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Project to protect endangered seabird habitat and native plants on Lanai

Predator-proof fence covers nearly 80 acres of native forests

Construction of a fine-mesh predator-proof fence is underway, which will eventually enclose about 80 acres of Lanai's native forests and protect the endangered ‘ua‘u from feral cats and rats. PULAMA LANA‘I photo

Endangered Hawaiian seabird species whose biggest threats on Lanai are feral cats and rats are getting their habitats protected with a large predator-proof fence, covering nearly 80 acres of native forests.

To give the native ‘ua’u, or Hawaiian petrel, room to thrive in the upland areas of the island, the conservation team at Pulama Lana’i is installing a fine-mesh fence that will keep predators out, an effort that started in 2016 and finally began coming to life in late 2019 when crews broke ground.

“Hawaii is a special place, you know, everything from the native birds to the insects and tree snails and plants all evolved prior to people being here, and people brought a lot of other species here,” said Rachel Sprague, co-director of conservation for Pulama Lana’i, a private land management company. “Fencing, especially fencing like this that is a really fine mesh, it prevents rats or mice from being able to go through it or be able to climb it. We’re sort of creating islands within islands — trying to get back what Hawaii maybe used to look like before we brought rats and cats and deer here.”

This project “will be exciting” because it’s not just protecting the Hawaiian petrels that are critical to the ecosystem, but it’s also protecting a variety of native plants and insects, like the kahuli tree snails, Sprague said on Thursday afternoon.

“There’s all of these connections between native species that get disrupted when we introduce other species, but perpetuating those native species and being able to have a functioning system is not just preserving those natural histories of Hawaii, but that is also preserving cultural history,” she added. “All of those species are part of the cultural history of this place.”

An endangered ‘ua‘u, or Hawaiian petrel, rests in a burrow. PULAMA LANA‘I photo

The ‘ua’u are threatened by urbanization as well as stray cats that prey on these ground-nesting birds and by rats that destroy their eggs, Sprague told The Maui News.

Through a larger effort by the National Fish and Wildlife Foundation and local partners like Pacific Rim Conservation and others, Pulama Lana’i is hoping to create predator-free zones to restore endangered species and better understand their populations.

The Fish and Wildlife Service estimated that there are up to 30,000 petrels total living and breeding in the higher elevations and steep slopes of the main Hawaiian Islands, with Lanai hosting about a third of the population.

The conservation team has spotted only about 500 burrows hidden in thick vegetation underground, which is equivalent to a few thousand birds, but “we believe we only found about a tenth of what’s out there,” Sprague said.

“They only come in and out of their burrows at night, so they are a very hard species to study,” she said.

According to the National Park Service, known nests on Hawaii island are on the lower slopes of Mauna Loa where wildlife biologists estimate that only 50 to 60 breeding pairs are left there.

An estimated 4,000 breeding pairs are left among a population size between 8,000 to 10,000 petrels residing within Maui’s Haleakala National Park.

Funding for the nearly $1 million fencing project is provided by a National Fish and Wildlife Foundation grant and Pulama Lana’i. Construction of the fence that will surround a “core part” of the petrel colony is anticipated to be done in the middle of this year.

Sprague was hoping the project was going to be done a year ago, but some challenges caused by the COVID-19 pandemic slowed operations.

Once complete, this will be one of the larger conservation fences in the state, with one bigger project underway on Kauai, which shows a growing trend among Hawaii programs that are thinking about expanding beyond smaller 20- to 30-acre fencing projects, said Sprague.

Located just a couple miles from Lanai City, the predator-proof fence will cover 80 acres of the 90,000-acre island. The total ‘ua’u colony spans about 400 acres, so “there’s still work to do,” she said.

Nearly 1,000 humane rat and cat traps were also placed along 10 miles of trails as part of Pulama Lana’i’s ongoing predator control program.

Thousands of rats are controlled each year, Sprague said. Unlike Maui or other islands, Lanai does not have mongoose to worry about.

Residents are encouraged to keep their pets indoors — captured cats, domestic or stray, are typically taken to the Lanai Cat Sanctuary, which currently has over 600 cats, according to the website.

Trapping is effective in controlling predation, but not a “full fix” because these animals cannot be stopped from “getting into the colony where the birds live,” said Sprague.

Population trends are calculated by collecting call rates per minute over a long period of time via sound recorders as well as by monitoring burrows via nighttime infrared cameras.

These analytic tools will also help conservation teams to measure success of the fence by comparing before and after data.

“We do expect the fenced area is going to be a full restoration area where we will expect to see the success of the ‘ua’u to go up and our monitoring program is set up to be able to evaluate that,” Sprague said. “Given that it will be deer-free and rat-free, there are a number of endangered plants that are often eaten, so we think that we will be able to do habitat restoration and see positive impacts.”

However, conservation work is always ongoing and the team tries to formulate holistic solutions that focus on more than one species, she added, like how the ‘ua’u are the “catalyst for a really exciting project to happen and that will be able to protect 80 acres of our native forest.”

For more information about the project, email info@pulamalanai.com.

* Dakota Grossman can be reached at dgrossman@mauinews.com.

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