Rats Nearly Gone from Lehua Island

Good news from Lehua!  The state Department of Land and Natural Resources reports that the small island, just off the western coast of Kaua`i, has seen a near-total reduction in the rat population following three applications of a rodenticide.

Monitoring for rats on Lehua (DLNR photo)

Predation by rats on the resident seabirds has been dramatically reduced. Andre Raine, of the Kaua`i Endangered Seabird Recovery Project, one of the partners in the eradication effort, says the population of Bulwer’s petrels has benefited especially. “These small seabirds are easy prey for rats, and the fact that they are increasing is a great sign,” Raine said in a press release issued by the DLNR.

At the time the project was proposed, there were concerns that the rodenticide could harm fish. However, Sheri Mann, Kaua`i branch manager for the DLNR’s Division of Forestry and Wildlife, said there have been no observed negative impacts. “With increased survival of seabirds populating the island, the nutrients they bring to the island have benefits to Lehua from the top all the way to the ocean,” she said. “With the nutrients come more widespread and denser vegetation, which holds onto the soil and reduces runoff during rains. With reduced runoff comes healthier reefs and increased sealife.”

Since the most recent application of rodenticide – September 12, 2017 – no signs of rats eating eggs or chicks have been seen. Cameras have detected no rats since December 2018. However, what appeared to be rat fecal pellets were detected earlier this year, the DLNR press release stated, and monitoring for the presence of rats is continuing.

Suzanne Case, chair of the Board of Land and Natural Resources, says the ultimate goal “is the complete eradication of Pacific rats from Lehua.

“All our partners will continue to monitor the rat population and do spot treatments when and where they are seen…. With this continued effort, we are hopeful that the now extremely low rat population will eventually be eradicated.”

Although concerns had been raised prior to the initial application of the rodenticide that marine life could be harmed if the bait reached the nearshore environment, a report released last year by the U.S. Department of Agriculture “detected no rodenticide residues in samples of water, soil, `opihi, or seabirds, and minimal impacts to any species other than rodents,” the DLNR release states.

Environment Hawai`i published articles about the planned release of rodenticide in our April, July, and September editions in 2017.

— Patricia Tummons

One Response

  1. The State of Hawaii Division of Forestry and Wildlife is the lead on this project and they coordinate and staff our monitoring trips. Island Conservation continues to support the project with technical expertise in island restoration. The U.S. Fish and Wildlife Service is providing legal oversight of rodenticide use and technical expertise. The US Department of Agriculture provides support and technical expertise. The owners of Niihau remain very interested in seeing rats gone from Lehua once and for all and for the plant restoration work to get underway.

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