翡翠水庫台灣穿山甲洞穴棲地研究

Abstract

本研究於2003年8月至2004年9月，在台北縣翡翠水庫集水區中劃設6條穿越線，沿線定期調查台灣穿山甲 (Manis pentadactyla pentadactyla)的洞穴數目，並紀錄洞穴開口方位、洞穴周圍坡向、洞口傾斜度、周圍坡度、洞穴直徑、洞穴進口角度、洞穴長度、周圍植物覆蓋度、周圍枯葉層厚度、周圍植群類型、周圍林下植群高度及洞穴內外溫度。研究地內包含針葉人工林、闊葉人工林、天然(次生)林及竹林四種棲地。研究地土壤之粘粒與坋粒之重量百分比超過80%，屬於含砂量少的粘質土與壤質土。研究期間共發現340個穿山甲洞穴，其中可獲得測量值的洞穴計294個，包括2003年8月發現之舊洞穴275個、2003年9月後發現之新洞穴19個。洞穴新增之時間為2003年11月及12月，2004年3月及4月。穿越線上之洞穴平均密度為56.7 個/ha.，其中以闊葉人工林中最高 (64.5 個/ha.)，其次為針葉人工林 (53.0個/ha.)與天然(次生)林 (51.6 個/ha.)，竹林中最低 (46.7個/ha.)；不過四種棲地之面積百分比與洞穴百分比差異均不顯著，亦即穿山甲既不偏好也不排斥在任何一類棲地挖掘洞穴。穿山甲洞穴之空間分布不隨機，且有聚集分布之現象。穿山甲洞穴平均開口方位為237.9±76.2°，洞穴周圍坡向平均為237.4±90.2°，均偏向西南方，洞穴開口方向與坡向呈顯著之正相關。洞穴平均傾斜度為32.5±15.4°，周圍之坡度平均為24.9±8.0°，平均直徑為17.3±3.0 cm，平均進口角度為 -28.4±14.0°，洞口傾斜度與洞穴進口角度有顯著正相關。穿山甲之洞穴平均長度為80.6±48.3 cm，洞穴周圍植物覆蓋度為62.4±24.7%，周圍枯葉層厚度平均為1.1±1.6 cm，周圍植被類型以草本最多(56.9%)，周圍林下植群高度平均為68.9±84.8 cm，且周圍1m內之林下植群高度大致相同，可為穿山甲提供良好之隱蔽性。穿山甲洞穴內之日均溫 (20.7±3.9℃)顯著高於洞穴外(19.7±5.3℃)；洞穴內之日均最高溫 (21.0±4.1℃)顯著低於洞穴外 (23.1±6.4℃)；洞穴內之日均最低溫 (20.4±4.0℃)顯著高於洞穴外 (17.4±5.2℃)；洞穴內之日均最大溫差 (0.7±0.9℃)顯著低於洞穴外 (5.7±3.0℃)，顯示洞穴可對穿山甲提供一溫度穩定之環境。

I studied the burrow density; burrow orientation and slope aspect; slopes of burrow and ground; burrow diameter, slope of burrow tunnel, burrow length; vegetation coverage, litter depth, vegetation type, and vegetation height around burrows; air temperature outside and inside burrows of Formosan pangolins (Manis pentadactyla pentadactyla) along six transect lines at Feitsui Reservoir Watershed from August 2003 to September 2004. The study site was classified into four habitat types: coniferous tree plantations, broadleaf tree plantations, secondary forests and bamboo plantations. The percentage of slit and clay of soils in the study site was all over 80%, which was classified as clay or loam. There were 340 burrows found during the study period; but only 294 burrows had complete measurements which 275 old burrows were found in August 2003 and 19 new burrows after September 2003. All the 19 new burrows were found in November and December 2003, and March and April 2004. Mean burrow density within study site was 56.7 burrows/ha. Burrow densities did not significantly differ among coniferous tree plantations (53.0 burrows/ha.), broadleaf tree plantations (64.5 burrows/ha.), secondary forests (51.6 burrows/ha.) and bamboo plantations (46.7 burrows/ha.). The distribution pattern of burrows was found significantly aggregated. Mean burrow orientation (237.9±76.2°) was significantly correlated with slope aspect (237.4±90.2°) of burrows. Mean slope of burrows was 32.5±15.4° and mean slope of ground around borrows was 24.9±8.0°. Mean burrow diameter, slope of burrow tunnel, and burrow length were 17.3±3.0 cm, -28.4±14.0°, and 80.6±48.3 cm, respectively. There was a significantly positive correlation between slope of burrows and slope of burrow tunnels. Mean vegetation coverage and mean litter depth around burrows were 62.4±24.7% and 1.1±1.6 cm, respectively. The most common vegetation type around burrows was herb (56.9%) and mean vegetation height around burrow was 68.9±84.8 cm, suggesting that the vegetation around burrows might provide good shelter for pangolins. Both mean daily temperature (20.7±3.9℃) and mean minimum daily temperature (20.4±4.0℃) inside burrows were significantly higher than air temperature outside burrows (19.7±5.3℃ and 17.4±5.2℃ respectively). On the contrary, both mean maximum daily temperature (21.0±4.1℃) and mean daily maximum fluctuation of temperature (0.7±0.9℃) inside burrows was significantly lower than those outside borrows (23.1±6.4℃ and 5.7±3.0℃ respectively). Results indicated that burrows could provide a more stable thermal environment for pangolins.