The Japanese mitten crab Eriocheir japonica is an edible species commonly inhabiting rivers throughout the Japanese Archipelago. The present study investigated daytime shelter preference of the crab by a field experiment. The riverine experiment was done in an enclosure that was screened with an agricultural plastic netting. The enclosure was composed of sixteen 1-m² sections, each section with one of the eight different riverbed substrate types (loose boulders with interstices, embedded boulders, loose cobbles with interstices, embedded cobbles, pebbles, sand, leaf litter, or woody debris; each with two replicates). Sixty-nine adult crabs were released into the enclosure and their hiding substrate types during the daytime were observed on a daily basis starting on the following day for 12 consecutive days. Of the total of 334 observations, 61.0% of the crabs were found in loose boulders with interstices, followed by woody debris (21.2%) and loose cobbles with interstices (12.8%). Significant positive rank correlations were observed between the carapace width of the crabs and the dimensions of the interstices used by these individuals (width: τ=0.232, height: τ=0.155, depth: τ=0.091), indicating that the preferred shelter size by E. japonica changes according to the body size.

Since 2005, Oriental white storks Ciconia boyciana have been continuously reintroduced by Hyogo Park of the Oriental White Stork (HPOWS) in the Toyooka Basin, Japan. However, most of them remain strongly dependent on hand-feeding in HPOWS after release because they can thereby obtain highly nutritious fish (Trachurus japonicus, Oncorhynchus mykiss, etc.). In contrast, a few storks are independent of hand-feeding, preying on various animal species (such as fish, frogs, insects, crustaceans) in the Toyooka Basin. However, this information on the foraging of reintroduced storks is on the basis of behavioural observations, but their trophic levels and food habits are unclear. Stable isotope analysis can be useful for estimating feeding habits. Therefore, we analysed carbon and nitrogen stable isotope ratios (δ¹³C and δ¹⁵N) in feeding-dependent storks (FDS) and -independent storks (IS), and then compared these values with those of captive-bred storks (CBS). The stable isotopic analysis showed that the levels of δ¹³C and δ¹⁵N were in the fol lowing order: CBS ＞ FDS ＞ IS. Our results suggest that the trophic level of storks rises upon strong dependence on hand-feeding; the provision of highly nutritious fish via hand-feeding thus has a major impact on the feeding habits of wild storks.

While it has been often reported that eco-friendly agricultures, such as using reduced amounts of agricultural chemicals and winter-flooded rice fields, have a positive effect on the restoration of paddy field ecosystem, as a practical matter, the prevalence of these agricultures is still being restricted regionally in Japan because of an increase in the cost of paddy field management as well as a decrease of crops. To widely improve paddy field biodiversity, establishment of restoration technologies that can be implemented easily and economically is essential. Here, we focused on swale as one of the restoration technologies. The swale is biotope-like waterside being created along the edge of paddy field to irrigate paddy water, and often provide a preferable habitat for a lot of aquatic organisms throughout a year. If installation of the swale into the most popular farming, i.e., conventional paddy field, became widespread, the paddy biodiversity may be improved efficiently and widely. To establish a procedure for introducing swale into conventional paddy fields, we verified the effects of two treatments on water quality and fish assembage in swale, i.e., sheeting on the bottom of swale for preventing water penetration and shortening swale size for reducing management cost. In the sheet treatment, there was no significant difference in water depth, water temperature, dissolved oxygen, number of fish species, fish abundance, and fish diversity between the swales with and without sheet, and no advantage could be recognized in this treatment. In the treatment varying swale size, no significant differences could be detected in all characteristics of water quality and fish assemblage among different-sized swales, which shows that even just small-sized swale provide an effective habitat for aquatic organisms. Thus the introduction of swale into conventional paddy fields may be an effective tactic capable of improving paddy field biodiversity easily without extraordinary management such as sheeting.

Artificial nests for raptors have often been constructed as environmental conservation measures in nationwide development projects. This study aimed to identify effective techniques for the setup and promotion of artificial nests for rare raptors through analysis of data from previous road projects. The data showed that 173 artificial nests were set up for 8 species of rare raptors in 31 road projects. These species included the goshawk (119 nests in 17 projects), hawk eagle (20 nests in 7 projects), buzzard (9 nests in 3 projects), osprey (4 nests in 3 projects), falcon (7 nests in 2 projects), grey-faced buzzard (7 nests in 2 projects), white-tailed sea eagle (5 nests in 1 project), and honey buzzard (2 nests in 1 project). Artificial nests were categorized into 6 types based on the materials used (natural or non-natural) and location of the nesting site (tree canopy, top of the tree, or other). The utilization rate after setup was the highest in cases of relocation or reuse of nest-building materials from old raptor nests. Nest height and positioning did not appear to affect utilization rates. However, the results suggest that the distance between artificial and former natural nesting sites is an important factor. In the case of the goshawk, the utilization rate of artificial nests increased when target pairs were relocated less than 250 m from their old nests. In addition, some non-target pairs (i.e., new pairs) began to breed in the artificial nests if the distance was greater than 1500 m. The results also showed that the time elapsed from setup of the artificial nests to utilization by target pairs was generally several years, and that adaptive managements may shorten this time. We suggest that these results support the use of artificial nests as raptor conservation measures in the future.

This study focused on 3 groups of rare plants that are recognized as being difficult to transplant, in order to develop conservation techniques for these plants. We categorized the groups (i.e., epiphytic, mixotrophic, and mycoheterotrophic plants) as difficult-to-transplant species, based on previous studies. We analyzed practical examples of transplantation in 179 road projects around the nation to examine the current status, issues, and best practices of transplantation, to provide insights into effective transplantation techniques. According to our results, all 26 species belonging to 8 families of the difficult-to-transplant plant groups were transplanted in road projects around the nation: 4 epiphytic species on a tree trunk, 6 epiphytic species in a rocky area, and 9 mixotrophic species and 7 mycoheterotrophic species. Epiphytic species in a rocky area showed the favorable survival rate after transplantation. The survival rates of both epiphytic species on a tree trunk and mixotrophic species differed greatly between species. Although the survival rate of mycoheterotrophic species could not be estimated, the scape was found in about 10 - 20 percent of transplantation cases. We also observed some effective transplantation techniques, such as the transplantation of epiphytic plants on tree trunks using wires and Sphagnum spp. in order to prevent detachment and drying, respectively, and the transplantation of mixotrophic and mycoheterotrophic plants with surrounding soil using a void tube or plastic basket in order to maintain symbiosis with mycorrhizal fungi. In addition, we did not find a example of transplantation using disseminules (e.g., seeds), although by this method, transplantation can be carried out without causing damage to the plant body. In future, it is important to gain knowledge of effective transplantation techniques and adopt the practice of transplantation using disseminules.

Rapid development and diffusion of unmanned aerial vehicles （UAVs） have been changing the natural environmental measurements in field survey and research. In this study, we attempted to validate the accuracy of natural-environmental measurements based on aerial photos from UAVs, and discussed the potential and problems in the use of UAVs. As a specific example, we took photographs of 1/70 “Gokase River” replication （width: approx. 10 m, length: approx. 95 m）, which was set up under open sky conditions, through a UAV at heights of 10 and 50 m, and conducted three-dimensional measurements based on the aerial photos using the structure from motion （SfM） technology. Digital surface models （DSMs） and ortho photos based on the UAV photos （number of pictures– 10-m shots: 126, 50-m shots: 24） were analyzed in the SfM using “Photoscan pro.” for each height. The accuracy was validated by comparing actual cross-sectional contours with predicted contours from the DSMs at four sites in river replication. The following results were obtained: 1） the predicted contours from DSM well captured the complex shape of the river replication, and 2） two predicted contours among four contours were especially accurate within 5 cm whereas other predicted contours near the margins of DSMs were susceptible to error （i.e., over 10-20 cm）. Thus, these results suggested that the combination of UAV and SfM facilitates efficient natural-environmental measurements.