蝌蚪越冬現象通常發生於高緯度或是高海拔地區，但在亞熱帶台灣的低海拔八卦山地區，卻有白頷樹蛙（Polypedates megacephalus）冬季蝌蚪的發現，因此本研究目的為：（一）調查八卦山地區白頷樹蛙的生殖物候學，確定是否有蝌蚪越冬現象；（二）紀錄野外越冬族群的發育模式；（三）經由實驗室實驗，探討溫度與食物量對於蝌蚪成長與發育的影響；（四）經由野外實驗，瞭解可能造成蝌蚪越冬的原因；（五）探討冬季前與冬季中變態的小蛙表現（脂肪含量與跳躍距離）。結果顯示，白頷樹蛙的繁殖季為每年三月至八月，且部分水池蝌蚪整年留存，表示八卦山地區白頷樹蛙蝌蚪確實具越冬現象，但屬於兼性越冬。低溫與低食物量皆會使蝌蚪發育緩慢，極低溫組（15℃）甚至在實驗結束時，仍無變態個體產生。野外操控實驗結果顯示在台灣低海拔冬季氣溫的影響下，食物量與溫度的交互作用是造成野外蝌蚪越冬的主因：高、中、低食物組分別有78%、28%、4%的蝌蚪在冬至前完成變態。變態後小蛙平均與最大跳躍距離，隨蝌蚪期食物量與溫度的增加而上升；高與低食物量組的小蛙體內脂肪量高於中食物量組。本研究結果顯示人為活動會影響到白頷樹蛙的生活史特徵，有無越冬的蝌蚪與小蛙在往後生理生態、族群動態上的關係，是值得深入探討的議題。 Generally, overwintering tadpoles is generally found in high latitude or elevation regions. In the subtropical lowland of the Bagua Terrace, Taiwan, however, Polypedates megacephalus tadpoles overwinter during mild winters. The purposes of my study were to 1) confirm the reproductive phenology of P. megacephalus in the Bagua terrace and find out if the tadpoles truly overwinter; 2) detect the developmental patterns of overwintering tadpoles; 3) to assess the effects of temperature and food levels on the growth and development of tadpoles using laboratory experiments; 4) unveil the possible mechanisms causing overwintering in the tadpoles using a field experiment and; 5) compare physical conditions (lipid content and jumping performance) of froglets. Results showed that P. megacephalus bred from March to August but tadpoles can be found year round, suggesting the tadpoles truly overwintered. Field surveys also revealed that the overwintering of tadpole is facultative. Low temperature and low food retarded the growth and development of tadpoles, and tadpoles at the lowest temperature never reached metamorphosis. Results from a field manipulative experiment suggest that the interaction of food levels and temperature is the most likely factor causing P. megacephalus tadpoles to overwinter. About 78, 28, and 4 % of tadpoles in the high, medium, and low food treatments metamorphosed as winter approached (December 23), respectively. The maximum and average jumping performance of froglets were positively associated with temperature and food levels. The lipid content of froglets in low and high food treatments were higher than that of the medium food treatment. My results revealed that human activity affects not only survival and movement but also life history trait of amphibians. Overwintered tadpoles represent another population when compared to tadpoles that metamorphose prior to winter. Future studies on the ecophysiology, population dynamics, and interactions between non-overwintered and overwintered tadpoles and froglets are ecologically and physiologically interesting.
