從鳴聲探討諸羅樹蛙(Rhacophorus arvalis)的雌性選擇

Abstract

鳴叫是兩棲綱無尾目動物的重要溝通方式。鳴聲可以反應出個體的體型或生理狀態，而雌性個體也可藉由雄性的鳴聲特徵來選擇配對的對象。本實驗收集分析雲林地區諸羅樹蛙(Rhacophorus arvalis)族群的鳴聲，探討雌蛙在群集展示場之間與群集展示場之內的雌性選擇依據，並檢測配對成功雄蛙的特質與體型之間的關係。 諸羅樹蛙的鳴聲依據頻譜特性、時間特性、出現時機以及伴隨行為，可以區分為釋放叫聲、壓迫叫聲與宣告叫聲A、B、C等，其中宣告叫聲A是雄蛙主要的求偶叫聲，宣告叫聲B及C則推測與求偶關係不大。具有較多雄蛙聚集鳴叫的群集展示場，其鳴叫持續時間較長(p=0.001)，鳴叫時間比例較高(p=0.0003)，雌蛙生殖強度也較大(p=0.017)。分析雌性選擇事件中配對成功與不成功雄蛙的體型和宣告叫聲A特徵，結果顯示成功雄蛙的頻率修飾幅度顯著小於不成功雄蛙(p=0.0177)，鳴叫速率顯著高於不成功雄蛙(p=0.0182)。將配對成功與不成功的雄蛙資料進行邏輯迴歸分析，可以得知宣告叫聲A頻率修飾幅度越小，一鳴叫中的脈波數越多，及在鳴叫陣中所佔的次數比例越高，則其成功配對的機率越大；鳴叫速率和鳴叫陣中的鳴叫數對於雄蛙生殖成功也有接近顯著的影響。以上五項和雄蛙配對成功與否相關的宣告叫聲A特徵當中，只有鳴叫速率和個體的體長之間有顯著的相關性，但屬於低度相關(p=0.0315)。 以上結果顯示諸羅樹蛙雌性個體會選擇具有較多雄蛙的群集展示場，進入展示場後推測會以宣告叫聲A的下列鳴聲特徵作為選擇雄蛙的依據：頻率修飾幅度、一個鳴叫中脈波數、鳴叫速率、一鳴叫陣中鳴叫數，以及在鳴叫陣中所佔的次數比例。In anurans, the most important way of communication is based on acoustic signaling. The advertisement calls of many anuran species play a critical role both for male-male competition and female preferences. Call types, call properties and the female preferences on male farmland green treefrogs (Rhacophorus arvalis) were investigated in this study. Based on recordings from fields, we identified five call types according to spectral and temporal properties; these included release call, distress call and three types of advertisement calls A, B, and C. Advertisement call A was recorded most frequently and was probably the most important one to attract females. Advertisement call B and C were presumed not to relate female selection. There was a positive correlation between the number of calling males in leks and time of continuous calling (p=0.001), percentage of time spent calling (p=0.0003), and the female reproductive intensity (p=0.017), respectively. Two call properties, frequency modulation and call rate, of advertisement call A differ significantly between successfully and unsuccessfully mating males (p=0.0177 for frequency modulation, p=0.0182 for call rate). The frequency modulation, number of pulses per call and the percentage of advertisement call A numbers per advertisement call bout were significant variables in predicting the mating success of males. Of all call properties, call rate was the only one that showed positive correlation with the male body size (p=0.0315). The results of this study suggested that female farmland green treefrogs choose leks with more males in it, and prefer males which call with less frequency modulations, higher call rates, more pulses per call, more calls per call bout or higher percentage of advertisement call A in call bouts.