Shun Takagi

There is an urgent need to develop global observation networks to quantify biodiversity trends for evaluating achievements of targets of Kunming-Montreal Global Biodiversity Framework. Camera traps are a commonly used tool, with the potential to enhance global observation networks for monitoring wildlife population trends and has the capacity to constitute global observation networks by applying a unified sampling protocol. The Snapshot protocol is simple and easy for camera trapping which is applied in North America and Europe. However, there is no regional camera-trap network with the Snapshot protocol in Asia. We present the first dataset from a collaborative camera-trap survey using the Snapshot protocol in Japan conducted in 2023. We collected data at 90 locations across nine arrays for a total of 6162 trap-nights of survey effort. The total number of sequences with mammals and birds was 7967, including 20 mammal species and 23 avian species. Apart from humans, wild boar, sika deer and rodents were the most commonly observed taxa on the camera traps, covering 57.9% of all the animal individuals. We provide the dataset with a standard format of Wildlife Insights, but also with Camtrap DP 1.0 format. Our dataset can be used for a part of the global dataset for comparing relative abundances of wildlife and for a baseline of wildlife population trends in Japan. It can also used for training machine-learning models for automatic species identifications.

<p>We recorded a Japanese marten biting the neck of a wild boar piglet, using an infrared-triggered camera installed in the forest in Gifu Prefecture, Japan. It is unclear whether Japanese martens actively capture wild boar piglets as a food resource, but we propose that Japanese marten as a potential predator of wild boar piglets.</p>

<p> Recently, the floating-leaved plants, especially Trapa spp., have been increased in many shallow and eutrophic lakes in Japan. In this study, we investigated the seasonal changes in water qualities in relation to the presence / absence of Trapa natans in the eutrophic Lake Inba. In the Trapa growing seasons (from July to September), the percentage of dissolved oxygen and turbidity were lower in the Trapa beds than the open water without Trapa. Dissolved oxygen significantly decreased near the bottom especially at night. Turbidity was significantly lower both at the surface and bottom layer in the Trapa beds only in the Trapa growing seasons. Low oxygen and turbidity in the beds might be due to the reduced water currents and the suppression of photosynthesis by phytoplankton under the low light conditions. There were no significant differences in nutrient concentrations between Trapa beds and the open water, though high concentrations of NH₄-N in the Trapa beds were observed in August and September. Decay and decomposition of Trapa and anoxic condition near the sediment might have caused the release of inorganic nitrogen into water. While in the non-growing seasons, there were no significant differences on water qualities between the stations. Differences in water qualities were more remarkable between seasons that total phosphorus concentration was high from July to September, while NO₃-N and NO₂-N were high in other months. Since those seasonal changes in nutrient concentrations were common in Lake Inba, the effects of Trapa spp. on nutrient concentrations were much smaller than the other factors affecting seasonal variations.</p>

<p>We investigated the spatial distribution of macrobenthos in salt marshes along the coast of Tokyo Bay, with environmental factors that influence their distribution. The field survey was conducted at 31 sites along the entire coast of the bay, in which presence or absence of the salt marsh animals and environmental factors (salinity, ORP, median grain size, elevation, vegetation area) of the habitats were examined. Most of common species of mollusks and crustaceans were distributed on entire coast of the bay, but some of endangered species showed restricted distribution in the coast. The restricted distribution of endangered salt marsh crabs were explained by several environmental factors; higher salinity and lower elevation of the habitat were suitable for Helicana japonica and Parasesarma affines, which were distributed in eastern coast in the bay, and Sesarmops intermedium, that was distributed in western coast and inner part, tended to inhabit higher elevation sites. Since local populations of these salt marsh species in the bay may be consisted of bay scale metapopulation that are formed by connectivity between small local populations through larval dispersal, distributional restriction of the salt marsh crabs in the bay may indicate that these endangered species are regarded as being difficult to persist in the bay. New local populations of the salt marsh benthos animals could be restored by creation of salt marsh habitats along the bay, to increase of the connectivity between local populations in the bay.</p>