Using digital photography and image analysis software to estimate the emergence of bats at Tou Santi Cave, Dominica, West Indies
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We applied a novel approach using still digital photography and image analysis to estimate emergence of bats at Tou Santi Cave, Dominica, West Indies. Although bat emergences are commonly studied, a population estimate of this lava tube has never been conducted. Known species inhabiting Tou Santi Cave include Brachyphylla cavernarum, Monophylhis plethodon, and Natalus stramineus. Using digital photography, we documented emerging bats at 30 second intervals for 130 minutes. Using image analysis software, we counted the number of bats in each frame and created 3 data sets. To find the total number of bats in each data set, multipliers were derived based on the 3 seconds it took the bats to pass from the bottom to the top of the framed area for the first 40 minutes, and 2 seconds for the remaining 90 minutes. The flight interval was a crucial element of this study. From these data we created 3 histograms to graphically summarize the number of emerging bats over time. The first 2 histograms represent bat counts at every 2 minutes. Combining all of the data to represent bat counts every minute resulted in a total estimate of 65,950 bats. Digital photography and image analysis software provide an efficient census technique for estimating the size of bat emergences. Copyright 2012 College of Arts and Sciences.
