Natural born killers stalk Kiwi birdlife

Stoats have wreaked havoc on the birds of New Zealand. Now conservationists are fighting back

By Kathy Marks

In Britain, stoats are part of the rhythm of nature. They prey on rabbits and rats; they are preyed on by foxes and eagles. In New Zealand, whose only land mammals were two species of bats until Europeans arrived, stoats are the single biggest threat to the unique and increasingly threatened native birdlife.

 

A world leader in conservation, New Zealand has saved some of its rarest birds from extinction by ridding off-shore islands of predators. Stoats, which can swim, were thought to have a maximum range of 1.5 kilometres (less than a mile). Recently, though, the sleek, furry killers have turned up on an island more than five kilometres from the mainland, raising questions about the safety of offshore sanctuaries.

Many of New Zealand's birds live and nest on the forest floor. Some, such as kakapo, weka and kiwi, are flightless. When they feel under threat, they freeze, making them easy prey for animals such as rats, cats and ferrets. Stoats – introduced in 1884 to combat a rabbit plague – are particularly formidable predators. They can tackle animals 10 times their body weight; they hunt by day as well as at night; they can travel vast distances, climb trees, and survive in almost any habitat. They are also prolific breeders, and they kill far more than they need to satisfy their hunger.

"When stoats get into a seabird colony or chicken hutch, they kill everything," says Andrew Veale, an expert on stoat genetics at Auckland University. He cites credible reports of a moorhen being attacked by a stoat and taking off into the air, with the stoat still attached. Dr Veale says: "They are phenomenal killers, with an immense bite strength."

More than 80 of New Zealand's offshore islands are pest-free sanctuaries where all mammals have been removed through trapping, shooting, and dropping poison from helicopters. Last year, a stoat was found on Rangitoto Island, more than three kilometres off Auckland. The island had been declared predator-free only a year earlier, following a NZ$3m (£1.6m) eradication programme. By analysing the stoat's DNA, Dr Veale established that it was from the mainland. This year, three stoats have been trapped on Kapiti island, a wildlife reserve 5.2 kilometres off Wellington. Dr Veale believes a female swam over and gave birth.

Read on...

Shocking images: possums and stoats eat kea chicks

Cameras catch predators invading defenceless nests

November 2010: New evidence shows possums are eating New Zealand's native parrot, the kea. Researchers using nest-cameras have for the first time witnessed the gruesome reality inside defenceless kea nests invaded by stoats and possums in South Westland.

Brent Barrett, from the Department of Conservation, says large numbers of kea nests are failing in the wild but it is only now that camera equipment has been able to uncover what's going on.

‘We are just midway through the breeding season and of 11 nests we've had under surveillance three have been devastated by stoats and possums. That's a loss of six chicks.'

Mr Barrett said photos and videos have been posted on YouTube under the key words ‘possums eat parrots' so that people can see for themselves exactly what is going on in kea nests.


Grisly surprise to see such a prolonged and tormented death.
‘We have never been able to look at kea nests in this way before and it was a grisly surprise to see photos of a possum eating a nearly fledged kea and video showing the prolonged and tormented death of chicks attacked by stoats,' Mr Barrett said.

‘Possums have previously been filmed killing an adult kaka but until now we were completely unaware of their direct impact on kea nests,' he said. ‘This constitutes a huge risk to our lowland populations as nearly all of our nests are being visited by possums.'

Mr Barrett said it has been distressing to discover that just how long it takes chicks to die during a prolonged attack by stoats.

‘One attack lasted two-and-a-half hours with the stoat remaining in the recesses of the nest hole and repeating its assault on the two dying chicks. One chick died at the end of the torment but the other lived for 40-hours with its injuries before disappearing. The mother was also injured.'

The stoat predation footage was captured at a nest south of Fox Glacier and the possum was photographed in Okarito Forest.

This is what happens when predators are not controlled

‘The YouTube footage is unpleasant stuff to watch, but it shows what's going on in places where predators are not controlled,' Mr Barrett said.

The kea research team is monitoring nests in the Okarito Forest and in the area from the Copland Valley to the Paringa River, south of Fox Glacier. These areas are steep and thickly forested making it difficult to track wild kea and carry camera equipment and large batteries around in.

‘We are all relieved that the effort is worth it, but saddened by the graphic nature of what we have found,' Mr Barrett said.

Researchers are also monitoring trees for signs of excessive fruiting which would trigger a chain of events starting with a rat plague and ending with a plague of stoats.

‘We are still in the process of gathering this information, but at the moment it looks like we may have a moderate rimu fruiting coming up,' Mr Barrett said.

http://www.wildlifeextra.com/go/news/kea-possum.html

Shocking images: possums and stoats eat kea chicks

Cameras catch predators invading defenceless nests

November 2010: New evidence shows possums are eating New Zealand's native parrot, the kea. Researchers using nest-cameras have for the first time witnessed the gruesome reality inside defenceless kea nests invaded by stoats and possums in South Westland.

Brent Barrett, from the Department of Conservation, says large numbers of kea nests are failing in the wild but it is only now that camera equipment has been able to uncover what's going on.

‘We are just midway through the breeding season and of 11 nests we've had under surveillance three have been devastated by stoats and possums. That's a loss of six chicks.'

Mr Barrett said photos and videos have been posted on YouTube under the key words ‘possums eat parrots' so that people can see for themselves exactly what is going on in kea nests.


Grisly surprise to see such a prolonged and tormented death.
‘We have never been able to look at kea nests in this way before and it was a grisly surprise to see photos of a possum eating a nearly fledged kea and video showing the prolonged and tormented death of chicks attacked by stoats,' Mr Barrett said.

‘Possums have previously been filmed killing an adult kaka but until now we were completely unaware of their direct impact on kea nests,' he said. ‘This constitutes a huge risk to our lowland populations as nearly all of our nests are being visited by possums.'

Mr Barrett said it has been distressing to discover that just how long it takes chicks to die during a prolonged attack by stoats.

‘One attack lasted two-and-a-half hours with the stoat remaining in the recesses of the nest hole and repeating its assault on the two dying chicks. One chick died at the end of the torment but the other lived for 40-hours with its injuries before disappearing. The mother was also injured.'

The stoat predation footage was captured at a nest south of Fox Glacier and the possum was photographed in Okarito Forest.

This is what happens when predators are not controlled

‘The YouTube footage is unpleasant stuff to watch, but it shows what's going on in places where predators are not controlled,' Mr Barrett said.

The kea research team is monitoring nests in the Okarito Forest and in the area from the Copland Valley to the Paringa River, south of Fox Glacier. These areas are steep and thickly forested making it difficult to track wild kea and carry camera equipment and large batteries around in.

‘We are all relieved that the effort is worth it, but saddened by the graphic nature of what we have found,' Mr Barrett said.

Researchers are also monitoring trees for signs of excessive fruiting which would trigger a chain of events starting with a rat plague and ending with a plague of stoats.

‘We are still in the process of gathering this information, but at the moment it looks like we may have a moderate rimu fruiting coming up,' Mr Barrett said.

http://www.wildlifeextra.com/go/news/kea-possum.html