Monday, November 14, 2011

Changing Adirondack Bat Populations

Interest in bats has steadily increased over the past several years as the problem of white-nose syndrome has become more acute, especially in the Adirondacks. As people become more familiar with this unique group of mammals, numerous questions regarding their ability to survive the ravages of this rapidly spreading disease continually arise.

While there are answers to a few questions, most have none, other than “best guesses” or “ideas” from very intelligent wildlife biologists who have regularly studied these creatures. However, even the experts are limited in responding to some questions about bats, as there has not been much research conducted into numerous aspects of their natural history and population status, especially here in the Park. Although some features of bats are well known, many habits and behavioral traits of these winged animals still remain a mystery.
One question from last week that I would like to address is, “Are ALL Adirondacks bat species disappearing?” The answer simply is that it is impossible to say. Information on the status of bat populations comes mainly from surveys routinely conducted during the winter in caves and mines that are known as primary hibernating sites. (You can read Phil Brown’s article that appeared in the Almanack this past January on this method of data collection.)

However, there are three species of bats, the silver-haired bat (Lasionycteris noctivagans), red bat (Lasiurus borealis), and the hoary bat (Lasiurus cinereus) in the Adirondacks that migrate southward during the autumn rather than enter these caves and mines. Far less information has been collected by researchers regarding their population status in the Park. As a result, it is difficult to assess how these species are faring during this outbreak of white-nose syndrome. As far as I have been able to determine, there has not been a single reported case of this bacterial infection in any of these three species of bats.

Because the bacteria responsible for white-nose syndrome (Geomyces destructans) seems to be confined to caves and mines, it is possible that these three species may never be impacted, but that is just a “guess” at this point in time. It is also possible that even these bats over a long period of time may eventually experience encounters with individuals of other species that are carrying the disease, and transmission may occur.

Some big brown bats (Eptesicus fuscus), as I mentioned last week, also fail to use caves and mines for their hibernating site. The percentage of big brown bats in the Adirondacks that actually use caves and mines contaminated with the bacteria Geomyces destructans versus places that are free of this disease is unknown. Similarly, the northern long-eared bat (Myotis septentrionalis) on occasions has been reported to use sites other than caves and mines in which to hibernate. Several individuals of this species have been found spending the winter in basements, abandoned wells, and storm sewers that run deep underground, yet it is unknown how common a practice this is among this species of bat.

In a series of articles about bats that appeared around this time last year, Ellen Rathbone referred to a summertime collection of population data using sophisticated, sound monitoring devices. Over a period of time, this technique will provide some meaningful insight into the status of bat numbers in the Park which could help answer the question as to what species may be declining, and which species, if any may be expanding their numbers.

When Merriam conducted the first survey of bats in the region during the late 1800’s, he concluded that the most common species by far was not the little brown bat but the silver-haired bat.

Our environment is always in a state of change. As one population goes down, another eventually expands and fills its role in our complex food web. And just because the numbers of one animal species are down does not mean it will eventually become extinct. All creatures have an immune system, and while a disease may be lethal to a substantial portion of the population, it does not mean that it will wipe out ever individual in that species. More research into the lives and status of bats is needed, particularly here in the Adirondacks.

Photo: Merlin Tuttle, Courtesy Bat Conservation International

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Tom Kalinowski

Tom Kalinowski is an avid outdoor enthusiast who taught field biology and ecology at Saranac Lake High School for 33 years. He has written numerous articles on natural history for Adirondack Life, The Conservationist, and Adirondack Explorer magazines and a weekly nature column for the Lake Placid News. In addition, Tom’s books, An Adirondack Almanac, and his most recent work entitled Adirondack Nature Notes, focuses on various events that occur among the region’s flora and fauna during very specific times of the calendar year. He also spends time photographing wildlife. Tom’s pictures have appeared in various publications across the New York State.

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