Mercury in bats from the northeastern United States

Abstract

This study examines mercury exposure in bats across the northeast U.S. from 2005 to 2009. We collected 1,481 fur and 681 blood samples from 8 states and analyzed them for total Hg. A subset (n = 20) are also analyzed for methylmercury (MeHg). Ten species of bats from the northeast U.S. are represented in this study of which two are protected by the Endangered Species Act (ESA 1973) and two other species are pending review. There are four objectives in this paper: (1) to examine correlates to differences in fur-Hg levels among all of the sampling sites, including age, sex, species, and presence of a Hg point source; (2) define the relationship between blood and fur-Hg levels and the factors that influence that relationship including age, sex, species, reproductive status, and energetic condition; (3) determine the relationships between total Hg and MeHg in five common eastern bat species; and (4) assess the distribution of Hg across bat populations in the northeast. We found total blood and fur mercury was eight times higher in bats captured near point sources compared to nonpoint sources. Blood-Hg and fur-Hg were well correlated with females on average accumulating two times more Hg in fur than males. On average fur MeHg accounted for 86 % (range 71-95 %) of the total Hg in bat fur. Considering that females had high Hg concentrations, beyond that of established levels of concern, suggests there could be negative implications for bat populations from high Hg exposure since Hg is readily transferred to pups via breast milk. Bats provide an integral part of the ecosystem and their protection is considered to be of high priority. More research is needed to determine if Hg is a stressor that is negatively impacting bat populations.

Fig. 1

Sites sampled across the Northeast for Hg in fur and blood from bats (2006–2009)

Fig. 2

Least square means of Hg (μg/g, w) in fur from bats separated by species with standard error bars. Letters within the mean bars represent the results of post hoc Tukey HSD test; bars that share common letters do not differ significantly. *LACI hoary, LABO red, MYGR gray, EPFU big brown, MYLU little brown, PESU tri-colored, LANO silver-haired, MYSE northern long-eared, MYSO Indiana, MYLE eastern small-footed

Fig. 3

Least square means of Hg (μg/g, w) in fur showing sex and age at point source and non-point source sites with standard error bars

Fig. 4

Correlations between concentration of Hg in blood and fur from juvenile and adult bats

Fig. 5

Correlation between total Hg and MeHg in adult bats