Lasiurus borealis
(Muller, 1776)

laz-E-ur-us bor-E-al-us

Photo by Bob Gress.

Lasiurus borealis is a small bat with the dorsum colored brick red to rusty red washed with white and the venter slightly paler. Males are redder than females. A buffy white patch is located on the anterior surface of each shoulder. The tail is long and the interfemoral membrane is well furred. Red bats can be distinguished from other Kansas bats by their red color, furred interfemoral membrane, and long tail. No other bat in the state shares these features.

Adults may attain the following dimensions: total length 103-124 mm; length of tail 43-60 mm; length of hind foot 8-10 mm; length of ear 10-14 mm; weight 6-14 g.

The dental formula is incisors 1/3, canine 1/1, premolars 2/2, molars 3/3.

Fossils of Lasionycteris have been found in Pleistocene sites in Texas and Wyoming.The overall range of the red bat includes the eastern United States, southernmost Canada, and northeasterm Mexico west to near the continental divide. However, during winter this migratory species occurs mainly in the southeastern United States and northeastern Mexico. Red bats presumably arrive in Kansas in April and depart in September, but see below. During summer, they can be found in Kansas wherever there are trees that are suitable for roosting.
Late Pleistocene specimens of this species have been found in local faunas in Florida, Missouri, Virginia, and West Virginia.

(, Museum Voucher) (, Observation) (, Literature Record)
Open icons are questionable records; Click on a marker to view details.
  • Occurrence Summary:  
  • 535 Total Records 
  • 520 Museum Vouchers 
  • 15 Other Observations 
Some county occurrences indicated below may be too imprecise to map above.
County Breakdown: County Name (# occurrences):
Allen (1); Anderson (2); Atchison (2); Barber (10); Barton (5); Bourbon (8); Butler (1); Chautauqua (1); Cherokee (9); Coffey (1); Comanche (1); Cowley (4); Crawford (15); Doniphan (4); Douglas (210); Edwards (2); Elk (1); Ellis (33); Ellsworth (1); Franklin (4); Geary (1); Graham (1); Grant (1); Gray (2); Greenwood (64); Hamilton (2); Harvey (4); Jackson (4); Jefferson (1); Jewell (2); Johnson (1); Kearney (1); Kiowa (2); Labette (1); Leavenworth (7); Linn (1); Lyon (35); Marshall (2); McPherson (3); Meade (6); Montgomery (8); Morton (2); Neosho (1); Osborne (1); Pawnee (4); Phillips (1); Pottawatomie (1); Rice (1); Riley (9); Rooks (3); Rush (2); Russell (1); Saline (1); Scott (1); Sedgwick (13); Seward (1); Shawnee (7); Smith (4); Stafford (2); Stanton (4); Trego (1); Washington (4); Woodson (6); Wyandotte (1);

Natural History:
Red bats are considered "tree bats" in that they roost almost exclusively in trees (or occasionally in shrubs or even on the underside of leaves of the sunflower plant). Favored trees include elm, box elder, wild plum, and silver maple, but other tree species are used based on availability. Roosts provide cover from above and the side, but they are open below. This enables this narrow-winged bat to drop from the roost and pick up enough speed for flight. Although well camouflaged, eastern red bats sometimes are seen within reach of the ground. Also, they sometimes are "picked" in the mistaken assumption that they are a fruit. They generally are solitary, but several may roost together on rare occasions and it is assumed that the bats communicate with each other. They are regarded as a strongly migratory bat, and dogma assumes that the furred membranes of this species provide warmth during cold spells before or during migration. However, studies conducted in Missouri demonstrated that some eastern red bats remain there year-round, roosting in trees when the temperature is moderate and dropping to the ground and crawling beneath leaf litter during cold snaps. Furthermore, the bats somehow find insects on which to feed throughout the winter. Eastern red bats that migrate tend to do so in groups that are segregated by gender.

Food consists of flying insects. Foraging begins between 1 and 2 h ours after sunset. After getting a drink from a nearby water source, eastern red bats begin to forage above the tree tops in a relatively slow, erratic flight. Later in the evening, they fly lower and more rapidly. In towns, they are attracted to street lights to feed on moths and may be heard emitting a sharp chirp, chatter, or squeal.
The greatest threat to the eastern red bat is the Blue Jay. Other predators that prey on this bat include opossums, hawks, and owls. Spring and summer storms often blow females with their young from trees. Because these bats must climb up on something a sufficient distance to dive off and obtain speed for flight, they and their young are especially vulnerable to cats and perhaps dogs until the females can retrieve their young and return to the roost.

Both males and females are solitary. Copulation is initiated in flight in August and September. Fertilization occurs in the spring, and the actual gestation period varies from 80 to 90 days. From 1 to 5 blind and hairless young (usually 3 or 4) are born in mid-June. This is more young per litter than in any other bat. The young cling to the underparts of the female with their hind feet, teeth, and thumb claws. The young are left hanging on limbs of trees while the female forages, but if the family is disturbed she may carry the young to a new roost. The young nurse from the four nipples on the female. At about 3 to 6 weeks of age the young are weaned, and they can fly by the age of 4 to 6 weeks.

Occurrence Activity:
A relatively high incidence of rabies (about 7%) has been found in this species. Persons should not handle eastern red bats that blow out of trees, and they should keep their cats and dogs away until the bats manage to return to the roost.
Based on genetic studies, Lasiurus borealis recently was split into two species. According to this classification, Lasiurus borealis contains no subspecies and, therefore, is monotypic.

1952 Cockrum, E. L. Mammals of Kansas. Univ. Kansas Publ. Mus. Nat. Hist. 7:1-303. ():
1954 Rainey, D. G., and H. J. Stains Early seasonal record of the red bat in Kansas. Trans. Kansas Acad. Sci., 57:85. ():
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. ():
1982 Shump, K. A., Jr., and A. U. Shump Lasiurus borealis Mammalian Species 183():1-6
1983 Jones, J. K., Jr., D. M. Armstrong, R. S. Hoffmann, and C. Jones University of Nebraska Press, Lincoln, NE. 1-379pp.
1996 Sparks, D.W. and J.R. Choate New distributional records for mammals in Kansas Prairie Naturalist 27(4):185-192
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.
2003 Cryan, P. M. Seasonal distribution of migratory tree bats (Lasiurus and Lasionycteris) in North America ():
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 7:54:15 PM

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