NZ'S 10 most endangered species

New Zealand's population of Bryde's whales is unique because around 50 of its population can be found on the doorstep of a major city, Auckland. Photo / Supplied

New research shows the Maui's dolphin is sliding closer to extinction, but it is far from the only species struggling to cope in New Zealand's water, forests and rivers. Environment reporter Isaac Davison looks at 10 mammals and birds that are clinging to survival.

Top 5 birds

1. New Zealand Fairy Tern

Population: 35-40

Found: Lower half of Northland Peninsula, North Auckland beaches

Threats: Habitat loss and predation by rats, cats, dogs

The tiny, gutsy bird was thought to be disappearing when it dropped to 10 individuals - three or four capable of breeding - in 1983.

But the Wildlife Service, then the Department of Conservation intervened and the species recovered to around 40 individuals in 2008.

The fairy tern remains nationally critical, but there are some signs of hope - the likelihood of its extinction within 50 years has been lowered from 52 per cent to 39 per cent.

2. Kakapo

Population: 124

Found: Codfish Island (near Stewart Island) and Anchor Island (Fiordland)

Threats: Habitat loss and predation by rats, cats, and stoats

The flightless "parrot of the night" was once plentiful and with few natural predators it began nesting at ground level. This made it vulnerable to introduced predators and it is now nationally critical.

Now the large, long-living bird can only survive on island sanctuaries. The remaining kakapo produced just 11 chicks last year. But the charismatic, much-loved bird receives some of the most intense protective measures, with DoC investing $800,000 into its recovery every year. It also enjoys a high profile due to a star advocate called Sirocco and corporate backers such as mining company Rio Tinto.

3. Chatham Island Taiko

Population: 120-150

Found: Chatham Islands

Threats: Predation by cats, pigs, weka and rodents

One of the world's rarest seabirds, the ocean-wandering taiko was thought to be extinct after rapidly declining post-European contact. They were spotted by an amateur ornithologist in 1978, and 15 years later evidence of their breeding was found on the Chathams.

DoC sends trappers every year to control predators, and has set up a predator-proof fence around breeding grounds for when the birds return from the sea to nest. These measures have increased the number of breeding burrows to 17.

A trust has been set up on the island to ensure the taiko's long-term survival, and its members reported that attempts to create safe nesting burrows has so far been successful.

4. White Heron

Population: 100-140

Found: Wetlands across New Zealand (breeding site in Whataroa, north of Franz Josef glacier)

Threats: Predation by humans

Too beautiful for its own good, the white heron was hunted close to extinction by Maori and Pakeha who removed its striking plumage for ornamental feathers.

The bird is common in Australia, the South Pacific and Asia but was nearly killed off when its only breeding ground, on the West Coast of the South Island, was found.

This spot in Whataroa is now a protected reserve, and numbers have stabilised at around 120. The local population is sometimes bolstered by herons blown into our waters from Australia.

5. Black Stilt

Population: 150

Found: Mackenzie Basin, Canterbury

Threats: Habitat loss due to farming and hydroelectric development, predation by feral cats and ferrets, human interference

The jet-black and red-legged kaki, or black stilt, nearly disappeared into history in the 1980s after they were reduced to 23 individuals by introduced predators. Like many of our birds, they faced few predators pre-settlement and adopted habitats and habits which later made them vulnerable to introduced species.

Their main breeding ground in Canterbury has been impacted by draining wetlands and redirection of rivers. Despite intensive management and a captive breeding site near Twizel, they remain the world's rarest wading birds.

Top 5 mammals

1. Greater Short-Tailed Bat

Population: Unknown

Found: South of Stewart Island

Threats: Loss of habitat, predation by rats, stoats and cats

Like many New Zealand bats, the greater short-tailed bat was thought to have been killed off by introduced species and the logging of mature forests where it lived. It survived on offshore islands at the bottom of the country until rats also reached these havens. With no sightings since 1965 (there is only one known photograph of the bat, taken that year) it was considered extinct.

But bats have recently been sighted off Big South Cape (south of Stewart Island) that could be the greater short-tailed species. If the finding is confirmed, it could renew the drive to make these islands pest-free.

2. Maui's dolphin

Population: 55

Found: West coast of North Island

Threats: Gill nets and trawling nets

Maui's dolphin is in the conservation spotlight after a study last month found its numbers had dwindled to between 48 and 69 adults, down from 111 in 2004.

The finding has prompted the Government to widen a gill net ban and the West Coast marine sanctuary. But some are concerned it will take too long to be enforced. Extinction is expected if more than one dolphin is killed every five years, and two have died in the past five months.

Conservationists say there is no reason why the Maui's dolphin cannot recover, because its main threat - fishing - can be controlled. The only obstacle to a species recovery is public and political inertia.

Some biologists are more cynical of the need to preserve the Maui's, arguing that conservationists needlessly classed it as a sub-species of the Hector's dolphin (population 7000) to create more urgency in protecting dolphins.

3. Bryde's whale

Population: 160

Found: Hauraki Gulf, northeast of North Island

Threats: Ship-strike

New Zealand's population of Bryde's whales (pronounced Brooders) is unique because around 50 of its population can be found on the doorstep of a major city, Auckland.

This choice of habitat places the baleen whales - which grow to 15m and swim in shallow water - within the city's busy shipping corridor, and at least 15 whales have been killed in collisions with container vessels in the past 16 years. Scientists have suggested new shipping corridors and underwater alarms, but the most likely proposal to prevent ship-strike is slowing ships to below 12 knots.

4. Southern Elephant Seal

Population: 250-260

Found: Antipodes Island, Campbell Island, Auckland Island

Threats: Overfishing of prey, human interference

The enormous seals, which can weigh close to 400kg, are not threatened globally, but the New Zealand population is tiny. It has recovered from devastation at the hands of the 19th century sealers and is found in strong numbers on sub-Antarctic islands.

The seals are rare on New Zealand coastlines and DoC is concerned about harassment by humans or dogs when they come ashore. It is believed the seals could be impacted by ship-strike and overfishing of their prey.

5. New Zealand Sea Lion

Population: 12,000

Found: Auckland Islands, Campbell Islands, Otago Peninsula

Threats: Trawling nets and disease

Like the Maui's dolphin, the sea lion has come under intense scrutiny this year after research showed its numbers had halved since 1998. It has been classed as nationally critical and if its decline is not stemmed will be extinct within 23 years. A bacterial infection severely reduced breeding in 1997-98, and the species has failed to recover.

Its decline has been compounded by deaths due to squid fisheries, which trawl at a similar depth to the sea lions' hunting grounds. Conservation groups call the population decline a national emergency and are calling on stricter by-catch limits and a change in fishing methods.

The lucky few

In a country with 2800 threatened species, conservation in New Zealand is often about picking winners. The Department of Conservation's budget and energy can extend only to active interventions for 200 of these endangered species.

Whether a species is protected depends on funding, community input, national identity and research.

DoC spokesman Rory Newsam says interventions are often made because the department believes it can "get the most bang for its buck".

But animals and plants are not always invested in because they have a greater chance of survival. The kakapo receives a relatively large chunk of funding despite being functionally extinct on the mainland.

Some ecologists argue too much is spent rescuing the rare parrot, while more crucial parts of our ecosystem are left behind. But the kakapo is protected because it is a charismatic species and the public considers it integral to New Zealand's ecological identity.

Conservationists say kakapo are a window to New Zealand's history. They are believed to have inhabited the Earth for millions of years. To kill them off in a fraction of that time is an indictment on the way we live.