北臺灣食肉目群聚食性變異研究

Abstract

中階掠食性動物（meso-predators）多屬廣食性（diet generalists）。在原有食物資源受到人為干擾時，中階掠食性動物往往可藉由調整食性來適應，這也可能是為何近年來研究發現中階掠食性動物在許多陸域生態系中逐漸取代了高階掠食者（apex predators）的原因之一。本研究以臺灣北部區域的食肉目物種：鼬獾 （Melogale moschata）、白鼻心 （Paguma larvata）、麝香貓 （Viverricula indica） 、食蟹獴（ Herpestes urva）為對象，利用排遺內含物形態，分析各類食物出現頻度，以探討陽明山地區、哈盆古道與福山植物園等地食肉目動物的食性變異。調查時間為2016-2017年間，每季2-3次到各樣區去採集排遺。上述物種中除食蟹獴外，其餘物種較難以排遺外觀辨認物種，因此我另外利用臺灣自然科學博物館所保存的動物屍體，採下獸毛製作毛鱗片標本，作為初步推斷排遺所屬物種之依據（部分樣本也透過另一研究計畫進行DNA物種鑑定）。北臺灣地區受到多種人為干擾（農業、遊憩、聚落、流浪貓狗等），有利於機會主義覓食策略，本研究的三個地點又以陽明山的人為干擾大於哈盆與福山兩地，因此我推測食肉目動物的食性應有明顯的地區差異：在陽明山地區，食肉目動物的食物種類可能較為單一、掠食功能性較不明顯、以及較有可能取食源自人類的食物。結果發現，相較於哈盆與福山，陽明山的食肉目排遺確實呈現食性組成較為單一的狀況，且較少以脊椎動物做為食物來源。同時，合併所有地點資料分析後發現，食肉目排遺距離道路越近，越有可能出現人造物，反之，離道路越遠，越可能出現脊椎動物，顯示食肉目動物之掠食功能，可能會隨人為干擾而下降。Meso-predators are typically diet generalists. Therefore, they may switch diets under anthropogenic influences. Diet flexibility is likely one of the reasons why meso-predators are replacing apex predators in terrestrial ecosystems, especially in urban and suburb areas. I studied diet variation of the carnivores (Melogale moschata, Paguma larvata, Viverricula indica, Herpestes urva) in northern Taiwan. My study sites included Yangmingshan National Park, Hapen trail and Fushan Botanical Garden. Yangmingshan National Park is likely under greater anthropogenic influences than Happen and Fushan. I visited each site 2-3 times every season from 2016 to 2017 to collect carnivore feces. I used a combination of feces morphology, guard hair morphology and fecal DNA (fecal DNA analysis belongs to a separate project) to help identify the species of the feces. I employed microscopic examination of fecal materials to quantify carnivore diets based on the frequencies of different food items in the feces. I expected substantial diet variation in the carnivores given that northern Taiwan is a region under strong anthropogenic influences (e.g. agriculture, recreation, settlements, feral dogs and cats), which should promote opportunistic foraging. As expected, carnivore diets were less diverse in Yangmingshan than in Hapen and Fushan, the former comprising mostly plants and invertebrates. Furthermore, the feces that were closer to major roads had a higher probability of containing human objects (e.g. plastic strings) whereas the feces that were farther away from major roads were more likely to contain vertebrate remains. My findings suggest that carnivores in areas under greater anthropogenic influences, such as Yangmingshan, are less likely to serve predatory functions.