The hoary bat is Missouri’s largest bat, named for the frosty look of its white-tipped fur. This species roosts in trees, 9–17 feet above the ground in the foliage, and occurs in Missouri in spring, summer, and fall.
The upperparts are yellowish to dark brown with a frosty or hoary appearance thanks to prominently white-tipped hairs. The underparts are yellower and with less white tipping. There is a conspicuous throat patch of long, tan-tipped hairs with brownish-black bases and a whitish shoulder patch that is usually continuous across the chest.
The wing and tail membranes are brownish black; on the upper surface, the wing membrane is pale yellowish brown along the forearm and partway down the fingers, indicating the location of the furring below. A cream-colored spot is visible on the forearm just behind the thumb.
The ears are short, broad, and rounded; they are tan with black rims and are furred both inside and out to the naked rim.
The wing membrane is furred both above and below from the body outward toward the elbow; on the undersurface, a strip of fur lies along the forearm to the wrist and about one-third of the way down the fingers.
The large, wide tail membrane is well furred on its entire upper surface, but it is thinly furred below on only the half nearest the body.
The hind feet are well furred above.
The fur on the neck is longer than the fur on the back, forming a slight ruff.
In addition to their ultrasonic echolocation cries, hoary bats also have a chatter that is audible to humans.
For your safety and the safety of bats, do not handle bats. Biologists who study bats receive special training and pre-exposure rabies vaccinations. Bats are not aggressive toward people but will bite in self-defense if handled. If you absolutely must handle a bat, wear heavy leather gloves. For more information about bats, see the bats group page.
Similar species: The hoary bat is easily distinguished from all other bats in Missouri by its large size and coloration. Also, it and its close relative, the eastern red bat, are our only bats with a well-furred tail membrane. Eastern red bats are quite different from hoary bats in coloration.
The silver-haired bat might be confused with the hoary bat, since both names imply silvery or whitish fur, but silver-haired bats are much smaller (about half the weight of hoary bats) and have black or dark brown fur with less prominent silvery tips.
Big brown bats are similar in size, but their uniformly brown color and lack of white fur tips distinguishes them from hoary bats.
Total length: 102–149 mm (about 4–6 inches); tail length: 50–65 mm (2–2½ inches); weight: 21–42 g (about 0.75–1.5 ounces); ear length: 19 mm (¾ inch).
Statewide.
Habitat and Conservation
Hoary bats inhabit trees, usually roosting 9–17 feet above the ground in the foliage. Rarely, they may roost in caves in late summer.
Hoary bats are the most widespread of all bats in North America. They range from the tree line in Canada south into Central America. They occur in all of the lower 48 US states.
Hoary bats are highly migratory. The northern part of their range is used primarily in summer and the southern in winter. Hoary bats are generally uncommon in all of their range; they are most common in the southwestern United States.
This species is considered relatively rare throughout Missouri, but acoustic detectors have suggested that they may be more common than previously thought; hoary bats tend to fly high and many are likely missed during mist-netting surveys.
Hoary bats occur in Missouri in spring, summer, and fall. In our state, they are most commonly seen here during migration, in May and September. Some young are reared here in summer.
Although a few hoary bats may stay in the northern part of their range all year, most migrate in fall to southern latitudes. The return migration occurs in spring. Although they typically travel individually or in small groups, large flocks have been reported.
In summer, true nursery colonies are not formed, but several individuals of the same sex may occur together.
During the day, hoary bats hang from tree branches by their hind feet. They choose a leafy site, usually 10–15 feet above the ground and at the edge of a clearing.
They begin to forage late in the evening. They fly above watercourses and grassy areas, following a very direct route. Their flight is fairly swift, strong, and high.
Food
Hoary bats feed extensively on moths and water boatmen. They also consume many wasps, dragonflies, beetles, and some mosquitoes.
Status
A Missouri species of conservation concern, listed as vulnerable; rated vulnerable to apparently secure across their North American range.
Life Cycle
Breeding occurs in late summer or early fall during migration. The length of gestation is unknown, but probably the eggs are not shed from the ovaries until spring. The young are born from late May to early July. There are usually 2 young in a litter. Females roost solitarily in foliage during pup-rearing. The young are free-flying around 1 month of age.
Control
Human Connections
As with other bat species, hoary bats help people by controlling populations of many kinds of pest insects.
Many people harbor a repugnance toward bats, in part due to their association with night, caves, and dark, “creepy” places, but hoary bats break the mold. They live and roost in trees, not too differently than many beloved birds and squirrels. Their fur, with its striking contrast between the brown base color with white fur tips, is genuinely attractive.
Their flight behavior might increase their risks of mortality at wind turbines. They are high-flying bats, and they may mistake the turbine structures as tall trees and attempt to alight on them.
The first part of the scientific name, Lasiurus, means “hairy tail.” This refers to the furred upper surface of the tail membrane that is characteristic of this genus. The last part, cinereus, means “ash colored” and indicates the grayish color. “Hoary” refers to the grayish white or silvery, frosty look of the fur.
Ecosystem Connections
The predator-prey relationship between bats and moths has led moths to evolve many fascinating ways to avoid being captured by bats. Several types of moths, upon sensing the sonar clicks of bats, will immediately, reflexively, engage in erratic flight patterns, or produce sounds that can confuse or jam the bats’ echolocation abilities.
While in most bat species, females give birth to only one, or maybe two pups per year, and have only two mammary glands, bats in genus Lasiurus can give birth to up to four and have four mammary glands. It is likely that these bats are subject to greater mortality than other bat species, as indicated by the higher number of young per female. Their relatively exposed roosts make them vulnerable to disturbances such as strong winds, rain, and predators.
Researchers have debated whether close relatives in South America and Hawaii are subspecies or should be considered different species; currently, they are designated as different species.
