Creating an island free of predators

LIHUE — Researchers reported a successful result from this week’s bait experiment to eliminate the rat population on Lehua Rock.

State, federal and non-profit partners used a helicopter to drop onto the island non-lethal, non-toxic bait, a tactic they hope will ultimately lead to the use of lethal rodent bait to eliminate Lehua’s rats.

Invasive rats are the primary predator of endangered seabirds that could otherwise establish breeding colonies on the small island, located 17 miles west of Kauai, just off the northern tip of Niihau.

“On Lehua, we have the opportunity to create the largest predator-free habitat for threatened and endangered seabirds anywhere in Hawaii,” said Alex Wegmann, Hawaii Program manager for the non-profit Island Conservation, which is leading the project. “Lehua is roughly 360 acres and when it becomes predator free it can serve as critical breeding and nesting habitat for the three endangered seabird species, as well as for others.”

Newell’s shearwaters, Hawaiian petrel and the Band-rumped storm petrel may have been nesting there prior to the introduction of rats and rabbits.

Rabbits have already been eradicated from the island.

“This was a trial run; a chance to fly a helicopter over Lehua and drop non-toxic bait onto the island,” said Joshua Atwood, invasive species coordinator for the state Department of Land and Natural Resources. “This is the same formulation we’d use in a rodent-control project, except it didn’t have rodenticide in the mix at all. This will give us a better understanding of where rodents are on Lehua and now they interact with the food web and threaten the endangered birds.”

The results of the aerial drop project will provide guidance for the potential development of a new project to use a rodenticide to control Lehua’s invasive rat population. The project would be at least one year out.

MJ Mazurek, Island Conservation’s Hawaii Program project manager, said the next step is to set up bait availability plots, where researchers look at the availability of bait over a specific period of time.

“The way a rodenticide works, is you need to have a series of feedings and have the bait available for that time period, so that the toxicant can do its job,” Mazurek said.

In addition to DLNR and Island Conservation other project and funding partners include the U.S. Fish and Wildlife Service, National Tropical Botanical Gardens, National Fish and Wildlife Foundation, Bell Laboratories and the David and Lucile Packard Foundation.

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