New York Field Office
Northeast Region

Special Projects

Environmental Contaminants in Bats

Final Report (pdf)
Paper published in Archives of Environmental Contamination and Toxicology

Beginning in 2007, bats in New York State began dying in significant numbers as a result of white-nose syndrome (WNS).  This disease is characterized by a white fungus on the muzzle, wings, and other body parts of hibernating bats.  Bats with WNS also exhibit unusual behavior during the winter months, including flying outside the hibernacula and clustering near the entrances of hibernacula.  Bats across the eastern United States and Canada are dying in large numbers; over one million bats are believed to have succumbed to WNS so far. 
Environmental contaminants, particularly a class of pesticides known as organochlorines, have been implicated historically in bat mortality.  It is also possible that more recently used classes of pesticides may be adversely affecting bat populations by interfering with metabolic, neurologic, or immune functions.  Emerging contaminants, such as detergents, discarded medicines, and plasticizers are also of increasing concern in the environment due to their widespread use. Bats may be more susceptible to the effects of contaminants than other mammals due to their high metabolic rates and annual hibernation cycles that require significant fat deposition.  Rapid depletion of fat reserves may mobilize fat soluble contaminants into the bat’s blood stream.
The Fish and Wildlife Service has been conducting a study to evaluate whether contaminants may play a role in worsening the effects of WNS by interfering with hibernation, metabolism, or immune function.  A disruption of these processes may increase sensitivity to the fungus associated with WNS.  We have evaluated contaminant concentrations in dead bats collected from New York, Massachusetts, Pennsylvania, Vermont, and New Hampshire.  Although a complete report is not yet available, our investigation has revealed fairly low concentrations of organic contaminants such as polychlorinated biphenyls (PCBs) and pesticides, such as DDT.  Mercury and chemicals such as polybrominated diphenyl ethers (used as flame retardants) are present in most bat samples.  Additional analysis is ongoing for emerging contaminants.

Analyzing bats at Hooper Mine

Analyzing bats at Hooper Mine, photo by USFWS

Environmental Contaminants in Eels:

Final Report (pdf)

American eel, Anguilla rostrata, are a migratory fish species with multiple life stages that migrate from freshwater to the ocean to spawn (a life history strategy known as catadromy).  American eel do not reach full maturity until after they complete their migration to their spawning areas, in the Sargasso Sea.  In fact, the exact locations of the spawning areas are unknown and researchers have never seen or collected sexually mature adult American eels and eel larvae.  In addition, researchers have had limited success in raising eels in a laboratory setting until recently.  In 2007, researchers at the University of Massachusetts-Dartmouth were able to mature adult American eels in the laboratory and get them to reproduce! 

Now that researchers have been able to rear American eel larvae in the laboratory, we can begin to explore factors that may be impacting reproduction in this elusive species.  One factor that needs more research is environmental contamination. 

The contaminant concentrations reported in American eel tissues are within the range of concentrations associated with impacts that have been documented in other fish species. These environmental contaminants have been shown to have biochemical, immunological, genotoxic (chemicals toxic to DNA), growth, survival, and reproductive impacts on various fish species.  The U.S. Fish and Wildlife Service’s New York Field Office and University of Massachusetts-Dartmouth Environmental Contaminants Off-Refuge Investigation, “Reproductive effects of contaminants on artificially matured and fertilized American eels, Anguilla rostrata” is currently investigating the role of parentally transferred contaminants on embryo and early larval development.  

Females were given weekly injections of hormone extract to mature them.  As the females get closer to ovulation they gain as much as 50% of their original weight as the eggs hydrate.  The bottom eel is just starting her hormonal injections and is at the onset of maturation while the top two eels are fully mature.

Mature female eels

Mature female eel (top), mature female eel next above immature female eel (bottom)


Eel larval development

Stages of embryo fertilization and development:
Post Fertilization (PF) – development after initial fertilization
Post Hatch (PH) – development after larval hatch

19 days post-hatch

Larval development: 19 days Post Hatch


Oliveira, K. and W. Hable.  2010.  Artificial maturation, fertilization, and early development of the American eel (Anguilla rostrata).  Canadian Journal of Zoology, 88:1121-1128.


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Last updated: March 21, 2016
All images by FWS unless otherwise noted.