- 學位論文
大雪山地區臺灣黑熊 (Ursus thibetanus formosanus) 的活動範圍和棲息地選擇模式
Home Ranges and Habitat Selection Models of Formosan Black Bears (Ursus thibetanus formosanus) in Dasyueshan Area, Taiwan
摘要
在人與野生動物共域的地區，高度人為活動可能使物種面臨生存及基因交流困難的問題，也提升潛在人獸衝突發生的機率。我們對於臺灣黑熊 (Ursus thibetanus formosanus) 在鑲嵌型地景中如何移動及選擇棲地所知甚少，故本研究利用2015至2019年於大雪山國家森林遊樂區內捕捉繫放的6隻臺灣黑熊 (2雌4雄) 的人造衛星追蹤資料，分析追蹤期間及不同季節大雪山地區黑熊之活動範圍、移動路徑以及棲地選擇模式。以最小凸多邊形法 (MCP, minimum convex polygon) 及核密度估計 (KDE, kernel density estimation) 計算活動範圍的結果顯示，雄性平均活動範圍大於雌性，且廣泛與其他個體重疊，然核密度估計顯示雌性間活動範圍不重疊。大部分個體 (n=4) 主要活動於大雪山200林道兩側，活動範圍亦受東側中部橫貫公路及西側密集的路網系統所侷限。黑熊的季節性活動範圍大小無顯著差異，但雄性個體在同年不同季節核心活動範圍的中心點平均間隔距離以冬春之間最大；在不同年相同季節的平均間隔距離，則以冬季落差最大。所有個體有一半以上的定位點 (51-93%) 分布在遊樂區及保護區以外之區域。雖由移動路徑可見黑熊鮮少跨越道路，然其中3隻個體 (1雌2雄) 曾於不同年間秋冬季出沒於農地及鄰近的森林環境中。以梯度提升樹 (GBRT, gradient boosted regression tree) 分別建構黑熊於追蹤期間及不同季節的第二階層棲息地選擇模型，顯示所有模型的顯著變量皆包含海拔、與道路最近距離，以及與步道最近距離，且彼此具交互作用影響。整體而言，熊不會迴避步道，並多活動於距步道5公里內之區域，於冬季更活動在3公里以內之區域，但皆避免於緊鄰道路處(400公尺內)活動。黑熊偏好海拔1,000至2,000公尺的區域，但在不同季節對海拔1,000公尺以下及2,000公尺以上區域則有不同趨避程度。在總追蹤期、夏季及秋季時，黑熊偏好利用NDVI值0.3至0.7之區域；春季時偏好利用距河流1.3公里以內的區域；冬季則對次生林有較明顯的利用程度。黑熊棲地選擇除了與季節性食物資源多寡及時空分布變化有關之外，也與人為活動因素有關。為確保大雪山地區臺灣黑熊族群的存續，建議持續此關鍵物種族群生態及重要食物資源之長期監測，並降低潛在人為干擾 (如不當開發、狩獵等)，以及強化森林性棲地之間的連結。
並列摘要
In area where human and wildlife coexist, frequent anthropogenic activities might pose threat to survival and genetic exchange of species, and also potentially increase human-wildlife conflicts. Understanding of how Formosan black bears (Ursus thibetanus formosanus) move and select habitat in a mosaic landscape is still unclear. This study investigated home range, movement path and habitat selection within whole tracking period as well as different seasons by using GPS data of 6 bears (2 females, 4 males) captured in Dasyueshan National Forest Recreational Area (DNFRA) from 2015 to 2019. Home range analyses by minimum convex polygon and kernel density estimation method showed that mean home ranges of males were larger than females and overlapped exclusively with other bears, while kernel home ranges did not overlap among females. Most of the bears (n=4) remained active in either northwest or southeast side of Dasyueshan Forest Road 200, with outermost boundaries of home ranges limited by adjacent road system and Provincial Highway 8. Home range size did not differ among seasons. Mean distance between home range centroids of different seasons within the same tracking year was farthest in winter-spring season among males. On the other hand, mean distance between home range centroids of the same season among different years was the longest in winter. 51-93% GPS locations of bear individuals were located outside the DNFRA and protected areas. Although bears seldom crossed roads, three of the individual bears (one female and two males) seemed to have approached farmland and adjacent forests in autumn and winter. Using gradient boosted regression tree to construct the second-order habitat selection models of bears at multiple temporal scales, distance to trail, distance to road and elevation were deemed significant factors in all models. Generally, black bears did not avoided areas within 5 km of trails, but avoided area within 0.4 km of roads. Black bears also preferred the elevation between 1,000 to 2,000 m, but seasonal difference was detected at avoidance of elevation < 1,000 m and > 2,000 m. Besides, black bears selected riparian areas in spring, preferred areas with thicker vegetation cover during summer and autumn, and selected regenerating forest in winter. Habitat selection of black bears might not only associated with masses and spatiotemporal distribution of seasonal food resources, but also influenced by human activities. To ensure the continual existence of Formosan black bears in Dasyueshan area, long term monitoring of bear population and food resources, reducing potential anthropogenic disturbances (such as inappropriate land development and illegal hunting) and securing connection between forested habitats are recommended.
參考文獻
延伸閱讀
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