影響蛇類跨越能力的變因

Abstract

攀越不連續的底質對無四肢輔助的蛇類來說，是經常所要面臨的一個挑戰，尤其是陸棲蛇類與樹棲蛇類，在經過間縫大小不一的岩壁或者樹梢，必需充分利用骨骼、肌肉與外皮的相互協調來支撐前半段的身軀，以懸空方式跨越兩個支點。不同蛇類的跨越能力並不相同，多數的樹棲蛇類有較好的跨越能力。除了種類以外，許多其他的變因也可能會影響同種蛇類跨越能力的測量。本研究的目的在暸解不同的測量時段、性別和體長大小是否會影響同種蛇類跨越能力的表現。我們以數量較多的大頭蛇(Boiga kraepelini)、紅斑蛇(Dinodon rufozonatum)和赤尾青竹絲(Trimeresurus stejnegeri)作測試。結果顯示，跨越能力並不受晝夜生理活動週期的影響；雄性赤尾青竹絲跨越能力較雌性好，其餘二種蛇類不同的性別並不影響跨越能力；而體長大小從接近成熟的體長到接近最大記錄體長的個體，其跨越能力也不受影響，最大記錄體長的個體其跨越能力則會下降。

To crawl over gaps on the ground or especially above trees is usually encountered by terrestrial or arboreal snakes. Thus, it is valuable to possess good cantilever ability for these snakes. Generally, arboreal snakes can suspend their body without support better than other snakes. Other than this, many factors may affect the cantilever ability within species. The aim of this study is to clarify whether different time of day, sex or body length may influence the cantilever ability of snakes. We used three abundant species, Boiga kraepelini, Dinodon ruJozonatum, and Trimeresurus stejnegeri to test the above questions. The results indicated that cantilever ability was not affected by testing in the day or night. For Trimeresurus stejnegeri, males showed a better cantilever ability than females. Nevertheless, there is no difference between sexes in the other two species. No correlation between snout vent length (SVL) and cantilever ability if the SVL is around sexual maturity length. When the SVL reached the maximal length of that species, the cantilever ability was declined.