Endemic Amami Jay, invasive Small Indian Mongoose, and other alien organisms: a new century investigation of island aliens towards improved ecosystem management

Abstract

The Amami Islands in southern Japan host many endemic species, including Amami Jay (Garrulus lidthi). Following the introduction of Small Indian Mongoose (Herpestes auropunctatus) in 1979, populations of Amami Rabbit (Pentalagus furnessi), Amami Woodcock (Scolopax mira), Amami Ishikawa’s Frog (Odorrana splendida), and other endemic species declined in the 1990s, as the mongoose expanded its population. A mongoose control project since 2000 successfully reduced the mongoose population to a very low density by 2014, resulting in the initial recovery of severely affected animal populations. Amami Jay was removed from Japan’s endangered species list in 2008. However the population and range of Amami Jay are still small (ca. 700 pairs, sometimes with other family member(s), in 700 km2), and other invasive species, such as cats and black rats, continue to damage the native ecosystem. Additionally there is a constant threat of new invasions to the Amami Islands. Our research shows that Amami Jay breeding success depends on the dominant oak (Castanopsis sieboldii) acorn production as much as predation. Therefore conservation plans should consider both short- and long-term effects and potential interaction by both invasive species and other natural factors. Understanding the Amami Jay population dynamics and sustainability from the multiple view points of, such as, population ecology, disease ecology, genetics, and also with ex situ conservation efforts as they relate to invasive species demands, will sophisticate our ecosystem research and management. We discuss how this endeavor of ours might develop as a model activity for maintaining biodiversity under threat from multiple invasive species.