Back to Life When Rats are Gone, Birds and Plants Thrive
By Hob Osterlund, Safina Center Fellow
An interview with Mele Khalsa, Island Restoration Specialist, Island Conservation.
Lehua. Photo: Island Conservation
It's been nearly two years since Island Conservation coordinated the rodenticide drop on Lehua Island, about nineteen miles off the west coast of Kaua'i. Have you detected rats there since then?
There has been sporadic evidence of rats on the island in very low densities. The first one was seen on a motion-triggered monitoring camera in December, 2017 and that detection was quickly followed up with trapping and localized treatment. Sightings continued at a rate of approximately one rat every other month and we continued follow-up and trapping for each sighting thereafter. The most recent rat was detected in December, 2018. Since then we have seen some rat poop in the bait stations. Fortunately, there’s no evidence of a growing population, which we would have expected to see by now. Under the right conditions, two rats can become fifteen thousand rats in one year (bolding mine.) It’s been almost two years of intensive island-wide monitoring and we’re just not seeing those kinds of numbers. This gives us hope that rats can still be completely removed from Lehua in the near future.
How are the nesting seabird counts this year compared to 2017?
We are seeing a significant increase in native seabirds with the reduction of invasive rats. The most significant increases in nesting success have been with the smallest nesting seabirds—the Bulwer’s Petrels, for example. We only have one full year of seabird nesting data post-eradication so it’s hard to see a trend just yet but at the end of 2019 we should have a better picture of the seabird response overall. Based on my experiences on Lehua, I can say that before the eradication there were rat-predated chicks and eggs everywhere. I’m happy to report that I haven’t seen a single predation since 2017.
That’s such good news. Tell us about how you used dogs to help find any remaining rats.
We have done surveys with trained detection dogs on Lehua twice since implementation. We use the dogs to survey large areas of the island for rat signs that might be missed by our other monitoring efforts. The dogs can be a useful tool, but their use on Lehua is limited because of the potential negative effects they can have on nesting seabirds. Even though the dogs are trained not to go after birds, birds can be flushed off their nests during dog surveys. Because of this, we only use dogs December-March each year when burrow-nesting seabirds are absent from Lehua.
What impact has the rat reduction had on native vegetation?
In June 2016 the vegetation was almost nonexistent except for a few shrubs by the summit. In June 2018 there were grasses, groundcovers, and small shrubs popping up everywhere. A vegetation restoration plan to enhance seabird nesting habitat is being developed. We would also like to get more native shrubs established. The native plants already there are now able to set seed without getting chewed apart by invasive rats. We have not observed any rat predation on native plants since implementation in 2017 and that is very exciting!
What are the roles of various agencies on the mop-up phase of Lehua Island Ecosystem Restoration Project?
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.
Mice on Midway Atoll are predating on nesting albatross there. Tell us about the plan for mouse eradication planned for 2020.
The Midway project plan is still in development, but the Final Environmental Assessment and Finding of No Significant Impact (FONSI) are published here.
Although potentially more challenging, mouse eradications utilizing broadcast of rodenticides have been successful in several tropical islands similar to Midway.
Here on Kaua'i there was considerable pushback against the rodenticide drop in 2017. Many community objections were based on rumors rather than scientific or historic facts. Given your experience, how would you advise another conservation agency preparing to take action that might be at similar risk for being misunderstood?
Our approach was to transparently communicate the benefits and potential risks of the conservation intervention. A key aspect is to identify key stakeholders, engage with them early on in the planning process, and provide ample opportunities for information sharing and discussion. I would also suggest building a supportive base of people within the community who can help share accurate information through their own connections. In a small community like Kauai it’s easy to reach a lot of people this way.