人類活動對臺灣低海拔地區小型食肉目動物食性之影響

Abstract

人類活動對野生動物可能有正面或負面的影響。小型食肉目動物（small carnivores）因為食性廣泛有彈性，常使他們得以適應高度人為干擾（如都市）的地區。臺灣低海拔地區人口密度高，人類活動對棲息於此的野生動物應有重要的影響。本研究目標物種為鼬獾（Melogale moschata subaurantiaca）及白鼻心（Paguma larvata taivana），兩種臺灣低海拔常見之小型食肉目物種。我利用行政院農委會特有生物研究保育中心提供之樣本，進行排遺形態分析以及毛髮碳氮穩定同位素分析，以量化這兩種食肉目動物之食性；同時，我結合樣本點位之人類活動量指標（Human Footprint），檢測人類活動對食肉目動物的影響。我預期（1）兩物種在食性組成與同位素值皆會有差異；（2）食肉目動物食性組成及動物性食物所佔比例（用以衡量其掠食功能性）會隨人類活動增加而有改變；（3）隨著人類活動量越高，源自人類之非自然食物越有可能成為食肉目動物食性的一部份，導致其碳、氮穩定同位素值的改變；（4）在人類活動量較高或道路影響較大的地點，食肉目動物排遺中人造物出現頻度會增加。結果顯示，鼬獾與白鼻心之間食性組成與碳、氮穩定同位素值皆顯著不同。食肉目動物食性受人類活動影響而有變化。鼬獾的氮穩定同位素值以及食性中動物性食物出現機率皆隨人類活動量上升而增加，反之，白鼻心食性並不受人類活動影響。食肉目動物排遺中人造物的出現機率不受人類活動量及道路的影響。此外，路殺資料顯示鼬獾體重隨人類活動量增加而上升，或許與其食性中動物性食物所佔比例上升有關；而狂犬病的有無則不影響鼬獾的食性組成，但會影響其氮同位素值並提高其空腸機率。本研究結果顯示了人類活動對食肉目動物食性的影響，應能為臺灣低海拔地區野生動物的經營管理與保育提供有參考價值之資訊。Anthropogenic effects on wildlife can be positive or negative. Small carnivores, with their broad and flexible diets, can often tolerate high levels of human activities such as urban environments. Taiwan’s lowland areas are heavily populated by human, which could have substantial impacts on wildlife. This study focused on two carnivore species wildly distributed across lowland Taiwan, the Formosan ferret-badger Melogale moschata subaurantiaca and Formosan masked palm civet Paguma larvata taivana. I combined microscopic analysis of fecal samples and stable isotope analysis (carbon and nitrogen) of hair samples from roadkillprovided by Taiwan Endemic Species Research Institute to quantify carnivores’ diets. I extracted human footprint values at the sample locations as a proxy for human activities to test the anthropogenic effects on carnivore diets. I predicted that: (1) the two carnivore species have different dietary compositions and stable isotope values; (2) the carnivores’ diets, and percentage of animal prey in their diets (a measure of predatory function), change with different levels of human activities; (3) with increasing human activities and consequently easier access to anthropogenic food resources, the carnivores’ stable carbon and nitrogen isotopes would change; (4) where human activities or road impacts are high, the occurrences of artificial materials in the carnivores’ feces would increase. The results showed that Formosan ferret-badgers and Formosan masked palm civets are different in both dietary compositions and stable isotope values. These carnivores changed their diets with different levels of human activities. Specifically, Formosan ferret-badgers had increased stable nitrogen isotope values, as well as percentage of animal prey in their diets, with higher levels of human activities; Formosan masked palm civets, on the other hand, did not seem to be affected by human activities. The occurrences of artificial materials in the carnivores’ feces were not affected by human activities or road impacts. In addition, I found that Formosan ferret-badgers in areas of high human activities tended to have larger body weights, which might be related to the higher percentage of animal prey in their diets. Rabies did not affect Formosan ferret-badgers’ dietary compositions, but altered their nitrogen isotope values and raised their probability of having empty intestines (starvation). This study revealed some of the potential anthropogenic impacts on carnivores’ diets, and can provide valuable information for wildlife management and conservation in lowland Taiwan.