New York Natural Heritage Program
Little Brown Bat
Myotis lucifugus (Le Conte, 1831)
Mammals

Conservation Overview [-]
The little brown myotis has suffered significant population declines throughout New York. Although the negative trend in annual survey numbers leveled off between 2011 and 2013, it is too early to say if numbers are stabilizing. White-nose syndrome is a significant and pervasive threat to the persistence of this once common species.

Threats [-]
By far the largest threat to the little brown myotis in New York is white-nose syndrome (WNS) which was first discovered among bats in a cave in Schoharie County, New York in 2006. White-nose syndrome is caused by a fungus Pseudogymnoascus destructans (previously Geomyces destructans) that is often visible on the bats muzzle and wings (Blehert et al. 2009). The fungus may invade hair follicles and cause lesions under the skin (Blehert et al. 2009). Bats wake from hibernation and burn fat reserves that are needed to survive the winter and they become emaciated (Blehert et al. 2009). Extensive damage to their wing membranes and dehydration may also be contributing factors to mortality (U.S. Fish and Wildlife Service 2013). Survival over multiple years after exposure to WNS and healing of wing damage and infection has been documented in some individual little brown myotis at Ft. Drum, New York (Dobony et al. 2011).
Bats may be particularly sensitive to environmental toxins including those found in herbicides and pesticides. Elevated levels of persistent organic pollutants including especially PCBs, DDT, Chlordanes, and PBDEs have been found in little brown bats, in the Hudson River valley in New York (Kannan et al. 2010). The levels found in the bats were only 1 to 3 times less than lethal concentrations reported from previous studies (Kannan et al. 2010). Bats are highly susceptible to DDT residue and this chemical was widely used as a pesticide to control bat infestations in houses in the 1940s (USGS 2013). It was widely used as an agricultural pesticide in the 1950s and 60s until its agricultural use was banned in 1972. Since DDT is highly persistent (soil half-life is 2-15 years, aquatic half-life is about 150 years) (NPIC 1999), it can pose a threat to bats when there is exposure to trace residues remaining in the environment (USGS 2013). Extensive applications of insecticides and some bio control methods, such as Btk, could also pose an indirect risk to bats by reducing availability of insect prey.  Past long-term declines of the little brown myotis may be partly attributed to the use of pesticides (direct and indirect application) and to control measures targeting maternity colonies which may frequently occur in houses (Fenton and Barclay 1980).
If proper precautions are not used, cavers and researchers entering hibernacula may cause disturbance rousing bat colonies or can transport the fungus that causes WNS on their clothing (NatureServe 2013). Other potential threats may include climate change, commercial cave development, flooding and hibernacula collapse; habitat loss and fragmentation from development, hydraulic fracturing, and construction of new wind facilities; and direct mortality from wind facilities (U.S. Fish and Wildlife Service 2013).

Conservation Strategies and Management Practices [-]
Gating mines and caves can prevent human entry allowing the bats unobstructed access.  Following proper specifications and monitoring bat populations before and after gate installation are important, however, as gating can affect the airflow and temperature in the cave, making areas of the cave uninhabitable for certain species (U.S. Fish and Wildlife Service 2013). Buildup of debris at cave entrance gates can also have the same effect (U.S. Fish and Wildlife Service 2013).

Development and Mitigation Considerations [-]
Retaining snags and dying trees can provide summer roosting habitat for the little brown myotis.

Research Needs [-]
Research is needed to document summer roost locations in New York and to determine areas of the state with the highest local abundances. Ongoing winter hibernacula surveys are needed to monitor trends of the remaining populations.