Coarse woody debris (CWD) is an important material for providing habitats for aquatic organisms. In this study, pieces of CWD of different sizes were artificially installed in a creek and their effects on the physical and biological environments were investigated. The flow velocity decreased and the water depth increased near the CWD. The streambed sediment was composed of sand in the upstream of the CWD and gravel in the downstream of the CWD. Fish were abundant near the CWD, and aquatic insects increased in number. It is postulated that the water flow changed due to the topographic alteration caused by the CWD, and that the CWD had some role in providing habitats for various aquatic organisms, resulting in their increased abundance. The effects did not significantly vary depending on the size of CWD, and even a small piece of CWD had a significant effect.

View full abstract

The shape of acorns of the Fagaceae family varies under influence of environmental, distributional, and genetic factors. Multiple studies have been conducted on acorns from forests; however, many trees of the Fagaceae species are also found at parks and along streets in urban areas. Since urban environments are different from those of forests, there may be differences in the factors that affect the shape of the acorns. Thus far, there have been very few studies on the shape characteristics of acorns in urban areas. In this study, acorns were collected from Quercus serrata and Lithocarpus edulis trees at eight urban sites and compared in four characteristics: length, diameter, L/D ratio, and volume. The results showed differences in the shape of acorns among the cities and among the sites within the individual cities.

View full abstract

The diet of introduced raccoon dogs (Nyctereutes procyonoides albus) was examined by fecal analysis in early autumn on Okushiri Island, Hokkaido. A total of 39 feces were collected from 37 latrines in September 2021 and analyzed using the point frame method. The most common foods of raccoon dogs were insects (frequency 100%; mean occupancy 47.1%) and fruits (frequency 87.2%; mean occupancy 30.8%). The insects were mainly Coleoptera (frequency 100%; mean occupancy 35.2%), of which the occupancy was higher in this study than previously reported from other regions. High predation pressure of the alien raccoon dog might have a negative impact on insect communities.

View full abstract

Cipangopaludina chinensis laeta (Martens, 1861) is listed as an endangered subspecies in the Red Data Books of Japan and Tokyo. There are no reliable records of this subspecies from Tama, a region of Tokyo, since 1985. This study reports the subspecies found to be surviving specimens in earth ditches (branches of the Honjuku Canal) passing through paddy fields in Fuchu City, Tama, in August 2013 and 2014. Further studies are necessary to elucidate the distribution and genetic characteristics of this subspecies throughout the region for implementing conservation measures.

View full abstract