open access

https://doi.org/10.14943/doctoral.k15513

https://hdl.handle.net/2115/89986

ネパールにおけるナマケグマ（Melursus ursinus） : 生態、遺伝的多様性および人との軋轢

英語

2023-03-23

Hokkaido University

112 p.

The sloth bear (Melursus ursinus) is listed as a globally ‘Vulnerable’ species but has received very low conservation attention in Nepal despite their rarity and ecological importance. Their populations have declined across their distribution range mainly because of habitat deterioration and adverse human-bear interactions, including poaching and retaliatory killings. Large and well-connected habitats provide opportunities for gene flow and maintenance of high genetic diversity. Adequate genetic variation in a population is essential to increase their resilience against disease and pest, and flexibility to adapt in a changing environment. Habitat related features can regulate population growth through changes in availability of food, cover and safety. Thus, a thorough understanding of ecological requirements and genetic status is fundamental for developing effective strategies for sloth bear conservation. In Chapter I, I describe the distribution and determinants of habitat use by sloth bears. I used the occupancy method to account for imperfect detections during sign surveys and provide robust estimates of habitat occupancy. The model-averaged habitat occupancy estimate was 69% and the detection probability was 0.25. The probability of habitat occupancy by sloth bears increased with the presence of termites and fruits and in rugged, dry, open, undisturbed habitats. Results indicate that the sloth bear had a wide distribution in CNP with high occupancy in the central and northern parts of the park. In Chapter II, I explore the genetic status of sloth bears from Nepal. To elucidate the levels of genetic diversity and population genetic structure, I genotyped 127 samples using twelve microsatellite loci, identifying 37 individuals in an area of approximately 1000 km2. The sloth bear population in Nepal has a relatively low genetic diversity (HE = 0.48) compared to other bear populations across its range. I did not detect adequate evidence of genetic sub-structuring of the population across the landscape. Primers specific to bears were designed to amplify the fragment of mitochondrial control region from collected samples. Four haplotypes were observed with two haplotypes in CNP and one each in BNP and TJF. The resulting phylogeny indicated that sloth bears from Nepal are evolutionarily distinct from the other known sloth bear populations. In Chapter III, I elucidated the dietary composition of sloth bears from Nepal. An analysis of 194 fecal samples showed a high myrmecophagous diet dominated by termites and ants. Insect occurred in 95.36% of the feces and the fruits occurred in 25.77% of the feces samples. Insects had a high percentage frequency of occurrence across seasons. Fruits occurred at a higher proportion in monsoon season in CNP and its proportion was high in both monsoon and winter seasons in BNP. I did not detect food items of human origin or cultivated crops in the sloth bear feces. In Chapter IV, I explore the human-sloth bear interactions in Chitwan National Park. I report 74 incidents of adverse human-sloth bear encounters in 12 years period. Although 6.17 (SD = 2.96) human casualties from sloth bear encounters occurred every year, I did not detect significant trend of variation in conflicts with time or season. 80% of all these human-sloth bear conflict incidents were reported from the southwest sector of park in Madi municipality. Interviews with victims of human-sloth bear conflicts reveled their high dependence on forest and farm activities, low level of education. Most of the human casualties occurred when victims were walking alone in and around their village (40%), followed by activities in the forest (39%). Single bear was involved in 59% of the conflict events while in 31% of events a mother with a cub was involved. This is the first genetic study of sloth bears from Nepal. It is also a first-of-its-kind study combining occupancy methods, diet, and conflict to evaluate the ecological status of the sloth bears in Nepal. The information herein have important conservation implications. Reduction of genetic diversity can have severe consequences on individual fitness whereby their potential to adapt and evolve with changing habitat conditions may be seriously compromised. Safeguarding existing habitats and connecting habitat patches with corridors can be a key landscape-level conservation intervention. At a fine scale, identifying suitable habitats and conserving them to ensure that they do not pose a high risk from human and non-human predators, provide adequate shelter, and most importantly, supply diverse food resources in abundance (particularly termites, ants and fruit plants) can be a major intervention. Conservation of sloth bears in its northern distribution range can contribute to the enhancement of biodiversity and ecosystem services throughout the Gangetic plains, as they have been argued to be a better umbrella species and a proxy for carnivore monitoring. This study have breached the long information barrier on genetic and ecological aspects of sloth bears from Nepal that should be adequately considered in future strategies and action plans aimed at bear management and conservation.

2023-03-23

甲第15513号

博士(獣医学)

(主査) 教授 石塚 真由美, 教授 坪田 敏男, 准教授 下鶴 倫人, 教授 山﨑 晃司 （東京農業大学）

獣医学院(獣医学専攻)

博士論文

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