Present Status of Invasive Alien Raccoon and its Impact in Japan

Abstract

　Irresponsible breeding and release of pet raccoons (Procyon lotor) has caused their naturalization in Japan. The raccoons have already naturalized in 42 of Japan’s 47 prefectures, and there has been a remarkable increase in agricultural (cattle breeding) and urban areas, where the raccoons can find food and hide easily. Their home range size varies widely according to the habitat, ranging from 35 ha in urban areas to 2,219 ha in forests (mean: 299.1 ha). The raccoon avoids energy loss in winter by semi-hibernation. It has opportunistic and omnivorous feeding habits, taking crops and fruit in agricultural areas and native species in forests. It also preys on indigenous species such as the Japanese crayfish (Cambaroides japonicus) and Ezo salamander (Hynobius retardatus). Reproductive observations have shown high productivity (reproductive rate: 66% in yearlings and 96% in adults, litter size: 3.6 in yearlings and 3.9 in adults) and a potentially rapid rate of population growth (0.20 to 0.25). Intensive eradication guided by biological data will be indispensable to controlling invasive alien raccoons.