History and current status of invasive nutria and common muskrat in Korea.
Nutria, or coypu (Myocastor coypus), were introduced to South Korea in 1985 and became an invasive species in the late 1990s. Despite being limited to the Nacdong River system, the nutria population is well established there. The common muskrat (Ondatra zibethicus) invaded North Korea via the Russian and Chinese borders during the 1960s, but the species is still confined to the extreme northeastern portion. In South Korea, muskrats were introduced in 2005. Although muskrat farms are not commercially viable, they have increased. Since 2009, local and federal governments have tried to remove nutria using trappers and bounty hunting. From 2011 to 2015, 11,258 nutrias were removed but a sustainable population still exists. Although complete nutria removal has been achieved in other countries, the eradication campaign in South Korea has not been strictly modeled on these successes. Despite the concern about muskrats, prevention against their possible release has never been implemented. We present the history of nutria and muskrat in Korea and examine the current eradication projects. We propose that unified science-based eradication strategies would be the most likely to succeed, and urge the South Korean government to initiate management designed to avert potentially harmful ecosystem effects of invasive muskrats.