環境

In order to clarify the inhabitation status of the non-native raccoon (Procyon lotor) and mid-sized mammals in the middle stretches of the Tamagawa-josui Aqueduct (18km in length), a search for traces of raccoons was conducted in the waterways from February 2012 until March 2013, and a habitat verification study was performed using bait traps targeting raccoons and auto imaging devices. Also, regarding the capture of and damages by raccoons, Japanese raccoon dogs (Nyctereutes procyonoides) and masked palm civets (Paguma larvata), interviews of all municipalities excluding the islands in Tokyo were conducted. Furthermore, eye-witness information was gathered from residents and the distribution of raccoons, raccoon dogs, and masked palm civets in Tokyo was made clear.

The auto imaging devices photographed raccoons in three locations in the waterways in the middle stretches of the Tamagawa-josui Aqueduct, making it clear that the waterway was being used by them. Traces were also identified in the vicinity of the locations where the raccoons were photographed, and the rate that the bait in the bait traps disappeared was high. From this, we believe there is a possibility that raccoons currently inhabit a limited area of the aqueduct basin. In addition, a large number of Japanese raccoon dogs and masked palm civets were verified in the tracking survey using sensor cameras, and there were locations where these species lived sympatrically with raccoons. The results of interviews of local authorities and reference documents show that there were 35 cities and towns that had raccoon sightings or habitat information. Habitat was verified in Kodaira City for the first time. According to the study, although the population density of raccoons in the mid-reaches of the Tamagawa-josui Aqueduct area is still low, the possibility of distribution increasing in the future is high, and it is suggested that early control measures, before damage occurs, is essential.

Hideo Wakazawa