Lasiurus cinereus

The three subspecies of Lasiurus cinereus recognized by Wilson and Reeder (2005) (L. c. cinereus, L. c. semotus, and L. c. villosissimus) have been elevated to species status by Baird et al. (2015). This has been adopted by the American Society of Mammalogists (ASM 2025) and Bats of the World (Simmons and Cirranello 2025). Also see Baird et al. (2017).

Baird et al. (2015, 2017, 2021) split Lasiurus into three distinct genera: Lasiurus (red bats), Aeorestes (hoary bats), and Dasypterus (yellow bats), but this arrangement has, to date, not been widely adopted by the scientific community under the argument that there is insufficient justification for changing the well-established zoological nomenclature for these species (see Ziegler et al. 2016, Novaes et al. 2018, and Teta 2019). Following the Global Bat Taxonomy Working Group of the IUCN SSC Bat Specialist Group (see Francis et al. 2023), the American Society of Mammalogists (ASM), and Bats of the World (batnames.org), this species is retained under Lasiurus.

This species is referred to as the Hoary Bat by Bat Species of the World and the Northern Hoary Bat by the American Society of Mammalogists.

Large range in North America; relatively high availability of roost sites (primarily in trees), but roosts support only solitary individuals or single females with young, so roost site abundance does not necessarily imply large population size; habitat availability has been reduced through deforestation, but much habitat remains (species uses managed forest landscapes and sometimes urbanized areas with large trees, as well as more natural habitats); overall population size is probably still large, but abundance is likely to be declining at a high rate due to a high level of mortality of primarily migrating individuals (estimated at tens of thousands annually) caused by turbines at wind energy facilities; this threat continues to intensify as wind farm installations across the range accelerates; reproductive rate of this species is relatively low, and its ability to sustain the current and anticipated level of wind-energy impact is doubtful.

Range encompasses most of North America, from southeast Alaska (Blejwas et al. 2014), British Columbia, southeastern Mackenzie, Hudson Bay, southern Quebec, Prince Edward Island, and Newfoundland south through Mexico to Guatemala (Hall 1981, Shump and Shump 1982, Cryan 2003, Wilson and Reeder 2005, Henderson et al. 2009). This species is rare or absent in most of the southeastern United States and in deserts of the U.S. Southwest.

In summer, northern hoary bats are uncommon in southeastern North America east of the Mississippi River and south of the Ohio River (Cryan 2003). Populations in the East are dominated by females, whereas males are more common in the mountainous regions of the West (Findley and Jones 1964). In the United States, adult females bear young in the northeastern, midwestern, and prairie states, and in small numbers south to Arkansas (Perry and Thill 2007), Louisiana, and Tennessee. Summer residents in central and eastern Oklahoma are dominated by females (Tyler and Scott 1982). Females are rare in California and the coastal Pacific Northwest in summer (Cryan 2003). Adults of both sexes occur during summer in the Black Hills and surrounding areas of the Great Plains (Cryan 2003). Wintering areas for northern breeders include the southeastern United States, western California, and Mexico (mainly males) (Cryan 2003), but some individuals remain as far north as the Great Lakes region and southern New England in winter. Elevational range in North America extends to at least 2,775 meters.

The number of distinct occurrences has not been determined using standardized/meaningful criteria, but this species is represented by a widely distributed and large number of collection and observation sites and locations (as defined by IUCN).

Over the long term, deforestation has reduced the available habitat for this species (e.g., Morrell et al. 1999, Whitaker et al. 2006). However, much suitable forest habitat remains, and hoary bats do not require pristine habitat (e.g., they may inhabit managed forests and sometimes also semi-urban areas that have ample large trees).

This is the bat species most commonly killed by turbines at wind energy facilities (Gruver 2003, Johnson et al. 2003, Fiedler 2004, Johnson 2005, Kunz et al. 2007, Arnett et al. 2008, Cryan 2011, Ellison 2012, Valdez and Cryan 2013, Frick et al. 2017). Fatalities at certain wind energy facilities may exceed 1,000 hoary bats per year (Arnett et al. 2008, Cryan 2011). Arnett and Baerwald (2013) estimated that about 247,000-634,000 hoary bats were killed at wind energy facilities in the United States and Canada during the period from 2000 to 2011 (38 percent of total bat fatalities). Available evidence indicates that wind turbines kill bats from various distant locations (i.e., from a broad area) rather than from localized subpopulations (Cryan et al. 2014). Wind energy is expected to expand from 61,000 MW in 2014 to 350,000 MW by 2030, so the cumulative impact from wind turbines on this species could be devastating. Although the size of the overall hoary bat population is unknown, the reproductive rate for this species is relatively low, and its ability to sustain the current and anticipated level of impact is doubtful.

Broadcast application of pesticides to combat forest/tree insect pests potentially has a detrimental impact on this species and its food resources; range-wide population impact is uncertain.

This species is not known to be impacted by white-nose syndrome (a cold-loving fungus that afflicts bats hibernating in caves and mines). This species may have a relatively high incidence of rabies (Whitaker and Douglas 2006), but the population impact of this disease is unknown.