臺灣陽明山國家公園蛇亞目動物食性棲位探討

Abstract

掠食者具調節獵物族群及維持生物多樣性等生態系功能。蛇類具有高度物種多樣性及食性變異，但相較於哺乳類及鳥類，我們對其掠食功能所知較少。本研究針對北臺灣中低海拔森林生態系中常見八種共域蛇種進行系統性的食性分析。利用文獻資料、公民科學資料、以及路殺蛇類樣本之腸胃道內含物形態分析與鱗片穩定同位素分析，探討以下四個問題：（1）各蛇種的獵物多樣性與同位素食性棲位為何？（2）這些共域蛇種在廣食性－專食性梯度上如何是否分布的？（3）這些共域蛇種間食性棲位重疊度的樣態為何？（4）蛇種內個體體型大小是否影響其食性，亦即，體型越大的個體是否佔據越高的營養階，或在食性中有較高比例的大型獵物（脊椎動物獵物）？結果顯示，這些蛇種利用的獵物多樣性極高，包括來自不同營養階、利用不同碳源之獵物。蛇種均勻分布於廣食－專食性梯度（2種可視為相對專食性、3種可視為相對廣食性，其他3種則皆於中間），但種間獵物組成相似度高、同位素食性棲位重疊度亦高，顯示可能存在種間食物競爭。蛇類個體體型與食性間似乎無明確關聯性，但後續仍需有更多不同體型之個體的樣本來確認。本研究為臺灣常見蛇種建立基礎食性資料，有助於釐清蛇類在生態系中扮演的功能角色。Predators provide ecosystem functioning such as prey regulation and biodiversity maintenance. Snakes, despite having high species diversity and dietary variation, are less studied in terms of their predatory functions compared to mammals and birds. This study systematically examined the dietary niche of eight common snake species in the low- to mid-elevation forests of northern Taiwan. We compiled prey information of each snake species through literature review and identification of predation events from citizen science image databases. Additionally, we conducted gastrointestinal content and stable isotope analyses on roadkills to quantify their dietary compositions. With the combined information, we asked four questions: (1) what are the prey richness and isotope trophicniche of these snakes? (2) how are these sympatric snakes distributed along the generalist-specialist gradient? (3) what is the pattern of dietary niche overlap among these sympatric snakes? and (4) does individuals’ body size affect their dietary niche? Specifically, do larger individuals occupy higher trophic positions and consume a higher proportion of large-sized prey (vertebrate prey)? The results showed that these snakes utilize a diverse set of prey taxa from different trophic positions. The snake species are evenly distributed across the generalist-specialist gradient, with two specialists, three generalists and the remaining three exhibiting an intermediate degree of diet generalization. However, both the prey similarity and isotope niche overlap were relatively high among the snakes, suggesting potential food competition. No clear association was found between individuals’ body size and their dietary niche, which should be confirmed in the future with a larger sample size that better reflects intraspecific body-size variation. This study provides dietary information for common snake species in Taiwan and offers insights into their functional roles.