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Tongan flying fox (Pteropus tonganus) activity patterns & associating cover types in American Samoa
Globally bats provide ecological services including pollination and natural pest removal. In American Samoa, the Tongan flying fox (Pteropus tonganus) is one of the primary animal species contributing to the success and regrowth of native forests. Trees used to create Samoan artifacts and cuisines benefit from the seed dispersal and pollination provided by these bats. However, habitat loss and human disturbance have caused population declines since the 1980s.
The American Samoa Department of Marine & Wildlife Resources (AS-DMWR) is using GPS tags to study flying fox movement and ecology. Information obtained from this research program aids bat conservation and contributes knowledge regarding understudied Pteropus spp. My thesis used these data from AS-DMWR to answer several important questions about Tongan flying fox ecology. The first objective of my research was to identify and quantify the diel patterns of Tongan flying fox commuting, foraging, and roosting activities. I used tri-axial acceleration data from the GPS tags to classify observations of bats to these specific activities. Then, I compared the percentage of time bats allocate to each activity during day and night using a one-tailed t-test. Results showed a significant difference in roosting only, with a p-value = 0.04 and t t0.05(1)4 = 2.95. Approximately 25% of roosting activities for tagged Tongan flying foxes occurred during the night and 75% occurred during the day. These results are consistent with the description of Tongan flying foxes as a nocturnal species. My second objective evaluated cover types in Tutuila, American Samoa where bats frequently perform these activities. Accelerometer and locational data obtained from GPS tags were used to identify segments of Tongan flying fox movement associated with the activities, roosting, foraging and commuting. Step-Selection Function (SSF), from the AMT (Animal Movement Tracking) R package determined cover type covariates that statistically correlated with segments of bat movement associated with specific activities. My results showed that Tongan flying foxes were likely to select locations within lowland forests for all three activities. Locations within coastal forests were also likely to be selected by Tongan flying foxes for commuting and roosting, while foraging was more likely to occur at locations near buildings and plantations.
In conclusion, the information presented in my thesis regarding Tongan flying fox activity patterns and associated cover types can help land managers and farmers develop efficient and effective management plans that reduce human and bat conflicts. Such plans could include delineating wind farm sites where risks of turbine strikes are low, identifying ways farmers could include flying foxes in their agricultural practices, and designating reserve areas needed to preserve this critical species.