Predator-proof fencing as a management tool in the Hawaiian Islands: protecting Laysan Albatrosses within the Kaena Point Natural Area Reserve

Lindsay Young (Pacific Rim Conservation, Honolulu, Oahu, Hawaii) and colleagues have produced a technical report that details the success of the predator-proof fence at Kaena Point on the Hawaiian island of Oahu which is allowing ACAP-listed Laysan Albatrosses Phoebastria immutabilis and Wedge-tailed Shearwaters Puffinus pacificus to breed in the absence of introduced predators.

The report’s abstract follows:

“The Ka`ena Point Ecosystem Restoration Project was the result of a partnership between the Hawai`i Department of Land and Natural Resources, Divisions of Forestry and Wildlife and State Parks, the U.S. Fish and Wildlife Service, and the Hawai`i Chapter of The Wildlife Society. Ka`ena Point Natural Area Reserve (NAR) hosts one of the largest seabird colonies in the main Hawaiian islands, three species of endangered plants, and is a pupping ground for the endangered Hawaiian monk seals. Prior to fence construction, nesting seabirds and native plants were under constant threat from predatory animals; up to 15% of seabird chicks were killed each year prior to fledging and many endangered plants were unable to reproduce as a result of seed predation. The project involved the construction of predator-proof fencing (2m tall) to prevent feral predators such as dogs, cats, mongoose, rats and mice from entering into 20ha of coastal habitat within Ka`ena Point, followed by removal of these species. The project was initiated with the hiring of a project coordinator, followed closely by hiring of a two-person public outreach team. The public outreach was extensive reaching over 2500 individuals via personal contact and tens of thousands more as a result of dozens of stories appearing on evening news channels, articles published in local newspapers and newsletters, and several mini-documentaries aired on local cable television shows. A website was also established to post educational materials and information on the project (www.restoreKa` The vast majority of the public was supportive despite the vigorous objections of a few individuals. Multiple federal, state and county permits were required. In total 12 permits were applied for and obtained over a four-year period. Two years were lost as a result of multiple contested cases filed against the project which prevented progress during their resolution. Final permit approvals were completed in November 2010, construction began on November 10, 2010 and was completed on March 30, 2011 after a two-month hiatus for the holidays. To document the effects of predator removal, extensive ecological monitoring was conducted on both native and non-native species prior to the predator removal. A permanent monitoring grid with points placed every 50 m was established in the reserve to document micro-habitat shifts. Seabird populations in the reserve had been monitored intensively for over seven years, and a complete botanical, invertebrate and marine intertidal survey was conducted to document the vascular plant species present and their percent cover. Extensive rodent monitoring was also conducted to document the species present, their relative abundance, reproductive cycle, and home range to select the most effective eradication method. Based on monitoring results and regulatory restrictions, a combination of diphacinone in bait boxes, as well as live traps were used to eradicate rodents, and a combination of live-trapping and shooting was used to remove larger animals such as dogs, cats and mongoose. Invasive mammal eradication operations were initiated in February 2011 during the low point in the rodent reproductive cycle, using a combination of rodenticide in bait boxes spaced 25 m apart and live multiple-catch traps placed 12.5 m apart. Within three months, all predators, with the exception of mice were eradicated from within the reserve. Mice took an additional six months to full remove and operations were completed in the fall of 2011. The exclusion and removal of these predatory animals is anticipated to increase in the existing population of nesting seabirds, encourage new seabird species to nest at Ka`ena Point, enhance regeneration and recruitment of native plants, and benefit monk seals by reducing the risk of disease transmission. The Ka`ena Point Ecosystem Restoration Project is expected to have primarily positive effects on the resources protected in the NAR and provide the people of Hawai`i with an opportunity to visit a restored ecosystem. This was the first predator proof fence constructed in the United States at the time of its completion, and was the first project to successfully eliminate mice using the techniques discussed above.”

One of the three self-closing gates in the Kaena Point predator-proof fence

Photograph by John Cooper


Young, L.C., VanderWerf, E.A., Mitchell, C., Yuen, E., Miller, C.J., Smith, D.G. & Swenson, C. 2012. The use of Predator Proof Fencing as a Management Tool in the Hawaiian Islands: a Case Study of Ka`ena Point Natural Area Reserve. Technical Report No. 180. Honolulu: The Hawai`i-Pacific Islands Cooperative Ecosystem Studies Unit & Pacific Cooperative Studies Unit, University of Hawai`i. 82 pp.

John Cooper, ACAP Information Officer, 28 March 2013

The Agreement on the
Conservation of Albatrosses and Petrels

ACAP is a multilateral agreement which seeks to conserve listed albatrosses, petrels and shearwaters by coordinating international activity to mitigate known threats to their populations.

About ACAP

ACAP Secretariat

119 Macquarie St
Hobart TAS 7000

Tel: +61 3 6165 6674