臺灣鈍頭蛇對陸生軟體動物黏液的追蹤行為之探討

Terrestrial molluscs mucus trailing behavior of Taiwan slug snake, Pareas formosensis

林家蔚(Chia-wei Lin)

指導教授 ： 杜銘章

國立臺灣師範大學/理學院/生命科學研究所/碩士(2010年)

摘要

氣味追蹤是蛇類覓食時的重要行為，追蹤的效率高低直接影響到蛇類的生存。臺灣鈍頭蛇(Pareas formosensis)專食陸生腹足綱動物，並以有肺類(Pulmonate)為主食，前腮類(Prosobranchia)則不在其食物種類範圍內。本研究主要目的在探討臺灣鈍頭蛇對陸生腹足綱動物黏液之追蹤行為。我以Y型追蹤區檢測臺灣鈍頭蛇對有肺類的雙線蛞蝓(Incilaria bilineata)、斯文豪氏大蝸牛(Nesiohelix swinhoei)以及前腮類的臺灣大山蝸牛(Cyclophorus formosensis)黏液的追蹤行為，單一黏液的追蹤成功率結果顯示，臺灣鈍頭蛇對雙線蛞蝓的追蹤成功率(87.5%)最高，斯文豪氏大蝸牛(62.5%)次之，臺灣大山蝸牛(4.2%)最低並與作為控制組的蒸餾水(0%)無顯著差異。而追蹤偏好的結果顯示，在同時遭遇兩種不同黏液時，臺灣鈍頭蛇的追蹤偏好為雙線蛞蝓>斯文豪氏大蝸牛>臺灣大山蝸牛。將三種黏液放置0、15、30、60分鐘後，臺灣鈍頭蛇的追蹤成功率會隨黏液放置的時間增加而下降。在遭遇一橫向的黏液軌跡時，臺灣鈍頭蛇無法由黏液軌跡判斷獵物的前進方向，而是隨機選擇一方向進行追蹤。將雙線蛞蝓的黏液離心後所得到的小分子與大分子成分，以人工方式塗抹讓臺灣鈍頭蛇進行追蹤測驗，結果顯示臺灣鈍頭蛇對黏液小分子與大分子成分的追蹤成功率無顯著差異。本研究結果顯示臺灣鈍頭蛇對其偏好取食的腹足綱動物之黏液有較高的追蹤成功率及較顯著的追蹤偏好，臺灣鈍頭蛇無法由黏液軌跡判斷獵物的前進方向並進行追蹤，臺灣鈍頭蛇的追蹤成功率會隨黏液放置的時間增加而下降，而腹足綱動物對臺灣鈍頭蛇的抗拒掠食行為，與臺灣鈍頭蛇以黏液的何種成分為追蹤依據則尚待進一步的實驗去釐清。

關鍵字

臺灣鈍頭蛇 ； 黏液 ； 追蹤行為

並列摘要

Chemosensory search is one of the most important foraging behaviors for snakes. The survival of snakes is directly influenced by the efficiency of chemosensory search. Taiwan slug snake, Pareas formosensis, is a dietary specialist feeding on land snails, especially the Pulmonata. The aim of this study is to investigate the trailing behavior of Taiwan slug snake on the terrestrial mollusks mucus. A Y-shaped observation area was used to exam the trailing behavior of Taiwan slug snake to the mucus of terrestrial slugs (Incilaria bilineata) and two snails (Nesiohelix swinhoei and Cyclophorus formosensis). The results showed that Taiwan slug snakes preferred to trail the mucus of I. bilineata and N. swinhoei; The trailing rate was 87.5% and 62.5%, respectively. Taiwan slug snakes showed no significant preference between the trailing rate of C. formosensis (4.2%) and distilled water (0%). Testing by three kinds of mucus Taiwan slug snakes showed the greatest preference of I. bilineata, then N. swinhoei, and C. formosensis. I exposed each mucus to the air for 0, 15, 30, and 60 minutes, the result showed that the mucus trailing rates declined according to the increase of mucus exposure time. Taiwan slug snakes could not discriminate the direction of prey by mucus trails. Two parts of terrestrial slugs’ mucus were separated by centrifugation, namely small-molecules and macro-molecules. Nevertheless, Taiwan slug snakes showed no significant difference in tracing either small-molecules or macro-molecules.

並列關鍵字

Pareas formosensis ； mucus ； trailing behavior

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