See What You Can Learn about Bats in Colorado


  • Bats are insectivores and rely on a good source of insects, as one bat can consume between 1,200 and 4,500 insects a night.
  • Bats depend directly on vegetation for cover.
  • Two species of Lasiurus both roost in trees, as does the silver-haired bat, but most other species select roosts by physical features like rock overhangs, crevices, caves, mines, or human-made structures.
  • A number of species use buildings, bridges, mines, and other structures.
  • Water is an essential feature of habitat for most bats. Nearly all species come to water (a pond, still pool or quiet eddy in a stream) to drink.


  • Flight in mammals is unique to bats.
  • Birds evolved flight independently of bats, and although both are flying vertebrates, they differ considerably in terms of loco-motor anatomy.
  • Unlike birds, which use only chest muscles to power flight, the wings of bats are powered by both chest and back muscles. The down stroke is driven by the chest muscles and produces the force keeping the bat airborne, whereas the force created by the back muscles produces forward movement.
  • Most bats drop into flapping flight from a hanging position.
  • Some bats crawl to an edge of a rock face and hop into flight.
  • When landing, bats usually survey the area using echolocation or vision, and then perform a flip in the air, hooking their claws onto the roost substrate to stop.
  • Their ability to alter each wing’s movement independently of the other lets them to roll or slip to one side, literally on a dime.
  • The second through fifth fingers traverse the wing membrane, which allows for precise control of the lift produced by the wing.
  • The heart rate of a flying bats may reach as high as 1,200 beats per minute.
  • Flying bats consume energy three times as fast as the highest recorded rates of other animals their size, but flight is so efficient that a bat uses less than one-fourth the energy of others their size.
  • Bats are highly adept at negotiating in extremely tight spaces. In one laboratory experiment, a Dent’s horseshoe bat—with a wingspan of about 10 inches—was released into a box measuring approximately 3 feet by 3 feet by 1 foot. Calling it “one of the most impressive demonstrations I have ever witnessed,” Dr. Brock Fenton reported that the bat, “flew at length without touching the walls, ceiling, or floor.”


  • Echolocation is a means of close-range navigation. (High frequency sound dissipates or is absorbed in air quickly.)
  • Most bats echolocate, but not all bats hunt with echolocation.
  • Echolocation involves two processes. First, the bat must produce and transmit calls; then it must receive and interpret echoes.
  • Calls of most bats are produced in the larynx or voice box. Bats may use more than one frequency during echolocation.
  • They can use FM (frequency modulated) calls that start at one frequency and drop or sweep down to another. Or they can use constant frequency (CF) calls, dominated by one frequency. Most species use a combination of FM and CF calls.
  • Most bats emit vocalizations through their mouths, which explains why most bats have their mouths wide open while in flight.
  • New World leaf-nosed bats emit vocalizations through their nostrils.
  • Vocalizations can differ in intensity between species of bats. Low-intensity calls can be compared to someone whispering in your ear, while high-intensity calls are worse than someone screaming.
  • A little brown bat generates sound with the intensity of a smoke detector. These calls are ultrasonic, which is above the range of human hearing.
  • Longer pulses are better suited to locating smaller objects.
  • Shorter calls are better for collecting detailed information about a target.
  • Hoary bats have a call rate of 3-10 calls per second while hunting, which increases to 200 per second as a bat closes in.
  • This high-rate vocalization is referred to as a feeding buzz.
  • Their ears exhibit a wide variety of sizes and shapes, apparently specialized to increase effectiveness of interpreting the echo.
  • A bat can obtain information such as size, shape, texture, speed, and direction of movement of the target from their echo calls.


  • All Colorado bats are insectivores.
  • Little brown bats have been known to catch and eat more than 150 mosquitoes in less than 15 minutes.
  • They chew their food up to seven times per second.
  • Bats generally fly low over lakes or streams to drink.
  • Bats living in deserts do not drink at all. They rely on insects to provide them with the water they need.
  • Fruit eating bats are efficient pollinators and seeders.
  • Bat vegetarians specialize in eating the high-energy parts of the plant, such as fruit and nectar.
  • No bat is specialized to eat leaves (folivory). Leaves are an abundant resource, but their energy mostly is tied up in cellulose, which mammals cannot digest.
  • Leaf-nosed bats have not stuck with vegetarianism. Fruit-eating bats gave rise to specialized carnivores.
  • “False vampire bats” of the New World tropics are not vampires at all, but are carnivores that eat rodents, bats, birds and sometimes other bats (including the Colorado’s Hoary bat).
  • The fringe-lipped bat is specialized to locate and capture frogs, especially noisy males calling for mates.
  • True vampire bats, about three species of bats, are all from Latin America and eat only blood. Two species feed mostly on the blood of birds, while the common vampire specializes on mammals. After making a quick incision with their razor-sharp incisors—often the neck, shoulder, ears, hips, legs or around the hooves—the bats inject an anticoagulant and drink their fill.
  • They drink less than a half ounce of blood at a meal.
  • They are contributors to the paths of disease, such as bacterial, parasitic, and rabies infections.

Roosting and Hibernation

  • Most Colorado bats migrate to some extent, although little is known about this behavior. The advantages of having separate summer and winter roosts must be substantial, however, to justify sometimes lengthy commutes.
  • About half of Colorado’s bats make only local migrations and hibernate in the state.
  • Hibernacula (hibernation roosts) of some species never have been located.
  • Hibernacula are occupied much longer than other roosts, up to four months or more in some species, during the coldest months.
  • Hibernation usually is a bat’s deepest torpor, and the rate of fuel consumption is greatly reduced.
  • In some species, body temperature may drop to near freezing
  • In hibernating, little brown bats’ temperatures have been recorded at 30° F, with icicles developing on the bats’ fur. The heart rate of hibernating bats may drop to 10 beats per minute, compared with well over 1,000 when the animal is in flight.
  • Torpid bats have survived submersion in water for an hour at a time with little effect.
  • Brazilian free-tailed bats, located in the southwestern US, travel 1,000 miles or more into the interior of Mexico each fall, which is probably the longest migration of any bat in the world.
  • Bats are strongly heterothermic. (Body temperature varies wildly.)
  • Bats achieve and maintain body temperatures appropriate to their current physiological and behavioral needs, conserving energy.
  • When they are actively feeding, metabolic activity and body temperature are high. When they are resting, both are low.
  • Temperature is adjustable to the variable demands of activity. This process of resting under lowered metabolic activity and body temperature is termed torpor.
  • Bats may enter torpor for a few hours or several months. The intensity of torpor ranges from shallow to deep.
  • Deep, long-term torpor in winter is termed hibernation. Periods of torpor are spent in a roost.
  • Most of Colorado’s bats prefer caves, fissures, mines, and old buildings as roosts. Several species, however, use tree roosts.
  • Red bats of the eastern plains prefer deciduous trees near rivers and streams.
  • The hoary bat and the silver-haired bat roost in deciduous riparian woodland or higher coniferous forests, where they blend with pine needles, bark, and lichens.
  • Day and night roosts usually are separate and often distinctive.
  • Night roosts (loafing bats) serve as temporary havens for active bats.
  • Local species use a bi-phasic pattern of foraging activity, in which individuals emerge to feed, then night roost for a few hours, then feed again and finally retire to a day roost.
  • Because night roosts are adjacent to feeding grounds and feeding areas, night roosts may be in clearings near homes, porches, eaves, and haylofts. Loafing sites are often marked by tiny piles of droppings.
  • Day roosts usually provide more protection than night roosts, especially from changes in temperature.
  • The Brazilian free-tailed bats roosts of males, females, and young are strongly segregated during the summer, to increase available feeding opportunities.
  • The separate nursery and “bachelor” colonies are often hundreds of miles from each other, allowing the bats to exploit different habitats and independent food resources.
  • Some biologists believe that these bats may be synchronizing their internal clocks with the solar cycle.


  • Reproductive strategy of bats, like that of humans and most other primates, is based on the quality of offspring, not the quantity.
  • Bats often are highly sociable, forming large breeding colonies.
  • Courting behaviors involve vocal exchanges and body language.
  • Copulation often includes soft chattering and mutual licking.
  • Most bats apparently are promiscuous, but some South American species are known to form male-dominated harems.
  • Most Colorado bat mating occurs in autumn.
  • Sperm typically is stored by females throughout hibernation, sometimes up to seven months, in the uterus.
  • Within a few days of leaving the hibernaculum, females ovulate one egg, and sperm is released. Fertilization and implantation take place shortly thereafter.
  • Typically, females of a population form a maternity colony at a site different from the hibernaculum where breeding occurred.
  • Gestation usually lasts from 40 to 50 days and results in a single offspring, usually in the late spring in Colorado.
  • Hanging inverted, mothers grab the newborn young as it emerges from the birth canal.
  • Typically, the newborn grabs the abdominal fur of the mother with its hind feet and pulls to facilitate movement.
  • Other species of bats use gravity to assist the birthing, hanging by their thumbs, cradling the emerging young in their tails, and swinging them into the inter-femoral membrane, or uropatagium.
  • Infants usually begin nursing almost immediately after birth. There have been reports of females helping others with the birth of young.
  • Mothers of some species carry their suckling newborn young on feeding bouts.
  • It was long believed that a female bat returning from foraging would nurse any young of the colony as her own, but studies of maternity roosts of Brazilian free-tailed bats show clearly that females search for their own young until successful.
  • Young bats produce isolation calls, specialized high-frequency signatures that alert the mother to where her offspring is. A returning mother first identifies her youngster by its call, then “homes in” by recognizing its odor.
  • Parental care results in high survival of young for the first few weeks after birth.
  • A newborn’s wings grow rapidly.
  • Juveniles build their flight muscles by doing pushups and flapping while hanging stationary from the roost’s ceiling. After about three weeks of this activity, juveniles begin to attempt flights away from the maternity roost.
  • Mortality of young bats is very high during this developmental stage. Carnivores such as skunks, raccoons, coyotes and domestic cats and dogs kill wayward juveniles.
  • Predators such as snakes, hawks, and owls have been observed grabbing bats as they exit a roost.
  • Only about half the young born each year survive to adulthood.
  • If they survive the first few weeks of learning flight, juveniles reach adult size and flight ability the next month.
  • In late summer or fall, maternity colonies usually disperse with a mass exodus of individuals to the hibernaculum where the males await.
  • Female young of the year usually are reproductively active in the spring and return with other females to the maternity roost where they were born.
  • Females show high affinity for roost sites, but males, which are not reproductive their first year, are likely to disperse widely and may never return to their birthplace.

Bats Species Specifically Found in Colorado

Family Vespertilionidae:

Family Molossidae:


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Beneficial Bats 120 #C Park Street
Gypsum, CO 81637
Phone: (970) 524-5945
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