Utilization of municipality records for the early-stage management of introduced raccoons in Japan

Rapid response is critical for management of invasive alien species (IAS). However, lack of ecological information at early stages of invasion is a challenge for development of management strategies. To facilitate development of an IAS management strategy, we investigated the stages of invasion and habitat preferences of raccoons (Procyon lotor) believed to be in the early stage of invasion at Tokachi, Hokkaido, Japan. We obtained raccoon records from local municipalities in Tokachi including trapping and individual biological data (2006-2014), necropsies conducted on 161 carcasses collected as roadkill or by traps (2009-2014), and track surveys (August-November, 2010). Female raccoon reproductive statuses indicated populations are established and actively breeding in Tokachi. Relative population densities (based on catch per unit effort) and annual changes in raccoon capture sites revealed raccoon expansions, which were likely localized to the western region, indicating district-level variation in invasion stages. The distribution of livestock farms may have positively influenced raccoon occurrence and body sizes. Half of sampled raccoons had recently eaten corn (Zea maize), presumably obtained from livestock feed. Therefore, livestock farms may represent preferred raccoon habitats and could facilitate raccoon establishment. In Tokachi, IAS management strategies (i.e., prevention, eradication, and impact mitigation) should be tailored to stage of invasion at the local level. In particular, increased monitoring and capture efforts in areas with many livestock farms might retard raccoon establishment. More broadly, at early stages of invasion, IAS data from local municipalities may facilitate development of management strategies.