New York Natural Heritage Program
Hoary Bat
Lasiurus cinereus (Beauvois, 1796)

Conservation Overview [-]
Much remains unknown about the habitat requirements and population trends of hoary bats in New York and this information is needed to accurately assess threats to the species in the state. Hoary bats are killed during collisions with wind turbines during the late-summer/early-fall migration period and it is not yet known whether this is a threat to the persistence of healthy populations in New York.

Threats [-]
Hoary bats are "migratory tree bats" that migrate rather than congregate in caves over the winter, and are not known to be affected by white-nose syndrome which has devastated cave bat populations in eastern North America. There has been a relatively high rate (30% of submitted carcasses) of rabies in hoary bats populations in some regions, such as the Midwest (Whitaker and Douglas 2006); however, the prevalence may be lower (10% of submitted carcasses) in New York (Childs et al. 1994).
Hoary 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 hoary bats made up to 46% of bat carcasses found at wind facilities in the eastern U.S (Arnett et al. 2008).
Bats may be particularly sensitive to environmental toxins including those found in herbicides and pesticides. They 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 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), it can pose a threat to bats when there is exposure to trace residues remaining in the environment (USGS 2013) or through bioaccumulation 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 hoary 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).

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 hoary bats in New York. Research identifying migratory patterns and pathways is needed, including studies of east-west movements (Cryan 2003).