LIHUE, KAUA’I – Monitoring teams are observing more albatross on Lehua Island than they have in a long time. There’s also no sign of rats consuming plants or seabird eggs, something that was commonplace a year ago. These are exactly the kind of early indicators project partners might hope to see – signs of a recovering island ecosystem, due to the removal of introduced, damaging (invasive) rats. But there is still work to do!
The Lehua Island Restoration Project Partnership is working hard to finish the ambitious operation initiated in 2017 to rid the island of predatory rats. Recently, remote, motion-activated monitoring camera ‘traps’ picked up three images of what are believed to be two or three rats on the steep and rocky cliff areas on the West and East sides of the island. Analysis of images show definitive proof of one rat; the other two are partial images that experts confidently believe to be rats.
For decades, invasive rats were having an ecosystem-wide impact on Lehua by consuming native plant seeds and preying on seabird chicks, eggs, and adults. In fall 2017, project partners applied a conservation bait to the island containing the rodenticide diphacinone to protect native species that depend on Lehua Island by removing invasive rats.
The project partners’ operational plans identified and explained that aerial application of rodenticide should result in complete eradication, and that on-the-ground spot treatments may be needed if rats are detected post aerial application. Spot treatments consist of hand placed traps and/or bait stations deployed in the areas with recent sightings. The bait stations are enclosed containers that permit rat access but prevent the low risk of exposure to non-target species like the islands nesting seabirds.
In their latest move to assist in removing the remaining rats, the Project Partners have recruited rat-detection dogs to join the team. The dogs will be deployed over the next two months. Similar, specially trained dogs have proven to be extremely successful in finding their targets as evidenced by their recent use to detect avian botulism at the Hanalei National Wildlife Refuge. Once the scent is identified, the handlers then help the dogs pinpoint the precise areas where rats are located. The dogs are trained and handled to minimize their interactions with native birds.
Since Lehua Island is relatively easy to access, the project team has been deploying an unprecedentedly high level of post-project monitoring. Every month since the rodenticide application last fall, a team from Island Conservation and DLNR’s Division of Forestry and Wildlife (DOFAW) and other partner organizations return to Lehua to monitor progress, retrieve photos from dozens of camera traps to search for rats, and to apply spot treatments and trapping aimed at eliminating any remaining rats. More remote projects often must wait a full year or two before more cost-prohibitive monitoring begins. Dr. Patty Baiao of Island Conversation explained, “Perhaps those hundreds of successful but more remote projects too had a few lingering rodents that, due to their inability to find each other and breed, naturally expired. Regardless, the project team is not taking any chances. We want nothing more than to document with scientific rigor the anecdotal seabird increases and benefits we have already begun to observe.”
Sheri S. Mann, Kaua‘i branch manager for the DOFAW commented, “A few rats remain. Of that we are certain, and the partnership is investigating why? In the meantime, we are implementing strategies designed for this scenario. We are committed to protect and enhance the seabird colonies on Lehua Island and will not rest until we have. As we double down our efforts using the best science, methods, and now specially trained dogs to achieve a complete eradication, our hope is only rivaled by our shared commitment.”