Despite fence, keeping Ka'ena Point predator-free is constant battle

Published On: Jun 11 2013 06:11:00 PM HST
KA'ENA POINT, Hawaii -

The predator fence at the Ka'ena Point Natural Reserve Area is a little more than two years old, but the benefits to native plants and sea birds is expected to last decades.

"We're really pleased with the outcome of the fence," said Marigold Zoll, Oahu natural area reserves manager with the state Department of Land and Natural Resources. "It's not going to happen overnight, full recovery, but we're well on our way to recovering this coastal habitat."

Finished in April 2011 at a cost of $290,000, the 6.5-foot fence was designed by Xcluder Pest Proof Fencing Company in New Zealand to keep out cats, rats, mice, mongooses and dogs from a 59-acre area at Ka'ena Point. The meshing is so fine, mice younger than four days can't get through.

But at the end of every rainy season mice tend to bloom, and some undoubtedly find their way around the fence's two weak points where meshing meets ocean. Keeping the area predator-free is a constant battle that involves baiting and trapping.

"It takes at least two people a full day of work every week to come out here and monitor the traps and make sure that we don't have any incursions," said Zoll. "If we do have an incursion, then we come out and trap like crazy (and) we run tracking tunnels to make sure that we've gotten all the animals."   

What used to be a landscape of desolate sand dunes at Ka'ena Point in the 1990s has been augmented by 11 species of native plants. Sea birds are also making a comeback, with shearwater chicks increasing from 300 before the fence was built, to 3,500 last year.

Meanwhile, the endangered Laysan albatross also continues to rebound, with 76 nest attempts and at least 30 chicks hatched during the most recent mating season, which begins every November.

"Albatross, they take a little longer to respond just because there wasn't as much of a predation issue, but they've gone up by about 15 percent. So, they're doing really well," said Lindsay Young, the Ka'ena predator fence project coordinator.  

The fencing is also allowing researchers to further study albatross in an effort to learn more about their habits during the first five years of life. Young, who's also a co-owner of the independent group Pacific Rim Conservation, attached devices to the legs of albatross chicks last month to plot their exact locations on the globe through the use of light levels.

"We know a lot about where adult albatrosses go, but the chicks, because they go to sea for three to five years, nobody knows what they're up to," said Young. "We're uniquely poised out here at Ka'ena Point to be able to retrieve those tags because birds come back in three to five years."

The predator fence has a life expectancy of 20 years, and is under a 5-year warranty. Young estimates it takes about $5,000 every year to maintain the fence, but the benefits are well worth the price.

"After 16 years, the cost of the fence, including the year-to-year maintenance, we'll break even versus the predator control that was going on before," explained Young. "And because the fence is expected to last longer than that, there's a financial benefit."

The Ka'ena Point Natural Reserve Area is open to the public year round, but visitors are told to stay on marked trails and leave their dogs at home. The predator fence features three access points with double sliding doors for added protection.

Zoll encourages anyone who hasn't visited the area to come spend a morning or afternoon at Ka'ena Point, which she says is like stepping back in time.

"This is the closest people will probably ever get to visiting the Northwestern Hawaiian Islands with the ground nesting sea birds and the intact coastal plant community," said Zoll.   


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