Impacts of Predation by the Invasive Black Rat Rattus rattus on the Bulwer's Petrel Bulweria bulwerii in the Bonin Islands, Japan
The black rat Rattus rattus is one of the most invasive alien species in the Bonin Islands and has been recorded on at least 16 of the islands. Higashijima, an uninhabited satellite island of Chichijima, provides breeding sites for thousands of Bulwer's petrels ( Bulweria bulwerii), and a massive die-off of this small petrel caused by rat predation was detected there in 2006. In total, 237 adult carcasses and 61 broken eggs were found in small plots totaling 0.035 ha in area during the year; this predation was estimated to have had devastating impacts on the population. Rat eradication was conducted in 2008, and although the petrel population was small, chicks were observed in 2009. The prompt eradication efforts during the early stages of rat predation prevented local extinction of the Bulwer's petrel. Broken eggs, a sign of rat predation, have also been found on other islands, and rats have been detected on most islands >2 ha in size. Eradication programs should be promoted on islands that currently support both small petrel populations and introduced rat populations before a crisis occurs.
KeywordsCamera Trap Common Buzzard Bonin Island Tooth Mark Intense Predation
We thank Naoko Suzuki, Harumi Horikoshi, Hayato Chiba, Yukiko Aoyama and trainees from Tokyo University of Marine Science and Technology for fi eld assistance. We would also like to thank Minoru & Yukari Masuda and Shobu Yamada for ship transport. Also to Takuma Hashimoto, Masaaki Takiguchi, Tatsuo Yabe, Naoki Kachi and Makoto Inaba whose productive discussion and information on the rat predation on Higashijima were always much appreciated. This study was supported by the Global Environment Research Fund of the Ministry of the Environment of Japan (F-051).
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