嶌本 樹

Abstract Hair hormone analysis has received increasing attention in the fields of wildlife management and conservation over the last decade. However, few studies focused on sex steroid hormones, even though hair sex steroid hormone analysis has the potential to provide information on an individual's reproductive health, leading to a better understanding of animal reproductive biology and the assessment of individual and population health. Here, we tested the assay validation and examined whether hair progesterone concentration (HPC) differs between different sexes and age classes in the Asian black bear, Ursus thibetanus. We also investigated the effects of reproductive condition, age, and body condition index (BCI) on HPC to determine the utility of hair progesterone analysis in bears. The assay validation was reported in our study. We found a significantly higher HPC in adult females than in juvenile females and juvenile and adult males. In addition, we found no effects of age and BCI on HPC but a significant positive effect of reproductive condition, as the HPC in breeding adult females was significantly higher than in nonbreeding adult females. These results suggest that hair progesterone analysis has the potential to evaluate the reproductive condition of Asian black bears.

Abstract Human activities often induce maladaptive effects in urban wildlife, such as increased inbreeding and decreased gene flow, consequently leading to a loss of biodiversity. Although maladaptive effects are commonly reported in urban wildlife, some wildlife species are not affected. Understanding the conditions and factors that affect the genetic structure of wildlife is crucial for its conservation in urban environments. Eurasian red squirrels Sciurus vulgaris in Obihiro City, Hokkaido, Japan, have settled in large residential lots with a high risk of vehicle collisions for approximately 30 years, raising the possibility that the urban population would be genetically isolated from nearby rural populations and may experience a rapid decrease in genetic diversity. In this study, we analysed the population structure, genetic distance, and nucleotide diversity of squirrels in the Obihiro area using genome-wide single nucleotide polymorphisms (SNPs). Principal component analysis and ADMIXTURE showed that urban and rural squirrel populations formed distinct clusters with intermediate urban and rural boundary populations. Genetic distances between the urban populations were greater than that of other pairs. Nucleotide diversities were lower in urban populations than in other populations, suggesting limited gene flow between urban and other populations, possibly due to urbanisation. The change in the genetic characteristics of urban squirrel populations during this short period demonstrates the strong impact of urbanisation. Our findings suggest that a genome-wide approach to the genetic structure of wildlife contributes to its conservation in urban environments.

Abstract Urban environments are novel alternative habitats for wildlife. Anthropogenic food resources such as supplemental feeding (SF) are usually abundant, stable across seasons, and sometimes rich in calories. Although anthropogenic food resources could modify the seasonality and composition of the diets of urban animals, previous studies have been limited to qualitative assessments based on stomach content and food remains. Our study compared diet seasonality and niche width between rural and urban populations of Eurasian red squirrels (Sciurus vulgaris) in Hokkaido, Japan, using direct observation and stable isotope analysis. We found that dietary seasonality was lower in urban populations than in rural populations. The frequency of seed use was higher throughout the year in urban populations than in rural populations, possibly because of excessive seeds by SF in urban squirrels. Additionally, female body weights of the urban population were higher than those of the rural population. However, this was not true for males. Because high body weight can increase reproductive success in females, it is feasible that diet modification could contribute to population growth in urban squirrels. However, no differences in male body weight were observed, possibly due to energy loss caused by intense male–male competition at feeding sites. Our study highlights the importance of studying the multidimensional effects of anthropogenic foods on wildlife.

Abstract Scatter-hoarding animals decide their food hoarding location by assessing food quality and pilfering risk. Previous studies have proposed two non-mutually exclusive hypotheses; the optimal density model (ODM) and the habitat structure hypothesis (HSH). The ODM proposes that animals utilize low cache density to protect their valuable caches by transporting food far from food sources. The HSH proposes that animals utilize predation risk to protect their valuable caches by hoarding food in open areas. Here, we investigated the hoarding behaviours in Eurasian red squirrels Sciurus vulgaris by experimentally providing high-quality (walnuts) and low-quality (acorns) food, to examine if they follow ODM or HSH. Compared to acorns, squirrels hoarded walnuts in places further from the area where food was provisioned and in areas with low canopy cover. These results agree with both ODM and HSH, providing the first evidence that hoarding behaviour in Eurasian red squirrels is shaped by multiple factors.

BACKGROUND: Captive populations of penguins outside of their natural distributions are often maintained in outdoor facilities, such as zoos and aquariums. Consequently, such penguins in captivity are constantly exposed to mosquito vectors and risk of avian malarial infection during their active period from spring to autumn, which can be lethal to these naïve birds. Previous studies have investigated parasite prevalence in mosquitoes or penguins, but simultaneous investigations, which would be crucial to monitor the transmission dynamics and cycle within a facility, have not been done. To identify dominant lineages and trends, multiple-year surveys are recommended. METHODS: Avian malaria parasites (Plasmodium spp.) and related haemosporidia were tested in penguins and mosquitoes at an aquarium in Japan through multiple years from 2011 to 2018. Prevalence and dynamics were confirmed, and molecular analyses targeting the protozoal cytb gene were used to reveal the transmission cycle. Blood meals of mosquitoes were also identified using molecular methods. RESULTS: Parasite detection in penguins tended to fluctuate within an individual. Two Plasmodium lineages were consistently detected in mosquitoes that had fed on penguins and wild birds observed around the aquarium. Plasmodium lineage CXPIP09 was detected from both mosquitoes and penguins, suggesting active transmission at this facility. However, Plasmodium cathemerium PADOM02 was only detected in mosquitoes, which may be due to host, vector or parasite-related factors, or detection methods and their limits. Additionally, Haemoproteus larae SPMAG12 was detected from penguins, suggesting active transmission via biting midges. CONCLUSIONS: The mismatch in parasite composition between penguins and mosquitoes shows that multiple aspects such as captive birds, wild birds and vector insects should be monitored in order to better understand and control avian malarial infection within ex-situ conservation facilities. Furthermore, morphological analyses would be needed to confirm competency and infection dynamics of avian malaria parasites.

<title>Abstract</title> Increased boldness is one of the most prevalent behavioral modifications seen in urban animals and is thought to be a coping response to anthropogenic environmental alterations. Most previous studies have shown enhanced boldness manifested as changes in responses to humans approaching, such as reductions in flight initiation distance (FID). However, this includes two confounding factors related to “boldness,” that is, reduction of vigilance and habituation to humans. Confounding these totally different processes could lead to our misunderstanding of urban adaptation and how to properly manage urban wildlife. Here, we propose a simple framework to separate the two processes using two flight distance measures toward different approaching threats. We considered that the distance at which targeted individuals noticed an approaching object (i.e., alert distance, AD) was related to vigilance, whereas FID represented risk assessment, which is related to habituation. We applied a predictive framework using AD and FID to Eurasian red squirrels’ responses to multiple threats of different risk levels (i.e., humans, model predators, and novel objects). AD was shorter in urban individuals compared with rural ones but not different among the approaching objects. FID was shorter in urban individuals and also varied among the objects with the shortest FID toward humans, whereas rural individuals showed similar FID to the different objects. These results suggest that, although urban individuals showed reduced vigilance, they could still assess different risk levels. Our framework can easily be applied to many animals and could significantly improve our understanding of wild animals’ adaptations to urban environments.

The Siberian flying squirrel (Pteromys volans) produces up to two litters a year. To deliver second litters in breeding season, P. volans may have a postpartum estrus similarly to that of a variety of small mammals. If this were the case, females would have periods of elevated progesterone levels because of the formation of corpora lutea (CL) after postpartum ovulation. To test this hypothesis, fecal progesterone metabolite dynamics was investigated during lactation in this species using an enzyme immunoassay. In five of the six lactating females, periods of high fecal progesterone metabolite concentration were observed, and, furthermore, progesterone secretion patterns were periodic. Therefore, the source of progesterone during lactation could be arising CL from postpartum ovulation, indicating that ovarian activity was reinitiated after parturition and the CL that formed began secreting progesterone. This study thus showed that P. volans likely has the physiologic potential to mate during lactation.

The distance at which animals start to flee from approaching threats should reflects the degree of fearfulness, and thus, provides a useful measurement to evaluate animal personality and tolerance to human disturbance. Such metrics measurements, however, are mostly limited to open, high visible habitats, such as grasslands and urban parks. Alternative measurements are required for other types of habitats, such as typical forests. For arboreal species, we expect that a vertical escape distance (VED), the height at which animals stop climbing in a tree toward approaching threats, would reflect animal fearfulness. We compared VED and two commonly used metrics, alert distance (AD) and flight initiation distance (FID) in the Eurasian red squirrel (Sciurus vulgaris) towards human approach. We found that VED was significantly related with FID, but not AD. Data collection rate in VED was two to three times higher than that in the two previous metrics in vegetated areas. In natural environments, VED would also reflect the degree of fearfulness in arboreal species.

Describing the interactions among cavity breeders is key to understanding their breeding ecology. In this study the temporal difference in cavity use between the great tit, Parus major (Linnaeus, 1758) and the small Japanese field mice, Apodemus argenteus (Temminck, 1845) is investigated, as a first step for clarifying the interaction between bird and mammal cavity breeders. Forty-seven nest boxes were installed on tree trunks in two urban forests of Hokkaido Island, Japan, and the breeding nests of tits and mice were found in 34 and 11 boxes, respectively. The tits used the nest boxes throughout the breeding season, from May to July. In contrast, mice breeding nests were found in the last half of the breeding season, from July to October. Our results showed that field mice rarely used boxes during the tits’ breeding season. This study provides important information, such as temporal differences in breeding site use between tits and mice.

Urbanization has caused significant behavioural modifications in wild animals. Change in anti-predator behaviour is the most widespread example across different taxa in urban areas, which is probably due to a decrease in predation pressure and habituation towards humans. Seasonality or phenology has also been modified by urbanization since some resources in urban environments are highly controlled, for example, artificial feeding. Under natural conditions, anti-predator responses vary with seasonal variability in environmental and individual conditions. However, resource stability possibly reduces the seasonality of anti-predator behaviours in urban animals. Here, we compare the seasonal difference of flight initiation distance (FID), a measurement of anti-predator response, in Eurasian red squirrels Sciurus vulgaris between urban and rural areas in the Tokachi region, Hokkaido, Japan. Rural squirrels possessed FIDs two to three times longer than those of urban squirrels. We also found squirrels in rural areas lowered FID in autumn, but no seasonal difference was observed in urban squirrels. Our results suggest that continuous supplementary feeding may have buffered the seasonality in anti-predator response. In addition, strong habituation to humans may allow urban red squirrels to correctly assess human activity as benign rather than reacting unnecessarily.

2015年9月に，北海道において学生や若手研究者が中心となり，哺乳類研究に関する研究交流会を行った．参加者は，道内外合わせて31名で，学部生からポストドクターまで幅広い学年構成となった．参加者の年齢層，所属大学，研究対象種の多様性が本交流会の特色であり参加者間の活発な交流を後押ししていた．研究交流会の参加者に配布したアンケートでは，参加者は交流会自体に満足しており，「一年に一回」あるいは「半年に一回」のように定期的な開催を望んでいた．また，参加者は「研究交流会」だけではなく，「調査法に関する企画」や「進学・就職案内に関する企画」など様々な内容を望んでおり，学生のニーズに合わせた内容を企画する必要がある．一方で，参加者の約80％は交流会の開催を「知人から聞いた」と回答しており，内輪での開催と解釈されることは否めない．このため，今後の開催は広域のメーリングリストなどによって情報を普及し，参加者を広く募り，事前にアンケートを取り参加者の意見を反映させた内容を企画することも重要である．今回の交流会の成果と課題を反映することで，若手研究者が持つ研究意欲が活性化され，哺乳類研究がより発展していくのではないだろうか．

The small Japanese field mouse, Apodemus argenteus, is a semi-arboreal rodent that breeds in tree cavities. For this study, however, we observed its cavity-nesting behavior during the non-breeding season. In urban and riparian forests in April on the island of Hokkaido, Japan, we found two nesting cavities housing five and ten adult-like mice, respectively. Dissolutions of communal nesting advanced in late April. We consider that one reason for communal nesting is heat retention while overwintering, since communal nesting for heat retention is commonly shown in rodent species. Our results expand knowledge of cavity use by the mice during the non-breeding season.

タイリクモモンガPteromys volansは森林分断化の影響によって，個体数の減少や地域個体群の絶滅が危惧されている。森林分断化は動物に対してストレスやボディコンディションの低下を引き起こし，繁殖生理にも大きく影響するため，分断林に生息するタイリクモモンガにおける保全対策においては生態学的な視点のみではなく生理学的な評価も重要である。そこで，本研究では市販の酵素免疫測定法（EIA）キットを用いて，タイリクモモンガにおいて糞中プロジェステロン（P₄）測定が妊娠状態の評価に有効かを検証した。まず，EIAの実験が正常に反応しているのかを評価するために，糞中P₄を2倍段階希釈したものと標準曲線の平行性を検定した。その結果，階段希釈した糞中P₄と標準曲線の2つの回帰直線の傾きに有意な差はなかったため，平行性が示された。つまり，本種の糞中P₄測定は正確に行われたことがわかった。また，繁殖状態の推定が可能かを明らかにするために，P₄濃度が高いであろう妊娠期のメスとP₄濃度が低いであろう非繁殖期のメス，幼獣および成獣オスの間でP₄濃度を一般化線形混合モデルにより比較した。測定結果では，妊娠期のメスのP₄濃度は非繁殖期のメスや幼獣メス，成獣オスよりも有意に高かった。したがって，微量な糞からでも繁殖状態の変化に伴うP₄の変動を検出でき，市販のEIAキットを用いた糞中P₄測定によりタイリクモモンガの妊娠を推定し，生理学的な研究に応用することができるだろう。

タイリクモモンガPteromys volansは，フィンランドやエストニア，韓国などでは森林分断化の影響による個体数の減少が危惧されている．北海道の十勝地方においても，過去の森林分断化によって生息地が減少した上に，現在でもさらに生息地の分断化・減少が進行している．本種に対する森林分断化の影響を評価するには，生息確認方法を確立し，生息状況をモニタリングする必要がある．本研究では，糞による簡便かつ効率的な生息確認方法を確立するために，糞が頻繁に発見される場所の特徴や糞の発見効率を検討した．11ヶ所の樹林地（面積0.42–13.69 ha）において，それぞれ10 mの調査ラインをランダムに12本引き，両側4 m（片側2 m）の範囲で糞の有無を確認した．全ての樹林地で本種の糞が発見され，1ヶ所の樹林地あたりの発見糞塊数は平均9.7個，発見ライン数は平均6.2本であった．糞は胸高直径が太い樹木の近くでよく発見され，胸高直径24 cm以上の樹木から20 cm以内の範囲で糞を探すことが効率的であることがわかった．一方で，樹林面積は糞の発見ライン数に影響しなかった．そのため，樹林面積の大きさによって，調査努力量を変える必要はないと考えられた．本調査の結果から，面積に関わらず1ヶ所の樹林地につき5本程度のラインを引いて糞を探すことで，簡便かつ効率的に本種の生息を確認できることがわかった．https://www.jstage.jst.go.jp/article/mammalianscience/54/2/54_201/_article/-char/ja/

本研究はニホンモモンガPteromys momongaの生息に必須な資源であると考えられる樹洞について，スギCryptomeria japonicaやヒノキChamaecyparis obtusaの利用実態を明らかにすることを目的とした．本種の営巣確認を2005年3月から2010年4月の間に神奈川県丹沢山地の針広混交林で行った．その結果，ニホンモモンガの営巣は広葉樹の樹洞木20本のうち1本，針葉樹の樹洞木23本（スギ21本，ヒノキ2本）のうち8本で確認され，営巣のために針葉樹の樹洞木を多く利用していることが明らかになった．また針葉樹の営巣木はすべてスギであった．スギ・ヒノキにおける営巣木の樹高，胸高直径および樹洞の高さはそれぞれ25.6±3.7（平均±SD）m，50.3±11.2 cmおよび6.2±0.6 mで，営巣が確認されなかった樹洞木との間に有意差は認められなかった．<br>