Lasiurus cinereus (Hoary Bat)
Written by Nicole deJongh (Mammalogy Lab--Fall 2003)

Edited by Karah Gallagher and Jennifer Bailey

The Hoary bat is part of the family vespertilionidae or common bats.  Of all  North American bats, L. cinereus  is the most widespread.  It is a migratory species that ranges from just below the Canadian tree line to Central America to Brazil, Argentina, and Chile in South America (Shump and Shump 1982).  Typically, they winter in southern California, southeastern United States, Mexico, and Guatemala (Shump and Shump 1982) and summer in Canada (Barbour and Davis 1969).

Physical Characteristics:

L. cinereus is a relatively large bat with an average weight of 30g (Rolseth et al.1994).  Females are somewhat larger than males by approximately 3.9% (Koehler and Barclay 2000).  Adult pelage is a mix of dark brown and gray tinged with white.  The term Lasiurus means "hairy tail" and cinereus means "grayish" or "ash". Facial characteristics of L. cinereus include short rounded ears and a short broad tragus. (Barbour and Davis 1969).  Reported measurements include: total body length 134.5mm, tail length 57.5mm, tibia length 23.2mm, hind foot length 10mm, forearm length 50.2mm, thumb length 10.6mm, longest finger length 107mm, ear length 18mm, tragus length 9mm. (Miller 1897).  L. cinereus has a wingspan of 342mm-424mm and generally high wing loading ranging from .093g/cm²-.15g/cm² (Farney and Fleharty 1969).  This high wing loading makes them rapid fliers and relatively unmanuverable (Barclay 1985).  In a flight speed test, L. cinereus was found to tire less quickly than most bats and its highest speed was clocked at 13.2 mph (Hayward and Davis 1964).  However, this does not mean that this is the animals actual top speed.

Natural History:

Food Habits: Little is known about the food habits of L. cinereus.  From the manner in which they feed they appear to have a primary diet of moths (Black 1972).  When feeding, the bat will bit the thorax of the moth leaving the wings to fall to the ground.  The chitinous scales of the moth can be found in fecal pellets (Black 1972).  Though they are a solitary species, their foraging zones do overlap with Eptesicus fuscus, Lasiurus borealis, and other members of its own species (Black 1972, Hickey et al. 1996).  Small differences in what the bats feed on and the way they feed helps to reduce competition.  It is possible that the echo given off by moths trigger a negative response in E. fuscus and a positive response in L. cinereus (Black 1972).  Though L. cinereus and L. borealis are sympatric and feed on the same size range of moths, L. cinereus feeds very heavily on larger moths.  This may be because L. cenereus emits a lower frequency sound that is best at detecting insects from long range  (Hickey et al. 1996).  Thus, larger insects are the target.  Differences also exist between young and adult L. cinereus.  With calls at 20kHz-16kHz (lower than many aerial insectivorous bats) detection of small insects is poor (Barclay 1985).  Young have lower wing loading and higher frequency calls so  are more suited to feed on small insects (Rolseth et al. 1994).

 Reproduction:  L. cinereus typically have 2 young per litter while most bats only have one (Koehler and Barclay 2000).  Mating occurs during or before the fall migration and delayed implantation takes place  (Barbour and Davis 1969).  During spring migration, females and males segregate and are apart for most of the warm months (Findley and Jones 1964).  The females arrive in Canada where most give birth to twins in early June (Bouchard et al. 2001).  Distribution of L. cinereus changes during breeding.  A study shows that females with young are less common in high altitudes than females without young or males (Barclay 1991).  By selecting for elevations with warmer habitats, females are able to avoid long wintering migrations (Barclay 1991) and can take advantage of high insect densities before hibernation (Cryan et al. 2000).  Koehler and Barclay (2000) found that because L. cinereus roosts in foliage, females and young are exposed to external ambient conditions throughout the season.  Young in torpor will have slower growth rates, and twins will have slower growth rates than single young (Koehler and Barclay 2000).  Therefore, L. cinereus young generally have a slower growth rate than other bat species.

 There are two mechanisms that provide safety following birth.  One is well developed thumbs and feet for grasping the mother and the other is the delayed placental detachment, which functions as a safety line if the newborn should fall (Bogan 1972).  The newborn are covered with fine silvery hair on the dorsum of the head, shoulders, uropatagium, and feet.  The eyes are closed and the ears pressed closely to the head (Bogan 1972).

 Behavior: L. cinereus is a very solitary species and only associates with other species in the summer while foraging. (Rolseth et al. 1994).  It generally does not survive well on its own  in captivity.  L. cinereus are typically intolerant to handling and will react aggressively except in late pregnancy.  This change in behavior is valuable for two reasons.  It allows the female to tolerate the physical contact of her young, and also causes her to remain hidden during potential threats instead of acting aggressively and risking the life of her young. ( Bogan 1972).  There have been numerous reports of unusual behavior by L. cinereus.  An observation was made on September 29, 1947 in western Kern County, California at the base of a cliff.  A male Hoary bat was seen pursuing a smaller bat (Orr 1950).  This is most unusual behavior and an unusual location to make such a sighting.  Another account shows how aggressive L. cinereus can be.  A bat with a small pepistrellus did not loosen its grasp even after being handled (Bishop 1947).  One last account showed unusual feeding habits of a bat hibernating on a house in Indiana.  The bat had significant amounts of green vegetation in its stomach along with a snake skin (Whitaker 1967).

  Habitat:  The two main factors that insectivorous bats select for are prey availability and roost sites (Kalcounis et al 1999).  L. cinereus roosts primarily in foliage (Jung et al. 1999) 3m-5m above ground in trees such as elm, black cherry, plum, box elder, and osage orange (Constantine 1966).  Old growth forests are important for all bat species including L. cinereus (Jung et al. 1999).  These forests have the canopies of young forests and the super canopies of old forests.  Old forests provide less cluttered areas, so that heavier less agile bat species such as L cinereus can forage in (Jung et al. 1999).  A study in Canada shows that the average number of calls per night of L. cinereus are higher above the canopy than below the canopy (Kalcounis et al. 1999).  It can be expected that L. cinereus will be more abundant in more open areas of forests.

Currently there is no economic importance of L. cinereus except for protecting land that is important to the species so that future generations may see and learn about it.

Conservation Status:

The Hawaian subspecies L. cinereus semotus is at risk of endangerment.  Because it is endemic to the Island of Hawaii it is not as widespread as other subspecies.  Unlike other subspecies, it remains in one territory year round.  It also feeds on many other insects than just moths (Shump and Shump 1982). 

Studies have shown that urban wildlife refuges can provied important areas for bats.  Maintaining land by creating gaps in new growth forests and creating edge habitats, particularly around water, will provide more favorable roosting and foraging sites (Everette et al. 2001). 

References:

Barbour, R. W., and W. H. Davis.1969.  Bats of America. University Press of Kentucky, Lexington, Kentucky 1-286.

Barclay, R. M. R. 1985.  Long- versus short-range foraging strategies of hoary (Lasiurus cinereus) and silver-haired (Lasionycteris noctivagans) bats and the consequences for prey selection. Canadian Journal of Zoology 64:2700-2705.

Barclay, R. M. R. 1991.  Population structure of temperate zone insectivorous bats in relation to foraging behavior and energy demand.  The Journal of Animal Ecology 60:165-178.

Bishop, Sherman C. 1947.  Curious behavior of a hoary bat. Journal of Mammalogy 28(3):293-294.

Black, Hal L. 1972.  Differential exploitation of moths by the bats Eptesicus fuscus and Lasiurus cinereus. Journal of Mammalogy 53(3):598-601

Bogan, Michael A. 1972.  Observations on parturition and development in the hoary bat, Lasiurus cinereus. Journal of Mammalogy 53(3):611-614.

Bouchard, Sylvie, Joanna Zigouris, and M. Brock Fenton. 2001.  Autumn mating and likely resorption of an embryo by a hoary bat, Lasiurus cinereus (chiroptera: vespertilionidae). American Midland Naturalist 145:210-212.

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

Cryan, Paul M., Michael A. Bogan, and J. Scott Altenbach. 2000.  Effect of elevation on distribution of female bats in the Black Hills, South Dakota. Journal of Mammalogy 81(3):719-725.

Everette, Lance A., Thomas J. o'Shea, Laura E. Ellison, Laura A. Stone, and James L. McCance. 2001.  Bat use of a high-plains urban wildlife refuge. Wildlife Society Bulletin 29(3):967-973.

Farney, John and Eugene D. Fleharty. 1969.  Aspect ratio, loading, wing span, and membrane areas of bats. Journal of Mammalogy 50(2):362-367.

Findley, James S., and Clyde Jones. 1964.  Seasonal distribution of the hoary bat. Journal of Mammalogy 45(3):461-470.

Hayward, Bruce, and Russel Davis. 1964.  Flight speeds in Western bats. Journal of Mammalogy 45(2):236-242.

Hickey, Brian M., Lalita Acharya, and Shannon Pennington. 1996.  Resource partitioning by two species of vespertilionid bats (Lasiurus cinereus and Lasiurus borealis) feeding around street lights. Journal of Mammalogy 77 (2):325-334.

Jung, Thomas S., Ian D. Thompson, Rodger D. Titman, Andrew P. Applejohn. 1999.  Habitat selection by forest bats in relation to mixed-wood stand types and structure in central Ontario. Journal of Wildlife Management 63 (4):1306-1319.

Kalcounis, M. C., K. A. Hobson, R. M. Brigham, and K. R. Hecker.1999.  Bat activity in the boreal forest: importance of stand type and vertical strata. Journal of Mammalogy 80(2):673-682.

Koehler, Catherine E., and Robert M. R. Barclay. 2000.  Post-natal growth and breeding biology of the hoary bat (Lasiurus cinereus). Journal of Mammalogy 81(1):234-244.

Miller, G. S., Jr. 1897. Revision of the North American bats of the family Vespertilionidae. North American Fauna 13:1-135.

Orr, Robert T. 1950.  Unusual behavior and occurrence of a hoary bat. Journal of Mammalogy 31(4):456-457.

Rolseth, Scott L., Catherine E. Koehler, and Robert M. R. Barclay. 1994.  Differences in the diets of juvenile and adult hoary bats, Lasiurus cinereus. Journal of Mammalogy 75 (2):394-398.

Shump, Karl A. Jr. and Ann U. Shump. 1982.  Lasiurus cinereus. Mammalian Species 185:1-5.

Whitaker, J. O., Jr. 1967.  Hoary bat apparently hibernating in Indiana. Journal of Mammalogy 48:663.