東北角海岸陸生寄居蟹之分布

Abstract

陸寄居蟹為雜食性碎屑食者，並擁有背負移動、更換貝殼的習性，扮演物質與能量循環重要的角色，探討陸寄居蟹的生態學，有助於建構生態系統能量與物質循環之知識。本研究以陸寄居蟹的空間生態學作為主題，檢視海岸環境中的分布樣貌，並探索導致分布變異可能的環境因子，以較小的地景尺度環境因子解釋陸寄居蟹族群空間分布之差異。 分布調查的結果顯示在東北角地區，龍洞至鹽寮海濱公園北端，台２線向海側的海岸環境中，陸寄居蟹的優勢呈度依序為皺紋陸寄居蟹、凹足陸寄居蟹與短掌陸寄居蟹。到海距離，在三種陸寄居蟹之間有偏好差異。皺紋陸寄居蟹的族群量經估算約為51810到228047隻；凹足陸寄居蟹約為858隻。皺紋陸寄居蟹的族群穩定，性別比為1比1。 藉由廣義線性模型，可以發現，樣點周圍的底質類型，是對皺紋陸寄居蟹的相對豐度最主要的影響因子。而距海遠近、海岸線的自然度、與周圍自然植被面積等因子，也存在關聯性。由上述這些因素在模型中，可獨立於空間自相關之外，解釋了皺紋陸寄居蟹的分布變異。 本研究進一步發展了，利用拍照測量：螯指、步足末節長，與部分個體的前盾甲長，即可估測所有皺紋陸寄居蟹個體之前盾甲長的方法。此方法更簡便於直接測量前盾甲長，提供了未來陸寄居蟹族群調查方法，可改善動物福利，降低操作難度的調查策略參考。

Terrestrial/ land hermit crabs are omnivorous scavengers, carrying, move, and change gastropods shell, which play an important role of maters, nutrient and energy cycling. Investigating ecology of land hermit crab will improve the knowledge construction to maters and energy dynamic of ecosystem. This research focus on land hermit crabs’ spatial ecology, inspect the distribution pattern in sea shore area, furthermore, mine the potential environmental factors which induce the distribution variance, explain the variance of land hermit crabs’ population distribution by landscape scale environmental factors. Distribution survey shows that, Coenobita rugosus are more dominant than Coenobita cavipes and Coenobita brevimanus, in the seashore area, side by the Provincial Highway 2 (Taiwan) from Longdong to Yanliao ,in Northeast Taiwan. Three Coenobita species have different habitat preference on the distance to sea. Estimated population size of C. rugosus are around 51810 to 228047 crabs, and C. cavipes are around 858 crabs. C. rugosus have stable population status, sex-ratio is 1:1. The Generalized linear models reveal that major type of substrate around is the most important factor that affect relative abundance, and also distance to sea, natural shore length and natural vegetation coverage are correlate to relative abundance of C. rugosus. Forenamed factors can describe the distribution variance of C. rugosus, independently without spatial auto-correlation. This research also developed a method, which can estimate all sizes of C. rugosus shield lengths, by photo-measuring each crab’s chela movable finger and second left walking leg dactyls, and some samples’ shield length. This procedure is much convenience than directly measure the shield lengths, in hence provide a referance for future land hermit crab population survey strategy, which can bring down operation difficulty, and upgrade animal welfare.