Bats - New York State Department of Health .simplify getting bats out. Quality bat-proofing permanently

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    Cooperative Extension DivisionInstitute of Agriculture and Natural ResourcesUniversity of Nebraska - Lincoln

    United States Department of AgricultureAnimal and Plant Health Inspection ServiceAnimal Damage Control

    Great Plains Agricultural CouncilWildlife Committee

    Damage Prevention andControl Methods


    Polypropylene netting checkvalvessimplify getting bats out.

    Quality bat-proofing permanentlyexcludes bats.

    Initiate control before young are bornor after they are able to fly.


    Naphthalene: limited efficacy.


    Air drafts/ventilation.

    Ultrasonic devices: not effective.

    Sticky deterrents: limited efficacy.


    None are registered.


    Available, but unnecessarilycomplicated compared to exclusionand bat-proofing.

    Other Methods

    Sanitation and cleanup.

    Artificial roosts.

    Important Note: This document is included for information it provides pertinent to bat behavior, exclusion techniques, damage identification, prevention and control measures. However, pages D14 - D18 contain information about rabies and removal of bats from homes that is incomplete with regard to current public health recommendations. For current information see

    Guidelines for Managing Bats and Risk of Rabies Transmission at:

    Arthur M. GreenhallResearch AssociateDepartment of MammalogyAmerican Museum of Natural HistoryNew York, New York 10024

    Stephen C. FrantzVertebrate Vector SpecialistWadsworth Center for Laboratoriesand ResearchNew York State Department of HealthAlbany, New York 12201-0509

    Fig. 1. Little brown bat, Myotis lucifugus

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    Fig. 2. Little brown bat, Myotis lucifugus

    Fig. 3. Big brown bat, Eptesicus fuscus


    Conservation and Public Education

    Despite their ecological value, bats arerelentlessly and unjustifiably perse-cuted. Bats are often killed becausethey live near people who needlesslyfear them. These actions emphasize theneed to educate the public on the rea-sons for bat conservation and why it isimportant to use safe, nondestructivemethods to alleviate conflicts betweenpeople and bats. General sources ofinformation on bats include statesCooperative Extension Services, uni-versities, government environmentalconservation and health departments,and Bat Conservation International(Austin, Texas). Except where controlis necessary, bats should be appreci-ated from a distance and not dis-turbed.

    Identification and Range

    Bats, the only mammals that truly fly,belong to the order Chiroptera. Theirability to fly, their secretiveness, andtheir nocturnal habits have contributedto bat folklore, superstition, and fear.They are worldwide in distributionand include about 900 species, secondin number only to Rodentia (therodents) among the mammals.

    Among the 40 species of bats foundnorth of Mexico, only a few causeproblems for humans (note that vam-pire bats are not found in the UnitedStates and Canada). Bats congregatingin groups are called colonial bats;those that live a lone existence areknown as solitary bats.

    The colonial species most often en-countered in and around humanbuildings in the United States are thelittle brown bat, (Myotis lucifugus, Fig.2), the big brown bat (Eptesicus fuscus,Fig. 3), the Mexican free-tailed bat(Tadarida brasiliensis, Fig. 4), the pallidbat (Antrozous pallidus), the Yumamyotis (Myotis yumanensis), and theevening bat (Nycticeius humeralis).

    Solitary bats typically roost in tree foli-age or under bark, but occasionally arefound associated with buildings, someonly as transients during migration.

  • Fig. 5. Anatomy of a typical bat




    Upper arm





    Fourth finger

    Fifth finger

    Wing membrane





    Fig. 4. Mexican free-tailed bat, Tadarida brasiliensis

    These include Keens bat (Myotiskeenii), the red bat (Lasiurus borealis),the silver-haired bat (Lasionycterisnoctivagans), and the hoary bat(Lasiurus cinereus). Excellent illustra-tions of all bats discussed herein can befound in Barbour and Davis (1979),Tuttle (1988), Geluso et al. (1987), andHarvey (1986).

    Several species of bats have beenincluded here, with significant inter-specific differences that need to beclarified if well-planned, comprehen-sive management strategies are to bedeveloped. Any problems caused bybats are limited to species distribution;thus animal damage control personnelneed not be concerned with every spe-cies.

    Colonial and solitary bats have obvi-ous differences that serve to separatethe species into groups (refer to Fig. 5).Much of the descriptive material thatfollows is adapted from Barbour andDavis (1979).


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    Colonial Bats

    Little brown bat (Myotis lucifugus)


    forearm 1.34 to 1.61 inches (3.4 to4.1 cm)

    wingspan 9.02 to 10.59 inches (22.9to 26.9 cm)

    ears 0.55 to 0.63 inches (1.4 to 1.6cm)

    foot approximately 0.39 inches (1.0cm); long hairs on toes extend be-yond claws.

    Distribution (Fig. 6a)


    Pale tan through reddish brown todark brown, depending on geo-graphic location. The species is arich dark brown in the easternUnited States and most of the westcoast. Fur is glossy and sleek.

    Confusion may occur with a few otherhouse bat species. In the East, itmay be confused with Keens bat(M. keenii), which has longer ears[0.69 to 0.75 inches (1.7 to 1.9 cm)]and a longer, more pointed tragus(the appendage at the base of theear). In the West, it resembles theYuma myotis (M. yumanensis),which has dull fur and is usuallysmaller. However, the Yuma myotisand little brown may be indistin-guishable in some parts of thenorthwestern United States wherethey may hybridize.


    This is one of the most common batsfound in and near buildings, oftenlocated near a body of water wherethey forage for insect prey. Summercolonies are very gregarious, com-monly roosting in dark, hot atticsand associated roof spaces wherematernity colonies may includehundreds to a few thousand indi-viduals. Colonies may also formbeneath shingles and siding, in treehollows, beneath bridges, and incaves. Litter size is 1 in the North-east; twins occasionally occur insome other areas. The roost is oftenshared with the big brown bat (E.fuscus) though the latter is less toler-

    ant of high temperatures; M. keeniimay also share the same site. Sepa-rate groups of males tend to besmaller and choose cooler roostswithin attics, behind shutters, undertree bark, in rock crevices, andwithin caves.

    In the winter, little brown bats in theeastern part of their range abandonbuildings to hibernate in caves andmines. Such hibernacula may benear summer roosts or up to a fewhundred miles (km) away. Little isknown of the winter habits of M.lucifugus in the western UnitedStates.

    The life span of little brown bats hasbeen established to be as great as 31years. The average life expectancy,however, is probably limited to onlya few years.

    Big brown bat (Eptesicus fuscus)


    forearm 1.65 to 2.01 inches (4.2 to5.1 cm)

    wingspan 12.80 to 13.78 inches (32.5to 35.0 cm)

    ears with rounded tragus

    Distribution (Fig. 6b)


    From reddish brown, copper colored,to a dark brown depending on geo-graphic location. This is a large batwithout distinctive markings.

    Confusion may occur with the eveningbat (Nycticeius humeralis) though thelatter is much smaller.


    This hardy, rather sedentary speciesappears to favor buildings for roost-ing. Summer maternity coloniesmay include a dozen or so and upto a few hundred individuals, roost-ing behind chimneys, in enclosedeaves, in hollow walls, attics, barns,and behind shutters and unusedsliding doors. They also form colo-nies in rock crevices, beneathbridges, in hollow trees, and underloose bark. Litter size is 2 in the Eastto the Great Plains; from theRockies westward 1 young is born.

    E. fuscus frequently shares roostswith M. lucifugus in the East, andwith M. yumanensis, Taderida, andAntrozous in the West. Males typi-cally roost in smaller groups oralone during the summer.

    The big brown bat is one of the mostwidely distributed of bats in theUnited States and is probably famil-iar to more people than any otherspecies. This is partially due to itslarge, easy-to-observe size, but alsoto its ability to overwinter in build-ings (attics, wall spaces, and base-ments). Its close proximity tohumans, coupled with its tendencyto move about when temperatureshifts occur, often brings this batinto human living quarters andbasements in summer and winter.Big browns also hibernate in caves,mines, storm sewers, burial vaults,and other underground harborage.While E. fuscus will apparentlytravel as far as 150 miles (241 km) tohibernacula, the winter quarters ofthe bulk of this species are largelyunknown.

    Big brown bats may live as long as 18years.

    Mexican free-tailed bat (Tadaridabrasiliensis)


    forearm 1.42 to 1.81 inches (3.6 to4.6 cm)

    wingspan 11.42 to 12.80 inches (29.0to 32.5 cm); long narrow wings

    tail (interfemoral) membrane doesnot enclose the lower one-third toone-half of the tail, hence the namefree-tailed

    foot long, stiff hairs as long as thefoot protrude from the toes.

    Distribution (Fig. 6c)


    Dark brown or dark gray. Fur of someindividuals may have beenbleached to a pale brown due toammonia fumes from urine and de-composing guano.

    Confusion is not likely to occur withother speci