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

General Description [-]
Hoary bats are large weighing 20-45g (Shump and Shump 1982; Saunders 1988). Their pelage is yellowish brown to dark brown, and grey and tipped in light grey. The throat is yellowish in color and the longer neck hair forms a ruff (Saunders 1988). They have short, rounded ears that are edged in black and their tragus, or fleshy protuberance in the ear, is short and broad. The interfemoral membrane, or membrane that stretches between their legs and is used in flight, is heavily furred. Females, on average, are slightly larger than males (Williams and Findley 1979).

Identifying Characteristics [-]
The hoary bat may appear superficially similar to the silver-haired bat (Lasionycteris noctivagans); however, the hoary bat is much larger and lighter in color with grey-tipped yellowish-brown fur and a yellow throat. The silver-haired bat has pelage that is dark grey underneath and silver-tipped giving it a frosted appearance (Kunz 1982). They have a swift direct flight similar to red bats but are larger.

Best Life Stage for Proper Identification [-]
Adults may be easiest to identify.

Behavior [-]
Hoary bats are typically solitary, but they may forage among other species (Saunders 1988). They are a migratory species, however migration routes are unclear (Cryan 2003). They may exhibit some seasonal movements between eastern and western North America and there does not appear to be strong evidence for extensive movements between North and South America (Cryan 2003).

Breeding behavior remains somewhat of a mystery. One hypothesis exists that they may congregate to breed during late-summer/ early-fall migration at large trees and structures (Cryan 2008). Breeding is known to occur during migration and may continue on the wintering grounds (Shump and Shump 1982; Saunders 1988; Cryan 2008). Two young are born in June or early July (Saunders 1988). Young may cling onto the mother by day but are left hanging on a twig or leaf while she forages at night (Barbour and Davis 1969; Shump and Shump 1982). Young are able to fly after about a month and are independent soon after (Saunders 1988).

Both female adults and juvenile bats have been reported to enter torpor during the summer (Klug and Barclay 2013). Pups may balance energy needs for growing with the energetic costs of thermoregulation and mothers may use torpor during lactation in response to poor foraging conditions (Klug and Barclay 2013).

Hoary bats exhibit a swift direct flight that is similar to red bats (Shump and Shump 1982; Saunders 1988). They typically emerge from roosts to forage between 1 to 5 hours after sunset and may emerge closer to sunset in early and late summer (Saunders 1988).

Diet [-]
Hoary bats are moth (Lepidoptera) specialists. Ninety-eight percent of prey consumed was Lepidoptera in West Virginia, with lesser amounts of Hemiptera (Carter et al. 2003). Hoary bats may consume a more varied diet during migration. One study, during fall migration through Alberta, found that adult hoary bats preyed heavily on Lepidoptera (53%) but also on Hemiptera (41%); particularly water boatmen (Corixidae) (Reimer et al. 2010). While juvenile bats also preyed heavily on Lepidoptera with more variation in prey consumed. There are no known studies of the specific diet of hoary bats in New York.
The Best Time to See
The most reliable time to see a hoary bat is in the evening in June or July. They typically emerge from roosts later than many other species. They may be hard to distinguish in low-light conditions. See Behavior or identification Characteristics sections for distinguishing flight characteristics.
J F M A M J J A S O N D
Present Reproducing
The time of year you would expect to find Hoary Bat present (blue shading) and reproducing (orange shading) in New York.
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