Moku‘auia is a 5-ha island off northeastern O‘ahu, Hawai‘i, that supports several thousand nesting Wedge-tailed Shearwaters (Puffinus pacificus) and several species of migratory shorebirds and is critical habitat for the federally endangered ‘ohai plant (Sesbania tomentosa). The island is separated from Mālaekahana State Recreation Area on O‘ahu by a channel 230 m wide and 1 m deep and receives numerous human visitors. Black rats (Rattus rattus) were first documented on Moku‘auia in 1967 and were eradicated in the 1990s, but rats recolonized the island and were eradicated again in 2006. We re-eradicated black rats in November 2011 following another recolonization, using snap traps and diphacinone in bait boxes spaced 25 m apart. Pre-eradication, 80% of tracking tunnels contained rat tracks. After 14 days, no more rats were trapped, bait take dropped to almost zero, and no rats have been detected since. Eradication of rats resulted in a doubling of Wedge-tailed Shearwater reproduction in 2006 and 2012 and is expected to enhance regeneration of native plants. Black rats may recolonize Moku‘auia periodically in the future because of its proximity to O‘ahu and the frequency of human visitation, but its small size and simple terrain make rats easy and inexpensive to eradicate, and the natural resources present warrant continued management.
Response of Wedge-tailed Shearwaters (Puffinus pacificus) to Eradication of Black Rats (Rattus rattus) from Moku‘auia Island after Reinvasion
