Izu Ōshima
In the 1960s, several specimens escaped from an exhibition zoo in the Bōsō Peninsula in eastern Japan. By 2017, their numbers had reached at least 60,000. It is considered a harmful invasive species and has inflicted severe damage to ashitaba plantations. Also, Reeves's muntjac escaped a zoo on Izu Ōshima in 1970 when a fence fell due to a typhoon. A muntjac eradication effort on Izu Ōshima was undertaken in 2007–2014 but failed, and as of 2014, at least 11,000 individuals exist and have a yearly population growth rate of 15%. This failure has been blamed on inadequate survey methods that underestimated the population of the nocturnal species.