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Encouraging Signs from Lehua Island Show No Rats

Aerial photographs of Lehua, rats, birds, and rodenticide application. PC: Hawai‘i DLNR.

Monitoring efforts of the ecosystem recovery on Lehua Island find no signs of invasive Pacific Rats in the four months following a rat eradication effort, according to the state Department of Land and Natural Resources.

Though Lehua Island Restoration Project partners won’t declare the eradication effort a complete success until next September, monitoring teams say they are encouraged by the observations so far.

The restoration project is not just aimed at protecting and increasing seabird populations, but it is intended to create a “habitat-level transformation.” For decades, rats have attacked native seabirds on Lehua, eating their eggs and chicks.  Rats also devoured the seeds and leaves of many of the native plants that support other life on Lehua Island. Planting of endemic species of plants is expected to start next year.

“While we conducted our monitoring work we’d been looking for any sign of rat predation and rats. So far, we’ve seen no signs of rats anywhere on the island, which is a stark difference from trips before the rat eradication work began,” commented Dr. Andre Raine of the Kaua‘i Endangered Seabird Recovery Project. His team spent two days last week surveying an albatross colony on the steep cliffs of the north side of the island. Raine explains they did a thorough survey of the entire area, counting nesting Laysan and Black-footed Albatrosses and pinpointing each nests location with GPS. “This year we have lots of albatross out here which is great; about 145,” Raine said.

This is the second monitoring trip by the KESRP team since the last of three aerial applications of rodenticide in September. Raine and other scientists from Island Conservation and DLNR who have conducted separate excursions all report no signs of rats.

In late September, the KESRP team recorded a Bulwer’s petrel chick on a game camera exercising outside its burrow. Dr. Raine explains, “This is the first time we have ever seen this on Lehua, as this species is a favored prey of the rats. The chick had this crazy little “hair-do” of down on his head, which was waving about in the wind; it was really cute. If the rats are truly gone we should see this happening more and more – the tiny ground-nesting seabirds in particular should really start increasing in numbers.”

The restoration team points to similar projects, like the burgeoning albatross colony at Oʻahu’s Kaʻena Point Natural Area Reserve, as a shining example of how seabird populations can recover when protected from predators like rats. At Kaʻena Point a predator-proof fence also keeps cats and other predators away from albatross and other bird species.

Raine concluded, “If the rats are gone, we should see a lot more seabirds out here – populations increasing rapidly as more and more chicks fledge instead of being eaten by rats. Lehua can hold a hell of a lot more birds than are currently here. So we’d expect to see huge increases in population sizes and hopefully new species appearing. The future is looking bright for the island and its native seabirds.”