Mammal Study

Crop damage caused by mammals is not uniformly distributed and is more localized near the forest; this damage distribution differs from that of insect pests. Species that cause damage are often forest inhabitants and hence the damage sites are also biased toward the forest edge. However, these species do not necessarily use forests as their home ranges for cover or shelter, but may be entirely urban (e.g., urban bears). Forest vegetation cannot be considered essential for these species, as this contradicts the behavior of animals that use urbanized areas only. Our review illustrates why crop damage is uneven, localized at forest edges, and less likely to occur on farmlands away from forests in terms of population density, food availability, personality, habituation, and human behavior. This review reveals the role and risk perception of human disturbances. If risk of farmland is perceived to be greater than the true risk, mammals prefer farmlands near forests with low degrees of human disturbances (perceptual trap). The current damage distribution is a result of this perceptual trap because hunting pressures are not always higher in farmlands than in forests.

To obtain proper estimates of wildlife abundance by harvest-based models (HBMs), an understanding of the model structure and data properties is required. Otherwise, there may be a risk of failure to obtaining adequate estimates. In this study, we estimated the abundance of sika deer using several spatially fine-scale HBMs with different structures and aimed to clarify the effects of the model structure and data quality on estimates. We used monitoring data collected by the Gifu Prefectural Government and other data collected by the authors. Four HBMs were constructed according to the combinations of the model structure (considering overdispersion in the observation models) and data (with or without additional observation data), and their parameters were estimated. The results showed that among the four HBMs, reasonable deer abundance was estimated by two HBMs in which overdispersion was considered in the observation models of the less precision data only. As the parameters failed to converge in the other two HBMs in which overdispersion was considered in all observation models, the abundance would be overestimated. Thus, our results confirmed that understanding the model structure and data properties was essential for obtaining proper estimates of wildlife abundance from currently available data with HBM.

（要旨）．ニホンジカ個体数推定のためのHarvest-based modelsにおける適切なモデル設計の検討．Harvest-based models（HBMs）を用いて野生動物の適切な個体数推定値を得るためには，モデルの構造とデータの特性を理解することが必要である．これらに対する理解が不十分な場合，適切な推定値を得られないリスクが大きくなる．本研究では，狩猟メッシュを単位とした空間解像度の高いHBMsを複数構築してニホンジカ個体数の推定を試み，モデル構造とデータの質が個体数推定値に及ぼす影響を明らかにすることを目指した．データとして，岐阜県が収集したモニタリングデータと，筆者らが収集した観測データを用いた．モデル構造（観測モデルにおける過分散の考慮の有無）とデータ（追加観測データの有無）の組み合わせにより，4つのHBMsを構築し個体数推定を試みた．その結果，4つのモデルのうち，精度の低いデータに対する観測モデルのみに過分散を設定した2つのモデルでは妥当なニホンジカ個体数が推定された．一方，すべての観測モデルで過分散を考慮した他の2つのモデルではパラメータは収束せず，また個体数推定値は過大であった．本研究の結果から，ある時点で利用可能なデータからHBMsを用いて野生動物の個体数を適切に推定するためには，モデル構造とデータの特性に対する理解が不可欠であることが確認された．

Agricultural damage caused by wild Japanese monkeys (Macaca fuscata) has become a serious problem in Japan. Residents have tried to protect their crop fields from monkey invasions, but the excellent physical and learning abilities of the monkeys have made the protection difficult. At present, many local governments are attempting to reduce the damage mainly through culling, but unplanned population management often results in over-culling, which consequently leads to local extinction. Here, I introduce a case study in Kami Town, Hyogo Prefecture, western Japan, in which the local government simultaneously implemented three countermeasures: 1) organizing a monkey patrol group, 2) expanding inexpensive and easy-to-use electric fences, and 3) selective capturing of problem animals. After the implementation of these countermeasures, frequency of chasing away the monkeys around crop field (a total of 319 times in 2010 compared to less than 100 times in 2017) and amount of agricultural damage (2011: 2 925 000 JPY, 2017: 876 000 JPY) decreased. These results showed that in order to decrease agricultural damage while maintaining a stable monkey population, a combination of multiple countermeasures is a good solution, and methods applied in Kami Town should also be implemented in other areas where monkeys regularly damage crops.

Large carnivores utilize human areas, resulting in frequent conflict with humans. We aimed to identify the factors affecting the habitat use of leopards and sloth bears in human-dominated areas of the proposed Jawai Leopard Community Conservation Reserve, Rajasthan, western India. Within the 1 km² grid framework, the presence of species was recorded (84 events - leopards and 71- sloth bears) and modeled using the maximum entropy algorithm concerning terrain and land-use pattern-related covariates. Also, we modeled the potential movement areas using the least-cost pathway approach. Outcomes informed that suitable habitats for leopards (126.1 km²; 40.8% of study area) were more widely distributed than sloth bears (103.7 km²; 33.5%). Models suggested that elevated-rugged hillocks were positively related to both species' habitat use, followed by scrub and water resources. Leopards showed more adaptability towards human settlements than sloth bears. Thirty potential movement pathways (between 15 core habitats) for leopards and 19 for sloth bears (between 11 core habitat nodes) were identified; out of these, 45% and 48% of pathways for leopards and sloth bears, respectively, are facing threats by the movement barriers such as railway tracks and human settlements. Conserving highly and moderately centralized pathways can be a better approach for sustainable landscape conservation in parallel.

The small Japanese field mouse Apodemus argenteus is known to disperse the highly toxic seeds of the Japanese star anise Illicium anisatum (Schisandraceae); however, whether the large Japanese field mouse A. speciosus does so remains unexplored. Seeds of I. anisatum were placed in mesh cages with openings sized only for small rodents and monitored at two forest sites in Tsukuba, Ibaraki Prefecture, Japan, in autumn 2018. Any animals approaching or entering the cages were recorded by automated cameras with infrared motion sensors. Only A. speciosus was recorded entering the cages. At both sites, some seeds were consumed inside the cages or transported outside them. These results show that A. speciosus interacts with seeds of I. anisatum and is a potential agent of seed dispersal. Further study is needed to determine whether it can tolerate anisatin, the main neurotoxin in I. anisatum, and the possible tolerance mechanism.

The Ryukyu long-furred rat Diplothrix legata is endemic to the central Ryukyus and is the largest arboreal murid in Japan. This species is listed as ‘Endangered’ in the IUCN Red List. Invasive mammalian carnivores have been recorded as predators of this species; however, information on native predators is limited. We observed a juvenile Ryukyu long-furred rat caught by a jungle crow Corvus macrorhynchos connectens in a nesting tree cavity. Our observations suggest that jungle crows may be among the top predators in this area. On the same night on which the predation was observed, adult Ryukyu long-furred rats carried juveniles away from the tree cavity. It is possible that the adult individual left their nest and moved to other sites to avoid further predation.

Abstract in Japanese（要旨）． リュウキュウハシブトガラスによるケナガネズミの幼獣の捕食と巣の移動事例． ケナガネズミは中琉球の固有種で，日本で最大の樹上性ネズミ類であり，IUCN Red List で Endangered（EN） に指定されている．本種の捕食者としては，外来食肉目が記録されているが，在来捕食者の情報は少ない．我々 はケナガネズミの営巣樹洞において，リュウキュウハシブトガラスによるケナガネズミの幼獣の捕獲を記録 した．ハシブトガラスが本地域の生態系の中で，上位捕食者として位置する可能性が示唆された．また，同 日夜，ケナガネズミの成獣が残った幼獣を 1 頭ずつくわえて樹洞から出ていった．幼獣の捕食回避のために 巣の移動をした可能性がある