Wednesday, January 9, 2013

Rat plague hits penguins

Angela Pownall, The West Australian Updated January 9, 2013
Rat plague hits penguinsPenguin Island manager Dave Charles with a dead rat trapped on the island. Picture: Mogens Johansen/The West Australian
A plague of black rats is destroying the native wildlife population on Penguin Island, threatening to ruin one of WA's best nature havens and ecotourism attractions.

Thousands of the rats have inundated the small island 700m off Rockingham to feed on hundreds of eggs and chicks of its famous little penguin colony and other birds.

Penguin Island was, as ever, an idyllic escape from the heat and bustle of the mainland yesterday but the scene belied the huge environmental threat.

As families, tourists and holidaying children swam in the blue shallows and watched the penguins, birds and seals, a major offensive began to try to rid the island of its unwanted pests.

Penguin Island manager David Charles said the rats were having a devastating impact on wildlife.
"The bridled terns have had no chicks survive at all this year," he said. "From our nest boxes, we're talking about only 20 little penguin chicks that have survived.

"In previous years, it's been in the 40s and 50s."

The rat infestation is at a terrible time for WA's biggest breeding colony of little penguins, which already faces a battle for survival.

Mr Charles said the penguin population had fallen to 1200 breeding pairs from about 2000 just two years ago. Rising ocean temperatures are blamed for penguin deaths because the warmer waters drive away whitebait, their favourite food.

"We're not quite sure what we can do apart from eliminate as many of the factors that are affecting them as possible," Mr Charles said.

A dozen wildlife officers and volunteers are laying more than 270 poison bait traps over the 12.5ha island this week.

Black rats were first spotted on the island a year ago.

Mr Charles said a few rats were thought to have managed to cross the sandbar to the island at low tide or stowed away on a visiting boat.

In just one year, the number of rats has exploded to plague proportions and thousands now roam the island.

With a gestation period of just 21 days, female rats can have eight or nine litters of about six babies a year.

Mr Charles said they had designed the bait traps so only rats - and not skinks and other native wildlife - could get inside and take the poison.
Some secondary poisoning of birds that ate the dead rats was expected.

But Mr Charles said the mass rat poisoning was necessary to save the rest of Penguin Island's diverse wildlife.

Rat baiting program on Penguin Island


A black rat on Penguin Island. 
A black rat on Penguin Island.A DEPARTMENT of Environment and Conservation baiting program to eradicate black rats on Penguin Island will begin next week.

DEC Penguin Island manager David Charles said the invasive black rats were killing penguins, birds and other fauna on the island and had to be eradicated as soon as possible.
The island will remain open to the public during the six-week baiting phase, which starts on Monday.

“Black rats have recently become established on Penguin Island and are posing a significant threat to nesting shorebirds, seabirds, terrestrial birds and native skinks. The rats are also a serious threat to the island’s ecology,” Mr Charles said.

“The planned baiting program will involve using a commercially-available anticoagulant rat poison contained in bait stations and placed in a grid pattern around the island.

“The stations allow access by rats, but are designed to reduce the possibility of animals such as skinks getting into them."

Mr Charles said the baiting method would reduce the chances of native species being affected.

“Eradicating the rats will help protect Penguin Island’s diverse array of wildlife, including iconic little penguins, caspian terns, bridled terns and pelicans," he said.

“The island’s colony of little penguins is thought to be the largest on Australia’s west coast and of course, the island is very popular with tourists and for recreation activities. Another benefit of the baiting program will be the reduction of the introduced house mouse population.”

The baiting phase will run until the end of February. DEC staff will continue to monitor key species and the effectiveness of the program.

A biosecurity plan will also be developed and implemented to ensure black rats and other introduced animals and plants are not taken to Penguin Island in the future.

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