House Bat Management

by

Arthur M. Greenhall

U.S. Fish and Wildlife Service
Division of Wildlife Ecology Research
Washington, D.C. 20240

Abstract

The soundest long-term solution for the management of bats that enter buildings and cause a nuisance problem or present a public health hazard is by batproofing the structure. Chemical toxicants do not solve house bat problems and may create worse ones. This manual describes batproofing techniques that will provide effective and acceptable alternatives for dealing with house bat problems and hazards. Recent declines in bat populations and greater appreciation of the ecological importance of bats have identified the need for sound management strategies that will encourage bat conservation while protecting human health and solving nuisance problems. One of the best deterrents against house bats is to improve the energy efficiency of the structure since bats may enter holes through which heat is lost. Heat conservation methods used for batproofing will also be eligible for Federal residential energy tax credits. The manual should be useful to homeowners, public health officials, physicians, veterinarians, conservationists, and others interested or concerned about bat interactions with humans.

Table of Contents

• Foreword
• Introduction
• Review of Biology and Ecology of Insectivorous Bats
• Nuisance Problems
  • Why Bats Become a Nuisance
  • When Bats Cause Problems
  • Types of Bat Problems
  • Distribution of Problems
  • Confusion of Bat Problems with Those of Other Animals
• Species of Bats Causing Problems
  • Colonial Bats
  • Solitary Bats
• Public Health Hazards
  • Rabies in Bats
  • Histoplasmosis in Bats
• Bat Repellents
  • Chemical
  • Non-chemical
• Bat Toxicants
  • DDT
  • Anticoagulants
  • Fumigants
• Batproofing
  • Internal Revenue Service--Residential Energy Tax Credits
  • Location of Openings
  • Timing
  • Constantine's Batproofing Valve-like Device
  • Blocking and Sealing Holes
  • Batproofing Materials
  • Roofing
  • Walls
  • Church Steeples
  • Temporary Outside Roosts
• Bat Removal
  • Live traps
• Conservation
  • Artificial Bat Roosts
• Discussion and Recommendations
  • Bat Management Problems
  • Bat Conservation
  • Bat Management in Cities and Suburbs
  • Research Needs
  • Bat Management Legislation
• Acknowledgments
• References
• Appendix A. Identification of bats most often encountered by humans in houses
• Appendix B. Key to species accounts

Tables

• Table 1 -- Summary of 10 human cases of rabies attributed to exposure to insectivorous bats, United States and Canada, 1950-1979.
• Table 2 -- A summary of State bat legislation.

Figures

• Figure 1 -- Possible roosting sites in a house.
• Figure 2 -- Possible roosting sites in a cave and under rocks.
• Figure 3 -- Possible roosting sites in trees.
• Figure 4 -- Member of New York City's Bat Squad.
• Figure 5 -- Bats enter under eaves, at badly fitting ridge, and under shingles, slates, tiles.
• Figure 6 -- Blower door from Princeton University house doctor approach.
• Figure 7 -- Clothes hanger film-tissue air leak detector.
• Figure 8 -- Bendix/GASTEC Air Flow Indicator Kit.
• Figure 9 -- Smoke from the Bendix/GASTEC Air Flow Indicator makes it possible to visually determine the directional pattern of air currents.
• Figure 10 -- Constantine's batproofing valve-like device.
• Figure 11 -- Constantine's valve-like batproofing device placed in various installations.
• Figure 12 -- Types of weatherstripping.
• Figure 13 -- Nylon strip brush weatherstripping--"Therm-L-Brush."
• Figure 14 -- Ventilators should be properly screened.
• Figure 15 -- A properly insulated roof will keep bats out.
• Figure 16 -- Spanish or concrete tile roofing.
• Figure 17 -- Gaps under corrugated and galvanized roofing may be sealed with a self-expanding urethane foam, fiberglass, and resin.
• Figure 18 -- Types of traps that will collect house bats.
• Figure 19 -- Details of R. Davis' hopper trap.
• Figure 20 -- Effective bat trap.
• Figure 21 -- European bat houses.
• Figure 22 -- Artificial bat roost built by private citizens at Tea Lakes Wildlife Area near Rosebud, Missouri.
• Figure 23 -- Artificial bat refuge (bottom) at Tea Lakes Wildlife Area near Rosebud, Missouri.
• Figure 24 -- Little brown bat, Myotis lucifugus.
• Figure 25 -- Big brown bat, Eptesicus fuscus.
• Figure 26 -- Mexican free-tailed bat, Tadarida brasiliensis.
• Figure 27 -- Yuma myotis, Myotis yumanensis.
• Figure 28 -- Pallid bat, Antrozous pallidus.
• Figure 29 -- Silver-haired bat, Lasionycteris noctivagans.
• Figure 30 -- Red bat, Lasiurus borealis.
• Figure 31 -- Hoary bat, Lasiurus cinerus.