Lehua Islet declared rat-free

LIHU‘E — After decades of work, Lehua Island, the tiny island off Ni‘ihau and Kaua‘i’s west shore, has been declared free of damaging, introduced, invasive rats, enabling Hawai‘i’s seabirds to safely nest on the steep, rocky cliffs, and native plants to flourish once again.

“After extensive on-island monitoring, we’re 99.99% certain there are no more rats on Lehua, which builds on the successful removal of invasive herbivorous rabbits and secures a future for Hawai‘i’s wildlife and ecosystems,” said Sheri S. Mann, Kaua‘i branch manager of the state Department of Land and Natural Resources Division of Forestry and Wildlife.

Rabbits were eradicated from the state sanctuary for seabirds in 2006. But getting rid of the rats proved more difficult.

The DLNR, Island Conservation, state Department of Agriculture, U.S. Fish and Wildlife Service, U.S. Department of Agriculture, U.S. Coast Guard, and the owners of Ni‘ihau joined forces in 2017 to implement a rat-eradication operation on Lehua, using lessons learned from a failed attempt in 2009.

That 2017 effort included dropping a rodenticide from helicopters over Lehua Islet, and a years-long mop-up effort to destroy any rats not affected by the rodenticide.

“Mahalo to DLNR’s Division of Forestry and Wildlife and all the partners involved for their efforts to eradicate the invasive species on Lehua Island,” said Kaua‘i Mayor Derek Kawakami.

“This great work ensures that Hawai‘i’s seabird sanctuary can once again safely host our native seabirds that are so crucial to the ecosystem and our local fisheries.”

Mele Khalsa of the nonprofit Island Conservation, technical advisor on the eradication, said: “The operation went really well, and almost immediately we saw signs of recovery across the island. But in the months that followed, cameras captured an unexpected outcome — a small number of rats were still present on the island.”

A response team was deployed, and a robust monitoring effort using motion-sensor cameras to detect rat presence or absence was initiated. The team regularly returned to Lehua to treat small areas with bait, and to set traps in response to any rat sightings.

Dr. Patty Baiao of Island Conservation explained: “We have collected robust data on the rat activity on Lehua since the eradication operation in 2017. With the success of the mop-up effort, rats have not been detected on the island for over twoyears.”

April 2021 marks the one-year anniversary since all rat-control treatments were removed from the island, adding to the data that allows experts to declare Lehua rat-free.

A February field trip to Lehua included a blessing by kumu Sabra Kauka, a well-known native Hawaiian educator.

“It was such a great honor to do a blessing, to see this place, the birds, and the people who’ve made this wonderful project an amazing success,” Kauka said. “Oh, my goodness! I can’t wait to tell my students about the absence of the four-legged rodents.”

Getting rid of the rats enables new possibilities for the birds of Lehua, which supports one of the largest and most-diverse seabird colonies in the main Hawaiian islands. At least 17 seabird species, many of which are threatened, call Lehua home.

During prime summer nesting season, hundreds of thousands of birds may be on Lehua at any given time. In the winter, red-footed boobies and Laysan albatross are among the dominant birds on the island.

The partners hope that Lehua might host the endangered Newell’s shearwater, which has been found attempting to nest on the island but was unsuccessful due to rat predation.

Restoring some of the 14 native plants, 11 of which are found only in Hawai‘i, is the next step in the project.

The National Tropical Botanical Garden is a key partner for plant-restoration efforts, as it was after the 2006 rabbit eradication. Mike DeMotta, a NTGB botanist, is looking forward to seeing Lehua completely restored post-rats.

The removal of these invasive species is an incredible milestone for the recovery of Lehua Island, DeMotta noted: “If you restore the ecosystem, the birds will come.

“The birds have been coming there long before men were on these islands. It’s an ahupua‘a system,” DeMotta said.

“Restoring the ecosystem generally will not only be a benefit to the birds, but also any other organisms that are native there. There are probably dozens of undescribed Hawaiian micro moths and other things that are occurring that will really benefit from ecosystem restoration,” he said.

”So, I think a holistic view of restoring the ahupua‘a on Lehua is really an important thing to keep in mind.”

The partners are eager to see how the island ecosystem recovers over the next few years, with plans to follow up in the near future with more marine monitoring to compare to the baseline from before the eradication to detect any changes in near-shore waters as a result of the vegetation and species occupation on the island.

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Jessica Else, editor, can be reached at 245-0457 or jelse@thegardenisland.com.