橙腹樹蛙（Rhacophorus Aurantiventris）生殖行為及生態學之研究

Abstract

我們從民國89年9月至90年11月，在台東利嘉林道11.5公里、海拔950公尺原始闊葉林中，以剪趾法 (toe clipping) 和催吐法進行橙腹樹蛙 (Rhacophorus aurantiventris) 生殖行為及生態學的研究。 研究結果顯示，橙腹樹蛙雌雄個體在體型、鳴囊等特徵上有差異，屬於雌雄二型性 (sexual dimorphism) (雌蛙SVL Mean=66.9㎜; 雄蛙SVL Mean=56.2㎜，P<0.01)。利嘉林道橙腹樹蛙繁殖季為4月~11月，繁殖季中的生殖活動強度與降雨量呈顯著相關。雄蛙在繁殖季時，會在積水樹洞週遭鳴叫，活動範圍不超過3公尺，雌蛙僅在產卵當天出現，交配系統屬於雄蛙控制的資源防禦系統 (resource defense mating system)。每夜生殖活動的雌雄性比 (OSR) 偏向雄蛙 (1:7)。 雄蛙會在葉面和樹枝上鳴叫，鳴叫時停棲的高度以1~2公尺範圍居多，少數個體會爬到6公尺高的植株上鳴叫。叫聲的種類可分為宣告叫聲、遭遇叫聲和壓迫叫聲等三種。當雌蛙受雄蛙鳴聲吸引而主動接近雄蛙形成配對，配對時由雌蛙背負雄蛙至倒木積水樹洞中產卵。雌雄蛙每次產一個白色橢圓形卵泡，每個卵泡平均含有 22.1顆卵粒，卵粒平均直徑為3.9㎜。 橙腹樹蛙產卵位置受限於積水樹洞的多寡和品質，卵泡孵化率高達83.8%。蝌蚪期的天敵以鼎脈蜻蜓幼蟲和食卵性艾氏樹蛙蝌蚪為主，成蛙在樣區內則較少發現天敵捕食。雄性橙腹樹蛙的食性以無脊椎昆蟲綱直翅目和蛛形綱為主。在生殖季節上，橙腹樹蛙跟艾氏樹蛙具有時間上的生殖區隔 (temporal reproductive partition) 現象。產卵場所的有無，可能是橙腹樹蛙族群的一重要限制因子。

From September 2000 to November 2001, we investigated the reproductive behaviour, calling activity pattern and diets of the orange-belly treefrog, Rhacophorus aurantiventris, from a subtropical primary deciduous forest in Taitung, south-eastern part of Taiwan. The study site was located at an elevation of ca. 950 m along the edge of Li-Chan Forestry Trail (22°48'30"N，121°01'30"E). All treefrogs were individually identifiable by toe-chipping. R. aurantiventris showed sexual dimorphism in which snout vent length (SVL) of females (66.9±2.18 mmn=10) was significantly greater than that of males (56.2±2.35 mm，n=117，t=13.9，P<0.001). The operational sex ratio (OSR) skewed toward males (♂:♀=7.0:1). Reproductive data from males and females suggest that the breeding season was from April to November in 2001 and reproductive activity was correlated with rainfall. No breeding peak was found in this study. The male calling activity was most intense, shortly after dusk and increased throughout the early evening hours (between 1800 and 2400 h). The calls may be separated into advertisement, encounter, and distress calls. The average number of eggs in one clutch ranged from 1 to 44, and the egg diameter ranged from 3.3 to 4.6 mm. The egg size was the largest, while the clutch size was the smallest among the Rhacophorus genus from Taiwan. The number of foam nests hatched approached 83.8% due to the limitation imposed by the amount and quality of water hole. Predation by the dragonfly larvae, Orthetrum triangular subsp., was the leading cause of tadpole mortality. Diets consisted of invertebrates of the classes Gastropoda, Arachnida, Chilopoda and Insecta. There was temporal reproductive partition between R. aurantiventris and Chirixalus eiffingeri. It was suspected that the quality of the oviposition site wasthe main limiting factor for the population size of this green treefrog in the wild.