Todd, C.M. (2012) Effects of prey abundance on seasonal movements of the Hawaiian hoary bat (Lasiurus cinereus semotus). MSc Thesis, University of Hawaii.
Abstract
This study investigated how biotic and abiotic factors affect seasonal altitudinal movements of Hawaiian hoary bats (Lasiurus cinereus semotus) in eastern Hawaiʻi. Bat activity, diet, aerial insect abundance, temperature, and rainfall were monitored bi-monthly at six sites from March 2009 to October 2010. I hypothesized that bat activity would be correlated with abundance of preferred insect taxa. An information-theoretic approach was applied to evaluate if bat activity was associated with one or more of these variables. Percentages of available insect taxa were highest at low elevations and declined with elevation. Moths dominated the insect fauna at middle and high elevations, although they were consumed significantly more than any other insect taxon at low elevations (P < 0.03). Coleoptera was consumed significantly more than any other insect taxon at middle elevations (P < 0.02). Insect taxa found in the diet of bats were proportional to their availability at low elevations (P = 0.9) and disproportional to their availability at middle elevations where a higher frequency of Coleoptera was in the diet (P < 0.001). This suggests that bats opportunistically forage at low elevations and selectively forage at middle elevations. Results from models indicate that temperature, rainfall, and insect abundance are nearly of equal importance among all sites (P = 0.05), and temperature and rainfall were nearly of equal importance as predictors at all elevations. A correlation between bat activity and insect taxon was significant at low elevations for Diptera (P = 0.02) but only marginally significant at middle elevations for Hemiptera (P = 0.08). No significant correlation between insect taxon and bat activity was found at high elevations. However, there was a correlation between bat activity and elevation that corresponded to changes in mean temperature and rainfall.