臺灣低海拔食肉目動物之排遺DNA分析-兼論人為活動對食肉目動物食性之影響

Abstract

由於人類活動的擴張，人類與野生動物間的接觸日益頻繁。許多小型食肉目動物可以容忍相當高程度的人類活動，甚至還能因此獲取額外的利益，例如取食源自人類的食物，以及因其掠食者與競爭者避開人造環境而獲得額外的生存空間。本研究分析臺灣低海拔食肉目動物的排遺內含物，藉以檢測這些動物的食性是否隨人類活動壓力而改變。我針對五個常見小型食肉目物種（鼬獾Melogale moschata, 食蟹獴Herpestes urva, 白鼻心Paguma larvata, 麝香貓Viverricula indica, 石虎Prionailurus bengalensis）共161份排遺樣本，進行次世代定序（NGS）分析。我以排遺樣本點位擷取人類足跡指數（Human Footprint）做為人類活動壓力的指標。本研究結果發現，這些食肉目動物取食範圍極廣，包括數百個屬的植物、脊椎動物與無脊椎動物；其中更有46個植物屬有常見的農作物種類。不同物種的排遺內含物豐富度（fecal content richness；Chao1）存在差異，但食性組成相似度高。食肉目動物排遺內含物豐富度，以及排遺中含有人類相關序列（農作物與家畜序列、人類序列）的頻率，並不隨人類活動壓力高低而變化。雖然這些食肉目動物的取食行為並不隨人類活動壓力而改變，但這不代表他們沒有取食源自人類的食物；事實上，本研究結果顯示他們取食許多源自人類的食物種類。此外，在有人類活動的情況下，食肉目動物不只是能取食到新的食物，還可能接觸其他新的生物（例如寄生蟲、病源、微生物）。利用排遺DNA所蘊含的分子生物訊息，我們可以有效地偵測並瞭解人類與野生動物間之接觸程度與方式的改變。

Human-wildlife contacts are on the rise due to expansion of human activities. Many small-sized carnivores can tolerate human activities, and some may even benefit from anthropogenic food and man-made environments where their predators and competitors avoid. In this study, I investigated the fecal contents of carnivores in lowland Taiwan, and examined whether their fecal contents, and more specifically, their diets change with anthropogenic pressures. I performed fecal content analyses on 161 samples of five common small carnivores (Chinese ferret-badger Melogale moschata, crab-eating mongoose Herpestes urva, masked palm civet Paguma larvata, small Indian civet Viverricula indica, leopard cat Prionailurus bengalensis) with next-generation sequencing (NGS). To quantify anthropogenic pressures, I extracted human footprint values based on the locations of carnivore fecal samples. A wide range of dietary items are identified, including hundreds of genera across plants, vertebrates and invertebrates. Among them I also identified 46 plant genera that contain domesticated, crop species. The carnivore species have different levels of fecal content richness (Chao1) but their dietary compositions are similar. Neither fecal content richness or the occurrences of sequences that are related to anthropogenic activities (sequences of domesticated plants or animals, sequences of Home sapiens) changed with human footprint values. Although the carnivores did not appear to adjust their foraging behaviors in response to different anthropogenic pressures, it does not mean they were not feeding on anthropogenic foods. In fact, my findings suggest that the carnivores had access to a wide range of anthropogenic foods. More importantly, increased contacts with human not only allow the carnivores to feed on novel food resources, they may also expose these animals to other novel biological agents such as parasites, pathogens, and microbes. This study demonstrates the efficacies of using molecular information extracted from fecal DNA to inform potential changes in human-wildlife contacts.