BATS GOING EXTINCT?
September 5, 2010
I have received
the following questions about bats during the last few weeks.
Q. How many
kinds of bats live in the United States? Do they only come out at night?
I am sure I saw one last week before dark.
than 35 different species of bats are found in the United States if several
tropical species that enter some of the southwestern states are included.
A half dozen U.S. species are widespread, ranging from coast to coast
and from Canada to the Gulf States. And about half a dozen species have
geographic ranges that are restricted to the United States, the vast majority
being found also in Canada, Mexico, or both. Bats are able to be completely
nocturnal by using supersonic sound production that allows them to find
insect prey and avoid physical structures with echolocation. However,
bats have tiny eyes and can see in the daytime; they are occasionally
active an hour or so before dark and after sunrise.
Q. Is it
true that a disease is driving the country's bats to extinction?
biologists are especially concerned about a type of fungus that can grow
on the exposed skin of bats and cause death during hibernation. The disease
is known as white-nose syndrome because the fungus is whitish and the
nose of most bats is exposed and likely to be attacked. The origin of
the fungus is unknown but has been found on bats in Europe. Some scientists
believe it may have originated there and has now become an invasive species
in North America. Because U.S. bats have not been exposed previously to
the fungus and thus have evolved no natural immunity, white-nose syndrome
has been devastating to bat colonies.
A study conducted
by Boston University's Winifred F. Frick and other scientists ascertained
the extent and potential impact of white-nose syndrome on selected species
of U.S. bats. They used research data collected for 30 years on bat colonies
at more than 20 hibernation sites, including caves and mine shafts as
far south as West Virginia. The first discovery of white-nose syndrome
in U.S. bats was in a New York cave five years ago. Since then the disease
has spread like an epidemic, resulting in the deaths of more than a million
bats in 14 eastern states, from Maine to Tennessee. More than nine bat
species have been found to be susceptible to the invasive fungus, and
projections are that the epidemic will spread to bat hibernation sites
from the Carolinas to Alabama.
her colleagues focused part of their study on a particular species known
as the little brown bat, or little brown myotis. Many people have seen
little brown bats at one time or another as it is one of the most widespread
and common bat species in the country, with more than 6 million individuals.
They range from eastern Canada to Alaska to California to the Southeast.
An estimate of flying insects, including mosquitoes, eaten by little brown
bats in a year would certainly number in the millions and be measured
in tons by weight.
have found that little brown bats are highly susceptible to white-nose
syndrome and that the disease is present in more than 100 hibernation
sites they examined. Unfortunately, they found that the mortality rate
averaged more than 70% across the colonies and as high as 99% in some.
The really bad news is their prediction that little brown bats regionally
affected by the fungus will go extinct in only 16 years. The implications
that similar responses might be seen in other species of bats and in other
parts of the country are disquieting.
about white-nose syndrome underscore how serious introduced, invasive
diseases can be to native species that have no evolutionary experience
with them. The fact that we could lose an important component of our natural
ecosystems, especially one that eats so many mosquitoes, is not a pleasant
one. Let's hope that further research will offer solutions for ways to
control the spread and impact of the deadly fungus.
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