fetal folds affecting the pigmentation, are present on the calf’s body until an age of about 6 months.
Population and distribution
Hector's dolphins are endemic to the coastal regions of New ZealandNew Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. The species has a patchy distribution around the entire South Island
South Island
The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south and east by the Pacific Ocean...
, although there are only very occasional sightings in the deep waters of Fiordland
Fiordland
Fiordland is a geographic region of New Zealand that is situated on the south-western corner of the South Island, comprising the western-most third of Southland. Most of Fiordland is dominated by the steep sides of the snow-capped Southern Alps, deep lakes and its ocean-flooded, steep western valleys...
. The centres of distribution are on the west coast between Kahurangi Point (41˚S) and Jacksons Bay (44˚S) and on the east coast around Banks Peninsula
Banks Peninsula
Banks Peninsula is a peninsula of volcanic origin on the east coast of the South Island of New Zealand. It has an area of approximately and encompasses two large harbours and many smaller bays and coves...
(43˚S-44˚S). Maui’s dolphin is found only on the west coast of New Zealand’s North Island between 36˚S and 40˚S, with the majority of animals in the central portion of this range between the Manukau and Raglan Harbours.
Abundance has been estimated from a series of five line-transect surveys between 1998 and 2004. The abundance estimate for South Island Hector’s dolphin is 7270 (CV = 16%), and for Maui’s dolphin is 111 (CV = 44%). Current population size is estimated to be 27% of the abundance in 1970 before significant human impacts occurred.
The species has a preference for shallow, coastal waters less than 100 m deep. This means they are most commonly seen close to shore, although in shallow regions they have been sighted up to 34 km from the coast. In some areas, there is a pronounced seasonal difference in distribution, with dolphins being sighted further offshore and in deeper water in winter, presumably in response to movements of their prey species.
Ecology and life history
Bycaught and stranded Hector’s dolphins have provided information on the life history and reproductive parameters of the species. The maximum observed age is 19 years for females and 20 years for males. However, a long term photo-ID project at Banks Peninsula has shown that individuals reach at least 23 years old. Males attain sexual maturity between five and nine years of age, and females have their first calf between seven and nine years old. The calving interval is two to four years.These life-history characteristics mean that Hector’s dolphins, like many other small cetaceans, have a low potential for population growth. Maximum population growth rate has been estimated to be 1.8-4.9% per year, although the lower end of this range is probably more realistic.
Hector’s dolphins are believed to be generalist feeders, with prey selection based on size rather than species. Stomach contents of dissected dolphins have included surface schooling fish, mid water fish and squid and a wide variety of benthic species. The largest prey item recovered from a Hector’s dolphin stomach was an undigested red cod weighing 500 g with a standard length of 35 cm.
Natural predators of Hector’s dolphins include sharks and probably orca
Orca
The killer whale , commonly referred to as the orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas...
.
Conservation
Bycatch in bottom-set gillnets has been responsible for the majority of human induced mortality of Hector’s dolphins. The nationwide estimate for bycatch in commercial gillnets is 110-150 dolphins per year which is far in excess of the level which is considered to be sustainable. Hector’s dolphins face a range of other impacts including trawl bycatch, tourism, pollution and habitat modification.Conservation management for Hector’s dolphin has focussed on reducing gillnet bycatch. The first marine protected area
Marine Protected Area
Marine Protected Areas, like any protected area, are regions in which human activity has been placed under some restrictions in the interest of conserving the natural environment, it's surrounding waters and the occupant ecosystems, and any cultural or historical resources that may require...
(MPA) for Hector's dolphin was designated in 1988 at Banks Peninsula
Banks Peninsula
Banks Peninsula is a peninsula of volcanic origin on the east coast of the South Island of New Zealand. It has an area of approximately and encompasses two large harbours and many smaller bays and coves...
, where commercial gillnetting was effectively prohibited out to 4 n.mi. (7.4 km) offshore and recreational gillnetting was subject to seasonal restrictions. A second MPA was designated on the west coast of the North Island in 2003. Despite this protection, the Hector’s dolphin population was predicted to continue declining due to bycatch outside the MPAs.
On 15 November 2007, the World Wide Fund for Nature
World Wide Fund for Nature
The World Wide Fund for Nature is an international non-governmental organization working on issues regarding the conservation, research and restoration of the environment, formerly named the World Wildlife Fund, which remains its official name in Canada and the United States...
launched an online petition asking Helen Clark
Helen Clark
Helen Elizabeth Clark, ONZ is a New Zealand political figure who was the 37th Prime Minister of New Zealand for three consecutive terms from 1999 to 2008...
, New Zealand's Prime Minister at the time, to introduce emergency measures to protect the Hector's and Maui dolphins. New measures were introduced by the Ministry of Fisheries in 2008 effectively banning gillnetting within 4 n.mi. of the majority of the South Island’s east and south coasts, regulating gillnetting on the South Island’s west coast out to 2 n.mi. (3.7 km) offshore and extending the gillnet ban on the North Island’s west coast to 7 n.mi. (13 km) offshore. There are also restrictions on trawling in some of these areas. For further details on these regulations see the Ministry of Fisheries website. Five marine mammal sanctuaries were designated in 2008 to manage non-fishing related threats to Hector’s and Maui’s dolphin. Their regulations include restrictions on mining and seismic acoustic surveys.
New Zealand free-diver William Trubridge
William Trubridge
William Trubridge is a world champion and double world record holding free-diver from New Zealand.Trubridge currently holds the world record in the Free Immersion and the Constant Weight without fins disciplines, and is the first human ever to break the 100m barrier unassisted.World Records:•...
referred to his goal to make the first 100m single breath unassisted
Constant Weight without fins
Constant Weight Without Fins is an free-diving discipline in which the free-diver descends and ascends by swimming without the use of fins or without pulling on the rope or changing his ballast; only a single hold of the rope to stop the descent and to start the ascent is allowed...
dive as "Project Hector" to draw attention to Hector's dolphin. He successfully achieved the dive on December 13, 2010, setting a new world record.
A mere three days later Trubridge would surpass his own goal by setting a new world record of 101 meters in a no fins dive on December 16, 2010.
Specimens
- MNZ MM001915, collected Kaikoura, New Zealand, no date data.
Further reading
- National Audubon Society: Guide to Marine Mammals of the World ISBN 0-375-41141-0
- Encyclopedia of Marine Mammals ISBN 0-12-551340-2
- Whales, Dolphins and Porpoises, Mark Carwardine 1995 ISBN 0-7513-2781-6
- Facts about Maui's dolphin Department of Conservation - Several Images & listed as 'critically endangered' - Retrieved 2007-05-08.
- Hector's Dolphins, New Zealand Ministry of Fisheries - Retrieved 2007-02-09.
- Hector's Dolphin - Factsheet, Royal Forest and Bird Protection Society of New ZealandRoyal Forest and Bird Protection Society of New ZealandThe Royal Forest and Bird Protection Society of New Zealand Inc. is an environmental organisation specialising in conservation of indigenous plant and animal life in and around New Zealand....
Inc - Retrieved 2007-02-09.