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The Hector’s Dolphin Endangered Animal Report 2010

Introduction Name: Hector’s dolphin

Museum in Wellington, Te Papa. He examined the

Scientific Name: Cephalorhynchus Hectori

first specimen found of the dolphin. The species was

Habitat: Coastal Waters

scientifically described by Belgian zoologist Pierre

Location: North And South Island

Joseph van Beneden in 1881.

Population: Approximately 7270

Primarily grey, black and white with a distinctive stripe running across its belly, this cetacean, air breathing,

Hector’s dolphins are the world’s smallest and rarest

water living mammal, is most recognizable by its lack

dolphins which are only found in New Zealand. The

of discernible beak and its round dorsal fin.

Hector’s dolphin is the smallest in the delphinidae family as well as the rarest oceanic species. Hector’s dolphin was named after Sir James Hector (1834 – 1907). He was the curator of the Colonial

The dolphin is classified as a vulnerable threatened species in the most recent IUCN, World Conservation Union, listings of globally threatened animal species.

‘Over the last thirty years New Zealand has lost on average 570 endangered Hector’s dolphins a year, that’s over 5,000 deaths each decade.’ WWF, 2010

Hector’s dolphin’s distribution 1/3 offshore distribution protected (Population continues to decline) Unprotected areas (Population continues to decline)

The problem Unprotected distribution Hector’s dolphins are endemic to the coastal

and in deeper water in winter, presumably in

regions of New Zealand and they have a patchy

response to movements of their prey species.

distribution around the entire South Island. The

The main populations are found between Motunau

species has a preference for shallow, coastal

and Timaru on the East Coast of the South Island,

waters less than 100m deep. This means they are

on the West Coast of the South Island, and in

most commonly seen close to shore, although

Foveaux Strait Te Waewae Bay area in Southland.

in shallow regions they have been sighted up to

Currently they are trapped accidentally in trawls

34km from the coast.

and gill nets. Some parts of their habitat have

In some areas, there is a pronounced seasonal

been protected, but to save this declining species,

difference in distribution, with dolphins being sighted further offshore

more areas around New Zealand will have to be declared no-go zones for coastal gill nets.


Population of Hector’s dolphin











Decrease of population from 1970–2010

Population decrease Scientists estimate that more than 26,000 Hector’s

dolphin species. The Cetacean Specialist Group of

dolphins lived around New Zealand’s shores in the

the Species Survival Commission of IUCN, the world

1970s. Today, it is thought that just 7270 remain

scientific experts on cetacean conservation, have

which is less than one third of the 1970s’ population.

assessed Hector’s dolphin as a threatened species

The Hector’s dolphin was given ‘threatened species’

of vulnerable status using the agreed threatened

status by the Department of Conservation in

species criteria. Research shows that even if all

December 1999.

available actions were implemented today, by 2055

Today, Hector’s dolphins are listed on the World Conservation Union’s Red List as endangered, and are among the most rare of the world’s 32 marine

the population would still be smaller than it was in 1970. The most likely outcome is that they will continue to decline, just at a slower rate than before.

‘Such very small population of Hector’s dolphins have a high extinction risk simply due to stochastic factors. Marine and Freshwater research, 2010


Number of dolphins









Hector’s dolphin’s mortality (1969–2009)

Mortality Mortality of Hector’s dolphin in gill-net fisheries is a

that was created in 1988, which reduces the amount

threat to local populations throughout its range. This

of gill net fishing. Conservation measures are most

population viability analysis extends previous work by

urgently needed for the highly threatened North Island

exploring a wider range of fishing levels and population

population, in particular the dolphins at the northern

growth rates, by incorporating year to year and

and southern end of this range.

environmental variability and by reporting results for

Reducing fisheries mortality to levels approaching zero

smaller population units.

shows the strongest promise of meeting national and

Ten of the 16 populations are likely to continue to

international guidelines for managing dolphin bycatch,

decline, five are indefinite, and one is likely to increase.

with a 59% probability of reaching 50% of estimated

All populations subjected to high fishing effort are

1970 population size by 2050.

declining. The only population predicted to increase is partly protected by a marine mammal sanctuary


Hector’s Dolphin


Hourglass Dolphin


Atlantic spotted Dolphin


Striped dolphin


Whiteside dolphin


Risso’s Dolphin

Shorter length, shorter life Hector’s Dolphins are one of the smallest dolphins in the world. As adults the Hector’s

species. By contrast, larger dolphins such as the bottlenose live to between 25 and 50 years.

Dolphin has a length of 1.5 meters and weigh

A dolphin’s age is estimated from the layers in a

in at only 50 kilograms.

cross section of tooth. Because of their small size,

Hector’s dolphins do not live as long as others, the smaller the species, the shorter the lifespan. Out of more than 80 Hector’s which have been dissected some of them caught in fishing nets, the oldest recorded ages have been 19 years for a female and 20 for a male. Some individuals may live longer than this, but the ages are comparable to those recorded for other Cephalorhynchus

they do not have enough reserves to make long journeys through fish starved oceans, to either populate other coasts or to mix with other of their kind. The lungs of a Hector’s dolphin are about the size of a human’s, and when trapped in one, it takes about the same length of time for them to drown as it would a person.


Number of dolphins







‘New zealand Hector’s dolphin populations are more susceptible to extinction than other species.’ Zoology and wildlife conservation, 1998

Hector’s Dolphin

Hour glass Dolphin

Striped Dolphin

Whiteside Dolphin

Risso’s Dolphin

Atlantic Spotted Dolphin

Population of different breeds

Life expectancy of endangered species Life expectancy Number of reproductions

50 yrs

4–8 yrs Humpback Whale

23 yrs

3–4 yrs Hooker’s Sea Lion

7–8 yrs

20 yrs

Hector’s Dolphin

The causes Breeding ovulation The slow rate of Hector’s dolphin’s reproduction

dolphins are having a very difficult time replacing

makes their populations vulnerable. Females aren’t

members of their population as fast as they are

sexually mature until they are between seven

losing them.

and nine years old, that would be equivalent to a

The gestation period for Hector’s Dolphin is believed

human not being able to reproduce until they are

to be about a year. Calves are born in spring and early

about 30 years old.

summer, November to February. The calf starts eating

They produce just one calf every two to four years.

solid food at about 6 months of age, but stays with its

One female might only produce four calves in her

mother for a full year. Minimum calving intervals range

20 year lifetime and this is just enough to replace

from 2 – 4 years, but the mother does not conceive

the number of dolphins that die naturally. Hector’s

again until the calf is independent.

Breeding ovulation Year 3

Calves are old enough to live on their own Nov

Year 2 Calves are born Nov

Mating season


Jan Year 1

Feb Mar









‘Fishing nets continue to kill Hector’s dolphins faster than they can breed.’ Global Voice for Wildlife, 2009

Death causes

73% Set net



13.5% Trawler


Cray pot

6.5% Trauma


Boat strike

Population declining threats Dolphins and people have shared our shores and

boats. Newborn dolphins are particularly

bays for centuries. In recent years, there has been a

vulnerable as they swim relatively slowly, close to

worldwide increase in awareness of marine mammals

the surface. Some have been killed by boat

and a greater desire to protect them.

propellers, when unwary boats have run them over.

Set net fishing poses a major threat to Hector’s

Other potential threats to their survival include

dolphins. Like all marine mammals they need to

trawling, marine pollution, disease and impacts

come to the surface regularly to breathe. If they

of tourism and aquaculture. They are also

become tangled in set nets, they will hold their

harmed by boat strikes, pollution and coastal

breath until they suffocate.

developments which degrade their habitat, and

Because these dolphins swim close to the shores and harbours, they are at risk of being injured by

future threats may arise from climate change, overfishing and aquaculture.

Commercial net Recreational net Unknown net


Number of dolphins











Reported net entanglements

Net sets Hector’s dolphins use echo-location to locate their

Set nets are the single most significant threat to

prey. Dolphins send out a stream of high frequency

the survival of Hector’s dolphins as the dolphins

clicking noises and when the sound strikes an object

get entangled in these nets and drown. Without

it bounces back and the dolphin can tell by listening

restrictions placed on commercial fishing, the risk of

what the object is, what kind of fish it is, how far

extinction of Hector’s dolphins would be very high.

away it is and how fast it is moving.

A 2008 report by the National Institute of Water

The dolphins cannot easily detect the nets, even

and Atmospheric Research (NIWA) estimates that

when using echolocation. This enables them to see

110 to 150 Hector’s dolphins die in commercial set

the hard parts of prey, or solid objects like rocks,

nets every year.

but because nets are soft and flexible they do not bounce sounds back to the dolphin.

‘Hector’s dolphin’s population today, is less than one-third of the 1970’s population.’ WWF, 2010



Strategy What needs to be done Specific ways in which protection could be improved

gill net and trawl fisheries continuing, in areas where

includes protection from gill nets and set nets,

Hector’s dolphins are found need to be considered.

allowing the Hector’s dolphins to recover. Better protection of harbours are needed.

We need to have a nationwide ban on gill nets in order to save the dolphins from extinction. This

Extending protection is needed on the west coast

means banning trawl fishing in waters less than 100

South Island to 6 nautical miles offshore, year-round.

meters deep in areas where Hector’s dolphins are

Also extending protection at Banks Peninsula area

found. Full protection is needed for dolphins across

offshore to 15 nautical miles as Hector’s dolphins

their entire range and for areas where they historically

are found well beyond the 4 nautical mile protection

ranged in the past.

boundary in this relatively shallow area. Increased protection from trawl fisheries and observers on all

‘The only population predicted to increase is partly protected by a marine mammal sanctuary which reduces the amount of gill net fishing.’ WWF, 2010

Protected distributions

What has already been done On 15 November 2007, the World Wide Fund for

mammals illegal. Under this act, the Department of

Nature launched an online petition asking Helen

Conservation designated the Banks Peninsula Marine

Clark, New Zealand’s Prime Minister at the time,

Mammal Sanctuary in 1988, effectively prohibiting

to introduce emergency measures to protect the

commercial gillnetting and restricting recreational

Hector’s dolphins. New measures were introduced

gill netting.

by the Ministry of Fisheries in 2008 effectively banning gill netting within 4 of the majority of the South Island’s east and south coasts, regulating gill netting on the South Island’s west coast out to 3.7km offshore and extending the gillnet ban on the North Island’s west coast to 13 km offshore. There are also restrictions on trawling in some of these areas. The New Zealand Marine Mammals Protection Act has made the deliberate killing or injury of marine

These were surpassed by new Ministry of Fisheries regulations in 2008 which ban gillnetting to four nautical miles off the majority of the South Island’s east and south coasts, regulate gillnetting on the South Island’s west coast to two nautical miles (3.7 kilometres) offshore. Five marine mammal sanctuaries were designated around the coastline in 2008 to provide additional protection from non fisheries related impacts

‘Total protection is the only way to give the dolphins the chance to recover so they are no longer at risk of extinction.’ Forest and Bird, 2010

Lisa Park | 06196330 Infographic design | 222.408

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