Mercury Concentrations in Bat Guano From Caves and Bat Houses in Florida and Georgia

Abstract

Previous studies have indicated that several pollutants are bioaccumulating in insectivorous bats, including the heavy metal mercury. This has resulted in an increased presence of mercury in bat waste (guano). In this study, we collected bat guano from ten caves in Florida and Georgia and two bat houses in Florida and analyzed the samples for mercury concentrations (ppm). Since the predominant bat species using caves (Myotis austroriparius) versus bat houses (Tadarida braziliensis) were different, the objective of this study was to make statistical comparisons of the mercury concentrations among caves, between caves and bat houses, and between bat houses. We found no significant differences between caves and bat houses. The mean concentrations among caves were significantly different, as well as the concentrations between the two bat houses. These results show similar levels of mercury concentrations in bat guano in both predominant bat species that use these caves and bat houses in Florida and Georgia. But variability exists between all locations, which indicate that other variables (e.g., geographic hot spots for mercury exposure) also affect mercury concentrations in guano. This study provides baseline data for bat guano mercury levels, which is a barometer of bat health and potential bioaccumulation of mercury in guanitic food webs, such as those in cave ecosystems.