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Watershed, Fish, Wildlife, Air & Rare Plants

Bats: Masters of the Night Skies

The Battle For Bats

Bats are in serious decline nearly everywhere. Worldwide, there are almost a thousand different kinds of bats which comprise nearly 1/4 of all mammal species. Of the 43 species living in the U.S. and Canada, nearly 40 percent are endangered or are candidates for such status. The biology and ecology of bats is not well understood. Their nocturnal behavior, inaccesible breeding and roosting sites, and migratory behavior have made them difficult to study. As a result, we know little of bat ecology or management needs on public lands. Despite a lack of knowledge, we do know that bats often use trees, cliffs, caves, human dwellings, natural waters and water developments, bridges and mine shafts in a variety of habitats. There are clearly opportunities to begin specific management actions to protect or enhance this diverse and threatened group of mammals.

One method that the Forest Service is using to protect critical bat habitats is the installation of iron grates over abandoned mine entrances. These "bat-gates" serve two primary purposes: they protect the public from stumbling into a mine that might be dangerous, as well as protecting habitat allowing passage for bats. In the past, many abandoned mines have been filled in with earth, often a costly proposition that is deadly for bats. Maintaining the mine for bats provides a win-win situation that is both simple and cost-effective. With approximately 25,000 abandoned mines on Forest Service lands and an estimated 200,000 across the U.S., there is great potential to make a significant positive impact on bat populations through this method of protection.

Spot Light

Bat Conservation International and USDA Forest Service Sign MOU
Dr. Merlin Tuttle, President/Founder Bat Conservation International, Inc. and Deputy Chief Joel Holtrop recently signed a new Service-Wide Memorandum of Understanding (MOU, enclosure). This MOU recognizes our longstanding partnership and mutual interest in the conservation and management of bats, their habitat and associated ecosystems, and our common desire to expand our cooperative work.

Bat Conservation International’s (BCI) mission is to protect and restore bats and their habitats worldwide by helping people understand and value bats as essential components of ecosystems. BCI advocates protecting critical bat habitats, advancing scientific knowledge about bats and their conservation needs, and facilitating management approaches that help both bats and people.

The Forest Service has a proven track record of working in collaboration with BCI, focusing especially on helping employees to understand and value bats as essential allies in managing habitats, and advancing scientific knowledge about bats, conservation needs, and ecosystems through continuing education, training, and cooperative research. By managing for bats and their habitats, the Forest Service contributes to conservation of the nation’s biodiversity, creating a healthier environment for both wildlife and people.

Investing in partnerships takes time, effort and energy—but it is worth it, and is in the Forest Service’s and the public’s interest. Partnerships such as these allow the Forest Service to effectively do more of the important conservation work that benefits the public’s resources.

Thanks to all who contributed to preparation and review of this MOU!

MOU with BCI and FS 41.4 KB PDF
Letter Announcing BCI-FS MOU 25 KB PDF
Partnership Opportunities with BCI 47 KB PDF


Photograph: Big Brown Bat.  Photo taken by Dennis Krusac, USFS, R8Big Brown Bat
Taken by Dennis Krusac, USFS

Save the Planet with BATS - 2008 Bat Blitz on the Bankhead NF
An excellent piece, featuring our own (!) Dennis Krusac, Region 8 biologist, is featured in this segment. Channel 42 in Birmingham, Alabama is covering the 2008 Bat Blitz in the Bankhead National Forest. There are a few errors, like there are in any news story, but it is a good story. The film crew from Discovering Alabama was at the blitz all 4 days and they are planning an entire show on bats. Don not know when the 'Discovering Alabama' show will be available, but it should be very good.

Links to Channel 42:

http://www.cbs42.com/news/local/26911414.html
http://www.cbs42.com/news/features/7209481.html?articleID=6265

Abandoned Mines - Bat Barracks

Abandoned mines have become key year-round resources for bats. Mines seem to be most important for rearing young in summer, for hibernating in winter, and for use as temporary rest stops during migration. Throughout the United States, human disturbance of caves, cave commercialization, deforestation, and urban and agricultural development have forced many bats from their traditional roosts in search of new homes. Old mines are often the only suitable temperature-controlled shelters left midway between a bat's summer and winter roosts; without these protected resting places, many species' migratory mortality could greatly increase. Over the past 100 years or more, displaced bats have gradually moved into many mines. In more than 6,000 mines surveyed by researchers in Arizona, California, Colorado, and New Mexico, 30 percent to 70 percent in each state showed signs of use by bats. An average of 10 percent contained important colonies. From the Great Lakes Region eastward in the U.S., up to 70 percent of subsurface mines may be used by large bat populations. Bats, due to their colonial nature, are especially vulnerable during hibernation both to vandals, and to rapid mine closures. The largest recorded hibernating population of western big-eared bats was recently destroyed in a New Mexico mine shaft where vandals had set old timber on fire. In New Jersey, the state's largest population of hibernating bats was inadvertently trapped in the Hibernia Mine when it was capped. Had state biologists not convinced state authorities to reopen the entrance immediately, these bats would have perished. Likewise, the Canoe Creek State Park limestone mine in Pennsylvania was reopened in the nick of time to save its bats and now shelters the largest bat hibernating population in the state. Clearly, the difference that protecting and stabilizing just one mine shaft can make is tremendous.

Bats Are A Big Deal

Bats are a primary predator of vast numbers of insect pests that cost farmers and foresters billions of dollars annually. Bats also pollinate flowers and disperse the seeds that make the rain forests grow and the deserts bloom. Wherever bats are found, they are critical elements in nature's delicate web of life.

How YOU can help bats

  • Contact your State Department of Natural Resources about area mines and bat gaiting.
  • Join Bat Conservation International.
  • Ask your local Forest Service office about volunteer opportunities.
  • Ask your local Forest Service office or Bat Conservation International about them hosting the "Bat Cave" interactive educational unit at your local school(s). (The "Bat Cave" is still under construction by the Forest Service. Once the parts and pieces are assembled into a traveling unit it will be shipped to Bat Conservation International for review, improvement and management.)
  • Build or buy a bat house and put it up in your yard. Contact Bat Conservation International about optimal placement.
  • Help your neighbors learn about bats and their benificial role in nature.
  • Don't trap bats in your attic. Wait for the bats to leave at night to go feeding and then close up the holes in your attic. Contact Bat Conservation International for further information.
  • Read books about bats. Visit your public library or other bat web sites.
  • Ask the Experts at Scientific American
  • Adopt a Bat!

You can also find locations for viewing wildlife, plants and fish through our NatureWatch website (www.fs.fed.us/outdoors/naturewatch/where-to-go.php).

Bat Biology

Echolocation (borrowed from Scientific American, "Ask the Experts") How do bats echolocate and how are they adapted to this activity?

Alain Van Ryckegham, a professor at the School of Natural Resources at Sir Sandford Fleming College in Lindsay, Ontario, Canada, offers this explanation: Bats are a fascinating group of animals. They are one of the few mammals that can use sound to navigate--a trick called echolocation. Of the some 900 species of bats, more than half rely on echolocation to detect obstacles in flight, find their way into roosts and forage for food.

Echolocation--the active use of sonar (Sound Navigation AndRanging) along with special morphological (physical features) and physiological adaptations--allows bats to "see" with sound. Most bats produce echolocation sounds by contracting their larynx (voice box). A few species, though, click their tongues. These sounds are generally emitted through the mouth, but Horseshoe bats (Rhinolophidae) and Old World leaf-nosed bats (Hipposideridae) emit their echolocation calls through their nostrils: there they have basal fleshy horseshoe or leaf-like structures that are well-adapted to function as megaphones.

Echolocation calls are usually ultrasonic--ranging in frequency from 20 to 200 kilohertz (kHz), whereas human hearing normally tops out at around 20 kHz. Even so, we can hear echolocation clicks from some bats, such as the Spotted bat (Euderma maculatum). These noises resemble the sounds made by hitting two round pebbles together. In general, echolocation calls are characterized by their frequency; their intensity in decibels (dB); and their duration in milliseconds (ms). In terms of pitch, bats produce echolocation calls with both constant frequencies (CF calls) and varying frequencies that are frequently modulated (FM calls). Most bats produce a complicated sequence of calls, combining CF and FM components. Although low frequency sound travels further than high-frequency sound, calls at higher frequencies give the bats more detailed information--such as size, range, position, speed and direction of a prey's flight. Thus, these sounds are used more often.

In terms of loudness, bats emit calls as low as 50 dB and as high as 120 dB, which is louder than a smoke detector 10 centimeters from your ear. That's not just loud, but damaging to human hearing. The Little brown bat (Myotis lucifugus) can emit such an intense sound. The good news is that because this call has an ultrasonic frequency, we are unable to hear it. The ears and brain cells in bats are especially tuned to the frequencies of the sounds they emit and the echoes that result. A concentration of receptor cells in their inner ear makes bats extremely sensitive to frequency changes: Some Horseshoe bats can detect differences as slight as .000l Khz. For bats to listen to the echoes of their original emissions and not be temporarily deafened by the intensity of their own calls, the middle ear muscle (called the stapedius) contracts to separate the three bones there--the malleus, incus and stapes, or hammer, anvil and stirrup--and reduce the hearing sensitivity. This contraction occurs about 6 ms before the larynx muscles (called the crycothyroid) begin to contract. The middle ear muscle relaxes 2 to 8 ms later. At this point, the ear is ready to receive the echo of an insect one meter away, which takes only 6 ms.

The external structure of bats' ears also plays an important role in receiving echoes. The large variation in sizes, shapes, folds and wrinkles are thought to aid in the reception and funneling of echoes and sounds emitted from prey. Echolocation is a highly technical and interesting tactic. To truly understand the concepts and complexity of this subject is to begin to understand the amazing nature of these animals.

Ecoholocation Calls Library - University of New Mexico Bat lab, the bat ecology and bioacoustics lab - University of Bristol Adopt a Bat - Bat Conservation International

References:

  • Bats, M. Brock Fenton
  • Bats: A natural history, John Hill and James D. Smith (ISBN 0-292-73070-5)
  • Bats of the Eastern United States, Michael J. Harvey, Published by Arkansas Game & Fish Commission (February 1992)
  • The Fascinationg World of ...Bats, Maria Angels Julivert (ISBN 0-8120-1953-9)
  • Extremely Weird: Bats, Sarah Lovett (ISBN 1-56261-008-2)
  • America's Neighborhood Bats: Understanding and Learning to Live in Haromy with Them, Merlin D. Tuttle (ISBN 0-292-70406-2)



Disclaimers | Freedom of Information Act (FOIA) | Privacy Notice

Watershed, Fish, Wildlife, Air & Rare Plants (WFW)
Washington, D.C. Office
Author: Shelly Witt, National Continuing Education Coordinator, WFW staff
Email: switt01@fs.fed.us
Phone: 435-881-4203
Publish_date:1/20/99
Expires: none

Photo Credits

USDA Forest Service
P.O. Box 96090
Washington, D.C. 20090-6090
(202) 205-8333