高頭蝠(Scotophilus kuhlii)棲所利用與忠誠度

Abstract

蝙蝠棲所具有許多功能，如隔絕外界環境變動、避免蝙蝠遭到干擾、降低捕食壓力與增加個體間互動機會等。高頭蝠利用棕櫚科樹木的樹葉叢作為棲所，過往觀察發現高頭蝠群會分散利用一個地點內的數個棲所，棲所會長時間被蝠群利用，包括在不同年間都觀察到蝠群棲息，且各地點棲所被利用時間長短有所不同。本研究為瞭解高頭蝠的棲所利用與棲所忠誠度，使用持續觀察監測、捕捉標放與無線電追蹤等方式，探究各地高頭蝠棲所利用時間長短的差異，各地高頭蝠連續利用棲所的時間長短的差異與氣溫條件之關係，高頭蝠在年間重複利用同一棲地的狀況，高頭蝠個體對同一棲地內不同棲所的忠誠度，不同性別與年齡個體棲所忠誠度的差異等問題。研究結果顯示，由台灣北部至南部共八個高頭蝠棲息地點的棲所利用時間長短確實不同；高頭蝠群在各地棲所的利用總時間與開始利用時間都與氣溫條件有顯著關係，年均溫越高則棲所被連續利用的時間越長，反之越短：而捕捉標放的結果，則呈現標記個體在年間重複利用棲地的比例偏低，但棲地與棲所在年間都穩定被利用的現象。在棲所忠誠度方面，高頭蝠平均2~3天會變換一次棲所，但變換時仍會使用同一棲地中的其他棲所並會重複利用先前曾利用過的棲所，棲所平均利用時間、棲所連續利用指數與棲所利用多樣性指數等三種棲所忠誠度的檢視方法在雌雄性別間皆沒有顯著差異，但是成體的棲所平均利用時間與棲所變換指數則顯著大於第一年出生個體。高頭蝠雖然與其他葉棲型蝙蝠一樣都會頻繁變換棲所，但同一地點內可供利用的棲所狀況相當穩定且各棲所持續有蝠群利用，因此推測個體可能藉由變換使用同一棲地內不同棲所構成的棲所網絡進行互動，甚至形成分裂-融合(fission-fusion)的社群結構。

Roosts can serve several functions for bats, including isolation from environmental change and disturbance, reducing predation pressure, and increasing interaction between individuals. Asiatic lesser yellow bats (Scotophilus kuhlii) use leaves of palm trees as roosts. Previous observation found that these bats may use roosts for long period of time, which is unusual for leave-dwelling bats. However, it is not clear whether the same individuals would use these roosts continuously. To understand roost use and fidelity of S. kuhlii, we conducted direct observation, mark-recapture and radio-tracking to examine the following questions: (1) Differences in the total time of roost use by S. kuhlii at different latitudinal sites; (2) Relationship between the total time of roost use and temperature; (3) Inter-annual site fidelity of S. kuhlii; and (4) Sex and age differences of roost fidelity in S. kuhlii. Results showed that the total time and the starting time when a roost was used by S. kuhlii were positively related to temperature, i.e. the higher the temperature, the longer and earlier a roost was used. Low recapture rate indicated that banded bats rarely reused the same roosts and roosting site inter-annually, but the roosts were reused by the species inter-annually. On average, the banded bats switched roosts in the same roosting site every 2-3 days. There is no significant difference in roost fidelity between males and females, but difference was significant between adults and juveniles. Although S. kuhlii switched roosts as frequently as other foliage-roosting bats, the condition of the roosts they use is stable and all roosts were occupied by bats. Therefore, I propose that S. kuhlii may switch roosts frequently and use roosts at a site as a big roost network to facilitate social interaction and form a fission-fusion social structure.