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red bat

Lasiurus borealis

What do they look like?

Red bats are medium sized bats having a total length of 93 to 117 mm. Body length is approximately 40 to 50 mm and weight ranges between 7 to 13 g. The hindfoot length is 6 to 11 mm. Height of the ear is 8 to 13 mm. Length of the forearm varies between 36 and 46 mm.

The coat varies in color from a brick red to a yellowish red. The fur is white at the tips, giving these bats a frosted appearance. In general, female bats appear more frosted compared to males, and males have a redder color than females. There is no difference in size between males and females. The tail membrane is thickly furred on the upper side and helps to keep these bats warm in cold weather. Red bats have 32 teeth.

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • Range mass
    7 to 13 g
    0.25 to 0.46 oz
  • Range length
    93 to 117 mm
    3.66 to 4.61 in

Where do they live?

Red bats are widely distributed in forested regions, occurring from southern Canada through Central America and into Chile and Argentina. Red bats migrate to warmer regions during winter.

What kind of habitat do they need?

Red bats are fast flying bats that live throughout the Americas. They tend to choose habitats that have few humans and are rare in cities and towns.

How do they reproduce?

An incomplete account of a red bat mating in flight was made in 1947. A bat biologist was fly fishing and watched as he saw what looked like a single bat tumble onto the bank. The biologist inspected with his flashlight, and saw what he originally thought was a female bat with young clinging to her. Under closer inspection the biologist saw that a male had clasped itself to the back of the female therefore making it impossible for either to fly. It seemed as if the male red bat had attached itself to the female in mid-flight. The male bat seemed to hold his position by hooking his claw over the female's wing.

Mating takes place in flight and usually occurs in August or September. Female red bats store the males' sperm, and they do not get pregnant until the spring, usually March or April. Female red bats have four mammary glands while most other bats have two. Female red bats give birth to one litter of twins each year, unlike most bats which give birth to single young. Newborn bats are hairless and weigh approximately 1.5 g. The young learn to fly at about five weeks old.

  • How often does reproduction occur?
    Red bats breed once each year.
  • Breeding season
    Mating occurs in August or September.
  • Range number of offspring
    1 to 4
  • Average number of offspring
  • Range gestation period
    80 to 90 days
  • Average weaning age
    38 days
  • Average time to independence
    5 weeks

Like all mammals, female red bats nurse their young until the young are able to fend for themselves. It takes young red bats about five weeks to learn how to fly and find food.

  • Parental Investment
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

How do they behave?

Red bats are migratory, arriving in the northern climates in mid-April and leaving in late October. There are records of bats hibernating in the northern parts of their range, but they typically migrate to warmer regions. When red bats hibernate they choose hollow trees. Their body temperatures drop to just above freezing and they cannot survive long periods of below freezing temperatures. They live off their fat reserves while hibernating and they may lose up to 25% of their pre-hibernation body weight by spring.

Red bats choose roosting sites in thick foliage. They may be seen hanging from branches or leaves but their coloration helps to camouflage them from predators. Their red coat is particularly helpful at camouflaging them in sycamore, oaks, elm, and box elder trees and they seem to prefer these trees as roost sites. Sites that have been used as roosting areas range from 2 to 40 feet off the ground. The roosting sites of solitary bats have not been as well studied as those of more social bats. Some field workers believe that red bats defend feeding territories.

How do they communicate with each other?

Red bats use echolocation to locate prey.

What do they eat?

Red bats are insectivorous. They capture insects while flying like many other insectivorous bats.

Red bats often hunt for insects around lights. Hunting for food begins at dusk and the bat hunts within 500 m of a light source. Generally there is only one peak feeding time during the night, but there are records of these bats searching for food throughout the night. Red bats eat many different kinds of insects: moths, beetles, plant-hoppers, ants, flies, and others.

Red bats swoop through a concentration of potential prey, fixing on a target within 5 to 10 m. They attack insects, on average, every thirty seconds and are successful fourty percent of the time. If a bat is stalking a moth using echolocation the moth can hear this and will try to flee the attack by diving. The bat will follow the moth into a steep dive and often will pull away within inches of the ground. Humans observing this predator-prey interaction only see the bat and not the fleeing moth and may believe that the bat is acting aggressively towards them.

When hunting, red bats hold their heads and bodies in a distinct way. It has been said that if you look at a rural street light and see a bat dipping and diving, that you are most likely seeing a red bat.

  • Animal Foods
  • insects

What eats them and how do they avoid being eaten?

Predators of red bats include birds of prey and opossums. Humans and human constructions have also taken their toll on red bats. They may get caught on barbed wire, trapped on oily road surfaces, hit by cars, or they may fly into lighthouses.

Red bats avoid predators through the use of camouflage.

  • These animal colors help protect them
  • cryptic

What roles do they have in the ecosystem?

Red bats play an important ecosystem role as insect consumers.

Do they cause problems?

Unfortunately some people view red bats, along with all other bats, as pests. However, red bats do not negatively affect humans.

How do they interact with us?

Red bats rarely invade homes. Red bats keep insect populations down.

  • Ways that people benefit from these animals:
  • controls pest population

Are they endangered?

Red bats are secure over most of their range and are not considered threatened.

Temperate North American bats are now threatened by a fungal disease called “white-nose syndrome.” This disease has devastated eastern North American bat populations at hibernation sites since 2007. The fungus, Geomyces destructans, grows best in cold, humid conditions that are typical of many bat hibernacula. The fungus grows on, and in some cases invades, the bodies of hibernating bats and seems to result in disturbance from hibernation, causing a debilitating loss of important metabolic resources and mass deaths. Mortality rates at some hibernation sites have been as high as 90%. While there are currently no reports of Lasiurus borealis mortalities as a result of white-nose syndrome, the disease continues to expand its range in North America. (Cryan, 2010; National Park Service, Wildlife Health Center, 2010)


Allison Poor (editor), University of Michigan-Ann Arbor.

Phil Myers (author), Museum of Zoology, University of Michigan-Ann Arbor, Jani Hatchett (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.


Altringham, J. 1996. Bats biology and behaviour. Oxford: Oxford University Press.

Baker, `. 1983. Michigan Mammals. Lansing: Michigan State University Press.

Constantine, D. 1966. Ecological observation of lasiurine bats in Iowa. Journal of Mammalogy, 47: 34-41.

Cryan, P. 2010. "White-nose syndrome threatens the survival of hibernating bats in North America" (On-line). U.S. Geological Survey, Fort Collins Science Center. Accessed September 16, 2010 at

Davis, W., W. Lidicker. May 1956. Winter range of the red bat, Lasiurus borealis. Journal of Mammalogy, 37: 280-281.

Fenton, B. 1985. Communication in the Chiroptera. Bloomington: Indiana University Press.

Fenton, B. 1983. Just Bats. Toronto: University of Toronto Press.

Hickey, B., L. Acharya, S. Pennington. May 1996. Resource partitioning by two species of vespertilionis bats (Laiurus cinereus and Lasiurus borealis) feeding around street light. Journal of Mammology, 77: 325-334.

Hickey, B., A. Neilson. 1995. Relative activity and occurence of bats in Southwesten Ontario as determined by monitoring with bat detectors. The Canadia Field-Naturalist, 109: 413-417.

National Park Service, Wildlife Health Center, 2010. "White-nose syndrome" (On-line). National Park Service, Wildlife Health. Accessed September 16, 2010 at

Perston, R. 1964. Silently, By Night. New York: McGraw and Hill.

Schober, W., E. Grimmberger. 1997. The bats of Europe and North America. Dallas: T.F.H. Publicaitons, Inc. 1997.

Slaughter, B., D. Walton. 1970. About Bats a Chiropteran biology synposium. Dallas: Southwestern Methodist University Press.

Stuewer, F. 1948. A record of red bats mating. Journal of Mammalogy, 29 (2): 180-181.

Wilson, N. 1965. Red bats attracted to insect light traps. Journal of Mammalogy, 46 (4): 704-705.

University of Michigan Museum of ZoologyNational Science Foundation

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Myers, P. and J. Hatchett 2000. "Lasiurus borealis" (On-line), Animal Diversity Web. Accessed May 21, 2024 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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