外來種斑腿樹蛙與原生種白頷樹蛙對棲地之活動能力比較研究

Abstract

原棲地在中國及東南亞一帶的斑腿樹蛙，於2006年經由進口水草的途徑進入台灣。斑腿樹蛙與台灣原生種的白頷樹蛙體型外觀及棲息地相似，分布於海拔600m以下墾地環境。台灣至今尚未有研究顯示此兩種樹蛙，在棲息地或食物上具有競爭排擠的效應，但兩棲類資源調查團隊調查發現，斑腿樹蛙已逐漸擴散台灣西半部，2010年鶯歌碧龍宮周邊同時紀錄到白頷樹蛙及斑腿樹蛙，至2011年斑腿樹蛙已成優勢種。因此，本研究以兩棲類對於棲地利用，量化其行為能力，探討兩物種間的競爭排擠效應。實驗依棲息環境條件，比較草、木材、紅磚及混凝土等四種基質，配合四種坡度角度，及台灣夏、冬兩季溫濕度變化模擬，量測兩種樹蛙的吸附能力。並實測其體長、體重及跳高能力。實驗結果得知，斑腿樹蛙(♀)的跳高能力約為白頷樹蛙(♀)的95％，斑腿樹蛙(♂)的跳高能力約為白頷樹蛙(♂)的87％，證明斑腿樹蛙體型雖占優勢，但其跳高能力卻較差。以夏、冬兩季乾濕環境四個模組的比較，吸附能力由強至若排序為斑腿樹蛙(♂)、白頷樹蛙(♂)、白頷樹蛙(♀)、斑腿樹蛙(♀)，雄蛙的吸附能力比雌蛙強。兩種樹蛙對於四種基質的吸附力表現，由強至弱排序為紅磚、柳安木、混凝土、牛筋草，基質表面粗糙度與濕度也會影響蛙類的吸附能力。樹蛙的四肢趾端有吸盤，在移動過程為利用跳躍至基質上方再以吸盤吸附，與無吸盤之蛙類相比，其活動能力較佳，故在坡度工程設計上限可提高至60°。本研究乃探討此種生物利用陸水域空間之活動能力差異性，作為判斷斑腿樹蛙是否對白頷樹蛙利用棲地的影響與威脅，提供在棲地未來保育白頷樹蛙生態工程設計之參考依據，及營造不適合斑腿樹蛙生存的棲地環境。

Polypedates megacephalus, a tree frog species whose native habitats are China and Southeast Asia, invaded Taiwan via activities of importing aquatic-grass in 2006. The appearance and habitats of Polypedates megacephalus are similar to Polypedates braueri which is endemic amphibian species in Taiwan. Polypedates megacephalus inhabits agricultural ground at elevation below 600 meters. To date, previous studies in aiwan were limited to determine the effects of the competition on the habitats and food resources between the 2 species. However, according to Taiwan Amphibian Research Team's record, the population of Polypedates megacephalus has extended to western Taiwan gradually. In 2010 both species population were recorded at Yinko, Bi-Long Gong simultaneously, but in 2011 Polypedates megacephalus had became dominant species in that area. Therefore, in this study, we aimed to quantify the behavioral abilities of both species thoroughly in accordance with the habitat demand and investigate the effects on the competition to the habitats and food resources between them. We measured both species' body length, weight, and jumping ability in precision. Then, we conducted different experiments based on Polypedates megacephalus and Polypedates braueri's habitat conditions: their adhesion abilities responded to different materials like, grass, wood, brick and concrete, coordinated the angles of the slope and simulated the temperature and humidity in Taiwan's summer and winter. The results had shown that the jumping abilities of female Polypedates megacephalus is 95% of female Polypedates braueri and the male Polypedates megacephalus is 87% of male Polypedates braueri. This study shows that even though Polypedates megacephalus is physically larger then Polypedates braueri, but their jumping ability is worse. Base on summer and winter's dry and humility conditions on our four different simulated models, the study results demonstrated that from the strongest to worse adhesion abilities are, male Polypedates megacephalus, male Polypedates braueri, female Polypedates braueri, female Polypedates meagacephalus . We also tested both species adhesion abilities on 4 different type of materials; the easiest to worse adhesion materials are listed: brick, wood, concrete, to grass. We found out that the coarse of the material surface and the humidity of the material both will effect their adhesion abilities. Because of the suctions on both species' toe-pads, their motilities and jumping abilities are higher then other amphibian, therefore, in the engineering construction on the slope, we could raised the slope to 60 degree higher. Our research investigated the differences of amphibian motilities in terrestrial and freshwater habitats to determine whether Polypedates megacephalus cause effects and treats on habitat demand of Polypedates braueri, and this could provide reference basis for the design of ecological engineer for amphibian habitat conservation purpose in the future.