|
 Back
Document Title:
Contaminants in Bats Roosting in Abandoned Mines at Imperial National Wildlife Refuge, Arizona, 1998-1999
AUTHOR(S):
Anthony L. Velasco Kirke A. King Jackie A. Record Ronald L. Kearns
REPORT NUMBER:
22410-1130-2N30
PAGES:
1 - 37
PUBLICATION DATE:
June 2001
ABSTRACT:
This report documents levels and potential effects of trace element and organochlorine
pesticide concentrations in four bats species collected from four abandoned mines on Imperial
National Wildlife Refuge (NWR) and from three southern Arizona reference sites. With the
exception of arsenic in the big brown bat (Eptesicus fuscus) and copper in California myotis
(M. californicus) and Yuma myotis (M. yumanensis), there appears to be little potential for
heavy metal related adverse effects in bats. Lead concentrations in Yuma myotis collected
from the Eureka Mine were 5- to 10-times higher than concentrations in samples from the
reference site; however, it is not known what concentrations of lead are associated with
sublethal effects such as impaired learning and behavior. Bats collected from an abandoned
mine in the intensively cultivated lower Gila River valley, approximately 137 km east of
Imperial NWR, contained significantly higher organochlorine concentrations, including
residues of DDT, than those from other sites; but, maximum concentrations were below
adverse effect thresholds.
The population of Yuma myotis roosting at Imperial NWR’s Eureka Mine, a mine complex
with multiple entrances, appeared to consist of several sub-populations based on chemical
profiles of bats collected at different entrances. Samples collected from three entrances
exhibited significant differences in whole body burdens of aluminum, cadmium, chromium,
copper, iron, manganese, selenium, and zinc. These unique entrance-specific contaminant
profiles suggested that: 1) individuals from each entrance either fed in separate Colorado
River habitats, and/or 2) bats from each entrance wintered in distinct environments, and/or 3)
contaminant profiles were modified at the roost site by ingestion or inhalation of dust
containing different ratios of various elements.
At Sheep Tank Mine, a reference site at Kofa NWR, barium, manganese, and zinc were
detected in soil at concentrations at least 10-times higher than previously reported in Arizona.
Big brown bats from the same mine also contained significantly higher concentrations of these
elements than big brown bats collected from three other sites. Metals acquired at the roost
site may be at least as important as those bioaccumulated through the food chain. Further
studies are scheduled to test the hypothesis that body burdens in bats may, in part, be a
reflection of ingestion of metals through the grooming process, and/or through inhalation of
metal-laden dust particles at the roost site. DEC ID No. 199820002
PUBLISHED BY:
U.S. Fish and Wildlife Service
DOCUMENT LINK:
http://www.fws.gov/southwest/es/arizona/Documents/ECReports/BATS_Imperial_NWR_%20EC_REPORT%201.pdf, 250 KB
|
