BIG BROWN BAT
Eptesicus fuscus
(Palisot de Beauvois, 1796)


ep-tes-i-cus fus-cus




Image © by Greg Sievert.
Image © by Greg Sievert.
Image © by Greg Sievert.
Image © by Greg Sievert.
Image © by Greg Sievert.

Description:
The big brown bat is one of the largest bats in Kansas with a large head, broad nose, and sparse vibrissae. The ears are short and rounded, the tragus is broad and blunt, the wings are short and broad, and the calcar is keeled. The pelage is soft, lax, and somewhat oily in texture. Pelage color depends on location, ranging from pinkish tan to rich brown dorsally, somewhat paler ventrally. Hairless areas of the face, ears, wings, and tail membrane are almost black. The dental formula is incisors 2/3, canine 1/1, premolars 1/2, molars 3/3.
The big brown bat superficially resembles several bats of the genera Myotis and Nycticeius that occur in Kansas. However, it can readily be distinguished from those bats by its much larger size. Moreover, Eptesicus has 2 upper incisors as opposed to just 1 in Nycticeius, and it has just 1 upper premolar as opposed to 2 in Myotis

Distribution:
The overall geographic distribution of the big brown bat extends from southern Canada through the entire United States and down through Middle America into South America. The big brown bat also is resident on some of the Bahama islands, Cuba, Hispaniola, Jamaica, Puerto Rico, Dominica, and Barbados. The species has been documented in all areas of Kansas except the southwestern counties and most of the Flint Hills. Whether or not the species actually occurs in those areas deserves investigation. Before settlement of Kansas, big brown bats likely were confined to caves, rock outcrops, and trees in eastern Kansas and to caves in the Gypsum Hills. Therefore, it probably did not occur in western Kansas before the arrival of settlers. Today, the big brown bat is commensal with man, and most of its largest colonies are in man-made structures (including churches, business buildings, houses, bridges, and outbuildings). Thus, this bat has benefited from the activities of man and today may be the most abundant species of bat in Kansas.
Based on the fossil record, Eptesicus fuscus was the most widespread bat in America during the Pleistocene. Fossils are known from more than 30 sites in Arizona, Arkansas, Florida, Georgia, Kentucky, Maryland, Missouri, Montana, New Mexico, Pennsylvania, Tennessee, Texas, Virginia, West Virginia, and Wyoming. Additionally, fossils are known from Mexico, the Bahamas, and Puerto Rico. 

(, Museum Voucher) (, Observation) (, Literature Record)
Open icons are questionable records; Click on a marker to view details.
  • Occurrence Summary:  
  • 1,171 Total Records 
  • 1,147 Museum Vouchers 
  • 24 Other Observations 
Some county occurrences indicated below may be too imprecise to map above.
County Breakdown: County Name (# occurrences):
Atchison (20); Barber (74); Barton (6); Cherokee (8); Cheyenne (8); Cloud (1); Coffey (1); Comanche (7); Cowley (8); Crawford (10); Decatur (1); Dickinson (1); Douglas (95); Ellis (189); Ellsworth (19); Franklin (1); Gove (41); Graham (8); Jackson (2); Jewell (24); Labette (3); Leavenworth (174); Lincoln (14); Logan (89); Lyon (12); Marshall (2); Miami (1); Mitchell (4); Montgomery (1); Nemaha (35); Ness (6); Norton (2); Osborne (32); Ottawa (29); Pawnee (8); Phillips (2); Pratt (3); Rawlins (63); Riley (3); Rooks (2); Rush (5); Russell (111); Saline (3); Scott (27); Shawnee (2); Smith (1); Thomas (2); Wilson (1); Woodson (2);

Natural History:
This is the bat most commonly found in houses in Kansas. They gain entry by way of chimneys, open windows, doors, ventilation ducts, or small cracks between ceilings and walls. In winter, as homes are heated, the bats become active and must search for a cooler location to continue hibernating. Under natural conditions these bats select dry places in caves, and it is for this reason that they are able to hibernate in dry buildings. Flying within a room presents no problem, and, although the bat can bite if captured, it is otherwise harmless and will not intentionally make contact with humans. Big brown bats commonly forage around city lights and over pools of water (including swimming pools and fish ponds). In flight, they follow a slow, straight course in open places but are capable of abrupt turns when encountering an insect. They may emit an audible chattering sound in flight. When big brown bats enter hibernation in late September or October, males usually precede the females. At the beginning of winter the bats already have accumulated a store of energy in the form of fat, and this stored energy maintains their metabolism throughout the winter. Body temperature becomes approximately the temperature of the hibernaculum, which must be cool enough to induce a low level of metabolism. If temperatures abruptly drop too low the bats can freeze, and if temperatures increase the bats will awaken and become active, thus depleting their fat stores. Except for females in maternity colonies, big brown bats are essentially solitary. Even in hibernation they prefer to be alone or in small, loosely aggregated groups. This nonmigratory species may awaken from hibernation in mid-winter and go out in search of a drink of water before resuming hibernation. It again awakens from hibernation in April, and it generally spends the summer near its winter hibernation site.
Adults may attain the following dimensions: total length 110-130 mm; length of tail 39-54 mm; length of hind foot 9-13 mm; length of ear 14-20 mm; weight 16.5-33 g. As in many other species of bats, females average larger than males. Weight is greater in autumn than in spring because of the layer of fat accumulated during summer for use as metabolic energy during winter.
Big brown bats are generalized feeders, although insects of the orders Coleoptera amd Hemiptera predominate. Most insects are captured and eaten on the wing or, if the insects are too large to manage in flight, the bat will consume them at a nearby night feeding roost.
The most common causes of mortality in this species are failure to store sufficient fat for hibernation, accidents, inclement weather, and predation. Documented predators include common grackles, American kestrels, various owls, long-tailed weasels, cats, rats, and bullfrogs. This bat stores agricultural chemicals in its tissues, and this may be a mortality factor. Finally, a low incidence of rabies occurs in this bat, and this species may be a vector of St. Louis encephalitis virus.
This is the bat most commonly found in houses in Kansas. They gain entry by way of chimneys, open windows, doors, ventilation ducts, or small cracks between ceilings and walls. In winter, as homes are heated, the bats become active and must search for a cooler location to continue hibernating. Under natural conditions these bats select dry places in caves, and it is for this reason that they are able to hibernate in dry buildings. Flying within a room presents no problem, and, although the bat can bite if captured, it is otherwise harmless and will not intentionally make contact with humans. Big brown bats commonly forage around city lights and over pools of water (including swimming pools and fish ponds). In flight, they follow a slow, straight course in open places but are capable of abrupt turns when encountering an insect. They may emit an audible chattering sound in flight. When big brown bats enter hibernation in late September or October, males usually precede the females. At the beginning of winter the bats already have accumulated a store of energy in the form of fat, and this stored energy maintains their metabolism throughout the winter. Body temperature becomes approximately the temperature of the hibernaculum, which must be cool enough to induce a low level of metabolism. If temperatures abruptly drop too low the bats can freeze, and if temperatures increase the bats will awaken and become active, thus depleting their fat stores. Except for females in maternity colonies, big brown bats are essentially solitary. Even in hibernation they prefer to be alone or in small, loosely aggregated groups. This nonmigratory species may awaken from hibernation in mid-winter and go out in search of a drink of water before resuming hibernation. It again awakens from hibernation in April, and it generally spends the summer near its winter hibernation site.
Adults may attain the following dimensions: total length 110-130 mm; length of tail 39-54 mm; length of hind foot 9-13 mm; length of ear 14-20 mm; weight 16.5-33 g. As in many other species of bats, females average larger than males. Weight is greater in autumn than in spring because of the layer of fat accumulated during summer for use as metabolic energy during winter.
Big brown bats are generalized feeders, although insects of the orders Coleoptera amd Hemiptera predominate. Most insects are captured and eaten on the wing or, if the insects are too large to manage in flight, the bat will consume them at a nearby night feeding roost.
The most common causes of mortality in this species are failure to store sufficient fat for hibernation, accidents, inclement weather, and predation. Documented predators include common grackles, American kestrels, various owls, long-tailed weasels, cats, rats, and bullfrogs. This bat stores agricultural chemicals in its tissues, and this may be a mortality factor. Finally, a low incidence of rabies occurs in this bat, and this species may be a vector of St. Louis encephalitis virus.
Copulation occurs before entry into hibernation in autumn and also during periods of arousal in winter and spring. Fertilization and implantation occur after ovulation, typically in the first week of April. In early April, females leave hibernation sites and form nursery colonies. Young are born between the end of May and mid-June. Interestingly, big brown bats in Colorado and farther west have just 1 pup per year, whereas bats in the East have 2 pups per year. The only published study in Kansas, based on work done in Russell, revealed that our big brown bats produce 2 pups per year. Young are capable of flight 3 or 4 weeks after birth and are fully grown at about 70 days of age.

Occurrence Activity:
Remarks:
All populations of this species in Kansas evidently pertain to the subspecies Eptesicus fuscus fuscus. Another subspecies, E. f. pallidus, occurs to the west and north of Kansas but evidently does not occur in our state.

Bibliography:
1936 Engels, W. L. Distribution of races of the brown bat (Eptesicus) in western North America. American Midl. Nat., 17:653-660. ():
1952 Cockrum, E. L. Mammals of Kansas. Univ. Kansas Publ. Mus. Nat. Hist. 7:1-303. ():
1966 Phillips, G. L. Ecology of the big brown bat (Chiroptera: Vespertilionidae) in northeastern Kansas. American Midl. Nat., 75:168-198. ():
1967 Jones, J. K. Jr., E. D. Fleharty, and P. B. Dunnigan The distributional status of bats in Kansas. Univ. Kansas Mus. Nat. Hist. Misc. Publ., 46:1-33. ():
1986 Choate, J. R., J. W. Dragoo, J. K. Jones, Jr., and J. A. Howard Subspecific status of the big brown bat, Eptesicus fuscus, in Kansas Prairie Nat. 18(1):43-51
1990 Kurta, A., and R. H. Baker Eptesicus fuscus Mammalian Species 356():1-10
2000 Sparks, D. W., and J. R. Choate Distribution, natural history, conservation status, and biogeography of bats in Kansas Pages 173-228 in Reflections of a Naturalist: Papers Honoring Professor Eugene D. Fleharty Fort Hays State University, Hays, KS. pp.
2007 Brack, V., Jr., L. W. Robbins, and C. R. Davis Bats of Fort Leavenworth Military Reservation and nearby areas of eastern Kansas and western Missouri Transactions of the Kansas Academy of Science 110(1-2):73-82
2008 Timm, R. M., G. R. Pisani, J. R. Choate, N. A. Slade, G. A. Kaufman, and D. W. Kaufman http://www.ku.edu/~mammals, . pp.
Account Last Updated:
8/21/2018 7:53:35 PM


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