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Source of Heavy Metals in Bats Studied
Date Posted: August 22, 2001With a possible exception or two, there is little historical evidence that bats roosting in abandoned mines are harmed by heavy metals found in the mines. Therefore, it is generally believed that heavy metals found in abandoned mines are not a threat to the resident bats. However, a study conducted by the Service’s Arizona field office has brought that assumption into question. The study showed that bats from three separate entrances to Imperial National Wildlife Refuges’s (NWR) Eureka mine, had significantly different levels of exposure to several metals. This suggests that the individuals from each entrance either feed or winter in separate areas outside the caves where heavy metal levels differ and/or individuals are being exposed to different levels of heavy metals at their roost sites within the mine.
At Kofa NWR’s Sheep Tank Mine certain heavy metals were detected in soil at concentrations at least 10-times higher than previously reported in Arizona. Bats from this mine contained significantly higher concentrations of these metals than bats collected from four other sites. Therefore, it is possible that metals acquired at the roost site may be at least as important as those acquired through feeding. Further studies are scheduled to determine whether the heavy metal found in bats may, in part, come from exposure at the roost site either from ingesting metals while grooming and/or inhaling metal-laden dust particles.