水鹿啃食紅檜樹皮與舔食礦鹽行為的觀察

鹿會隨著生活史週期各階段不同的礦物質需求，從環境中攝取不同的食物。針對台灣水鹿（Rusa unicolor swinhoii）近年來在楠溪林道週期性啃食紅檜（Chamaecyparis formosensis）樹皮的現象，過去的研究提出是長角期（解角及茸角期）公鹿為了攝取鈣質而啃食紅檜樹皮的假說。本研究從2017年11月開始在楠溪林道紀錄紅檜被啃食頻度並以自動相機監測水鹿族群豐度，在2018年11月開始放置礦物質鹽塊以做為轉移餵食（diversionary feeding），觀察長角期公鹿、硬角期公鹿、母鹿與幼鹿取食礦鹽行為。雖然各類別水鹿均有舔食礦鹽的行為，但長角期公鹿直接舔食礦鹽機率顯著高於其他類別水鹿（P<0.05），也顯著受到礦鹽站的吸引（P<0.05），且長角期水鹿被拍攝到啃樹皮的比例在放置鹽塊後下降。放置礦鹽前後整體水鹿相對豐度沒有改變，顯示上述的結果並非因水鹿的相對豐度改變而造成。因此，本研究推測長角期公鹿可能是基於長鹿角的營養需求，比起其他類別水鹿更需要礦物質。然而礦鹽放置期間，樹皮被啃食頻度相較於礦鹽放置前沒有明顯變化，可能是此地水鹿啃食樹皮行為已經多年，但本實驗目前放置礦鹽僅七個月，還無法有效改變這個行為。本研究建議未來可在啃食高峰期間提供礦鹽並重複數年，再評估轉移餵食對於降低水鹿啃食樹皮行為之效果。

關鍵字

鹿角生長；營養；礦物質；轉移餵食

並列摘要

Food items of deer may vary with its need for minerals in different life history stages. Formosan sambar (Rusa unicolor swinhoii) strip barks of Taiwan red cypress (Chamaecyparis formosensis) along the Nanshi Forest Road periodically in recent years. Previous studies hypothesized that male deer at antler-growing stage (including casting and velvet antler) ate barks of Taiwan red cypress for calcium. In November 2017, this research started to monitor the abundance of sambar using camera traps and bark stripping frequency on Taiwan red cypress along the Nanshi Forest Road. In November 2018, this research started diversionary feeding by providing mineral licks and observed behaviors of male sambar at antler-growing stage, males at antler stage, does, and fawns. Although all categories of sambar exhibited mineral-licking behavior, males at antler-growing stage had significantly higher probability of licking the mineral salt directly than any other category (P<0.05) and they were significantly attracted by feeding stations (P<0.05). Frequency of bark-tripping behavior of males at antler-growing stage caught by cameras was lower during the diversionary feeding period. Abundance of deer did not alter after the diversionary feeding, indicating that the above results were not due to change of deer abundance. Therefore, this research interpret that males at antler-growing stage may need minerals more than other categories of deer. However, the frequency of bark stripping did not significantly differ before and during the diversionary feeding. The diversionary feeding lasted only seven months, which may not be sufficient to change the bark-stripping behavior that has occurred in the study area for many years. This research suggests that future diversionary feeding should be conducted during the peak of bark-stripping and last for several years before evaluating the effect of diversionary feeding on lowering the bark-stripping behavior of Formosan sambar.