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What Is Happening to Bats on Mount Desert Island?

We all can help these important mammals to survive

By Bruce Connery
Fall/Winter 2013 Friends of Acadia Journal

The natural history of bats in Acadia National Park is not well known, having only been documented by a few studies (Zimmerman 1997, Divoll 2013) and the occasional observations of attentive naturalists. Ostracized by long-held and falsified fears, these little ecosystem managers of most of Mount Desert Island’s (MDI) habitats have gone on about their ecological duties without our support or caring since the departure of the glaciers. But their work and our concern changed recently when a fungus (Pseudogymnoascus destructans, the cause of “white nose syndrome”) introduced to North America in 2006, spread to Maine in 2010. In a little over a year it had reached Hancock County; its presence was confirmed by diagnostic testing on several deceased little brown bats (Myotis lucifugus) found in and outside the park. During the next few months, the park and Acadia Wildlife Foundation would receive or document more than 100 deceased individuals at more than 70 sites on MDI, illustrating both the extent of the outbreak and its wide distribution in a season when these insect-eating predators should have been in their sleep-like state of hibernation.

Several species of bats have been documented on MDI or in the area, but only five are thought to have been common summer residents before the outbreak. The most common of these species was the little brown bat, thought to have comprised approximately 40% of the bats observed every summer. The others were the northern long-eared bat (Myotis septentrionalis), the small-footed Myotis (Myotis leibii), the big brown bat (Eptesicus fuscus), and the red bat (Lasiurus borealis). Although they were known to spend the summers here, little was known of where they hibernated for the winter. Using ultra-sonic detections and trapping efforts conducted early in the spring and again in mid to late fall, Tim Divoll of the Maine-based Biodiversity Research Institute and park staff have shown that small-footed and big brown bats may winter on MDI, and that little brown and northern long-eared bats may roost in one or a few locations very close to the Island. These study findings also showed that at least the small-footed Myotis use the Island to give birth and raise their pups.

Since the original discovery of the fungus, surveys by park biologists and Divoll have documented drastic declines in the populations of little brown and northern long-eared bats across MDI. The fungus also appears to have infected a significant number of small-footed Myotis (see picture of damaged wing membrane), although the effect on the population is unclear. If the declines found in these studies are real, biologists expect significant ecological changes in most of the forest, marsh, and shrub-land habitats that could become apparent in many direct and indirect effects on Maine’s economy (e.g., tourism, forest products, and agriculture). Less natural control of insects by bats would directly translate to significantly higher numbers of insect pests surviving in agricultural areas, forest and wetland habitats, and in many urban and rural landscapes used by humans. These concerns are valid for Acadia and for all of Maine, making the loss of bats much more serious than just the loss of species and biological richness.

In the last five years, dozens of research efforts have searched for answers to the life history of the fungus, how it affects bats, how it has spread so quickly in North America, and how it might be controlled or eliminated. These findings have helped us understand the disease and increased our understanding about bats immensely (see reference sources at the end of this article), but have found no solutions to stop the declines in bat populations. During this time, biologists and scientists have identified ways to protect remaining individuals and entire populations by applying the same safeguards used in any disease outbreak. While some of these wouldn’t apply to MDI or Acadia, others such as carefully timing the construction or remodeling of roofs and attics and access to these areas are seen as an important step in limiting the possible transfer of the fungus’ reproductive spores to new populations.

Bat house located on MDI. NPS photo.Much remains to be done on MDI, in Acadia, and across Maine. Anyone can be part of the effort to help bats by doing one or more of the following:

Natural areas:
1. During late fall (November), through the winter, and into the spring (April), report to the park biologist (find contact information at the end of the article) any observations of bats that are outside, whether flying or on buildings or on the ground. These observations will help park and Maine state biologists map the location of bats apparently affected by the disease, and can be used to pinpoint possible summer or winter roosts that may be infected with the disease. Remember to record date, time of day, activity of the bat(s), and the specific location. Don’t try to capture or collect the bat unless you have talked with the park or Maine state biologist or someone at Acadia Wildlife Foundation. If pictures are possible, please take one or more and send these to the park biologist.

2. If you find a bat on the ground or on the lower levels of a building wall, exterior or interior, please contact the park biologist or someone at Acadia Wildlife Foundation for information or directions on what can be done. Don’t disturb or handle the bat unless you believe it is in danger, and then only with gloved or covered hands to a safe, dark, and more protected location.

Buildings, whether home, storage, or work:
1. Consider putting bat houses near your home, business, or any areas you maintain. The current thinking is that bats that have survived in an infected area may have or develop some immunity to the fungus. Providing them with new roost locations will give these remaining individuals a safe and uninfected area to roost in during the summer. Follow guidelines (see reference sources at the end of the article) about the design and construction of the bat house; its color and placement on the exterior of a building, pole, or tree; and its orientation to the sun, height above the ground, and placement in a habitat. The park and other federal agencies, Maine Department of Inland Fisheries & Wildlife (DIFW), and many private bat organizations have information to help you with all of these considerations.

2. If you are planning siding or roof fixes to your house, storage area, or any building, or considering other substantive or cosmetic fixes, please contact Maine DIFW about when these activities should be conducted. Avoiding the weeks before and after the young are born but before they learn to fly gives young bat pups a better chance to survive once they leave their maternal roost and become independent. All of Maine’s bats have only one pup a year, and not necessarily every year, meaning rebuilding Maine’s bat population will take many years—likely decades. For these reasons, Maine DIFW has regulations that prohibit contractors from doing this type of work during late May to mid-July, and Maine towns are to enforce this regulation by not issuing building permits during this time. Do-it-yourself homeowners should also follow these construction and remodeling dates.

3. Equally important is to limit activity in an attic or upper loft of garages or other storage buildings during the maternity period. By staying away from possible roosts from late spring through mid-July, you will again be supporting the wellbeing and recovery of Maine’s bats.

Bruce Connery is the park biologist at Acadia National Park. He can be reached at 288-8726 or to report bat-related information.


Information on Pseudogymnoascus destructans (formerly known as Geomyces destructans):

Information on bats:

Information for Maine:

Maine Department of Inland Fisheries & Wildlife:
Acadia Wildlife Foundation: call 288-4960