New York Natural Heritage Program
Silver-haired Bat
Lasionycteris noctivagans (Le Conte, 1831)
Mammals

Conservation Overview [-]
This species is particularly difficult to survey and the statewide population numbers, trends and distribution remain unknown. Most records in New York are the result of collisions with wind turbines during migration. Summer records in the state are limited. The most extensive summer records have been documented from work completed by the US Army on Fort Drum Military Installation in northern NY. Also some exist from post-construction mortality monitoring on wind farms in central and northern NY. Other data on current abundance and distribution are lacking, yet necessary to assess the conservation status and the extent of threats to this species in New York.

Threats [-]
Silver-haired bats migrate rather than congregate in caves over the winter, and have not suffered the same dramatic population declines due to White-nose syndrome which has devastated cave bat populations in eastern North America. However, silver-haired bats have been found on occasion roosting in WNS-infected caves and mines and a silver-haired bat in Delaware was recently found to have Pseudogymnoascus destructans, the fungus believed to be responsible for causing WNS. It is unknown whether WNS poses a population-level threat to this species and more research is needed.
Silver-haired bats are killed when they collide with wind turbines in New York, particularly during fall migration. It is unknown whether the numbers of bats killed at turbines during migration is high enough to impact population numbers. One study reported that silver-haired bats made up 2-15% of bat carcasses found at wind facilities in the eastern U.S (Arnett et al. 2008), but higher percentages (up to 29%) have since been reported at several wind facilities in NY, particularly those in Clinton County (Jain et al. 2011).
Incompatible forest management practices could pose a threat; however, preferred characteristics of forest stand structure for this species are unknown in the east and more research is needed.
Bats may be particularly sensitive to environmental toxins including those found in herbicides and pesticides. 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 (U.S. Geological Survey 2013). It was also widely used (including aerial application) to control mosquitoes and agricultural pests in the 1940s and 50s. It was banned with a few exceptions in 1972. Since DDT is highly persistent, with a soil half-life of 2-15 years and an aquatic half-life of about 150 years (NPIC 1999), exposure to trace residues remaining in the environment can pose a threat to bats (USGS 2013) and bioaccumulation may occur when quantities of contaminated insect prey are consumed. 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.

Conservation Strategies and Management Practices [-]
Research indicates that raising cut-in speeds (i.e., wind speed at which turbines first start rotating and generating electrical power) of wind turbines during peak migration times may limit the number of migratory tree bats killed (Baerwald et al. 2009; Arnett et al. 2011).
In managed forests in the Pacific Northwest, the creation and preservation of snags and the maintenance of structural complexity in riparian areas and nearby uplands are important for silver-haired bats (Campbell and Hallett 1996). We know of no studies examining the response of silver-haired bats to forest management in eastern forests; however, retaining structural complexity in riparian areas and large snags, such as white pines, could be beneficial in eastern forests as well.

Research Needs [-]
Much remains unknown about the specific habitat requirements, reproductive behavior, and demographics of this species. The population trends, distribution, and local abundance also remain unknown and this information is needed to assess the extent of current threats to silver-haired bats. Developments in acoustic survey methods and call analysis may be especially beneficial for this hard-to-study species. Research identifying migratory patterns and pathways is needed, as well as further research into relationships between western and eastern groups to understand seasonal movements (Cryan 2003).